Bicycle Plan - Part 6

Traffic Calming

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The objective of this chapter is to identify prototype traffic calming measures to apply in San Francisco in order to make bicycling safer and more convenient.

Traffic Calming is the term applied to a variety of physical measures intended to reduce the dominance of automobile and truck traffic in urban areas. Traffic calming measures can be applied as spot improvements to treat an existing problem, such as speeding, or along a corridor to create a bicycle-preferential street, called a bicycle boulevard. Traffic calming does not attempt to ban the automobile, but primarily to reduce the speed of automobile traffic. In some applications, traffic calming measures are employed to reduce "through" or non-neighborhood traffic on certain streets. Aiming for one of these goals usually has the desirable secondary result of achieving the second goal and discouraging the use of the automobile altogether.

Traffic calming measures are virtually all very positive (or at worst neutral) to pedestrian circulation. The resultant traffic noise, speed and air pollution reductions create safer, more attractive, and more livable residential areas. However, if not done with care, traffic calming can adversely impact bicycling at the same time that it reduces auto speeds and/or volumes. On the other hand, traffic calming can be designed to promote bicycling simultaneously with walking and transit.

The goal of this study is to specifically encourage bicycle traffic, not to explicitly slow, discourage or reduce auto traffic. Bicyclists can share the general benefits of traffic calming if the City is selective about the strategies used and of the measures are carefully designed. If not, there may be disadvantages to bicyclists as well. Traffic calming measures are advantageous to bicyclists if they do one or more of the following:

* Slow vehicular traffic to a speed of 25 mph or less.

* Slow all traffic on a street to a reasonable bicycle speed (about 15 mph), thereby calming vehicular traffic without significantly affecting the majority of bicyclists.

* Eliminate impediments to bicycle travel, particularly STOP signs (if a traffic engineering study confirms that it is safe to do so).

* Exempt bicycles from the more restrictive measures, such as the provision of a cyclist bypass through a barrier.

Traffic calming measures that accomplish these objectives can create streets that have less vehicular traffic than adjacent streets, slower speeds, or both, while remaining efficient for and attractive to bicyclists. Such streets are especially suitable for children, inexperienced adults, casual and recreational bicyclists, and others who lack the skill, confidence, or desire to travel on fast, direct routes that also carry heavy vehicular traffic.

Streets that are traffic-calmed specifically for bicycles are referred to generically in this chapter as bicycle priority streets. They are one element of the proposed San Francisco Bikeway Network that also includes bike lanes, bike paths, and streets with wide curb lanes. They are considered a critical component in inducing casual and novice cyclists to begin bicycling, as they provide a low traffic, stress-free, un-intimidating environment for bicyclists. To provide safe, convenient, attractive routes for these riders, as well as a less stressful alternative for experienced cyclists, bicycle priority streets are an essential component of the comprehensive bikeway network. In some cases a traffic-calmed street may be a significantly improved alternative for experienced cyclists as well. It is impractical to expect that all of a cyclist's trips can take place on a bicycle priority street. But for those routes that serve a particular cyclist's destination, whether he/she be experienced, novice, or child, bicycle priority streets are irreplaceable.

In addition, by slowing vehicular traffic to posted speed limits, safety is dramatically improved for bicyclists and pedestrians. Studies have shown that the probability of surviving a motor vehicle collision increases dramatically for motor vehicle speeds under 30 mph. Thus, traffic calming can also be used to benefit bicyclists (and pedestrians) by incorporating design features on most or all city streets that discourage automobiles from travelling over 30 mph.

Traffic calming has been used with great success in Western Europe, often in compact, dense urban areas similar to San Francisco. It has many proponents in the United States, notably a group called Sensible Transportation Options for People (STOP) in Portland, Oregon. Many bicyclists endorse traffic calming measures (including the San Francisco Bicycle Coalition).

It is beyond the scope of this chapter, or of the Comprehensive Bicycle Plan itself, to evaluate or recommend specific traffic calming plans for San Francisco. Instead, this chapter focuses on the following narrower issues:

* Does traffic calming have advantages for bicyclists?

* If so, which traffic calming techniques are helpful to bicyclists, which are neutral, and which should be avoided?

* How can traffic calming ideas be adapted specifically for the benefit of bicyclists?

* Which streets, if traffic-calmed, would benefit bicyclists the most?

The remainder of this chapter discusses the evolution of traffic calming, applies the concept of Traffic Calming to bicycle priority streets, lists the streets or corridors in San Francisco that could most benefit from traffic calming, describes traffic calming strategies that are compatible with bicycles, and lists criteria for selecting routes for bicycle priority treatment through traffic calming.

Strategies to implement bicycle priority streets in San Francisco will be presented at the end of this chapter.


Although traffic management techniques of various kinds have been used for decades, modern traffic calming began with the pedestrianization of downtown shopping areas in Germany during the 1960s. Vehicles were excluded completely, and the streets were reserved for pedestrians. As a result of the economic success of these areas and their contributions to historic preservation, pedestrianization of downtowns became the standard practice. In former West Germany, there are now over a thousand central district pedestrian areas. Nearly all cities with a population of over 50,000 have them, as do three-quarters of those with populations between 20,000 and 50,000. These areas range in size from 100 meters to many kilometers.


Complete or nearly complete pedestrianization often implemented in commercial/retial areas. Pedestrian-only areas are particularly feasible in commercial or retail districts where customers and employers arrive via non-auto modes and where deliveries can be made through rear entrances or at off hours. It is less practical in residential neighborhoods, where residents require access at least for their own and visitors' vehicles.

To achieve a pedestrian ambiance while not banning the automobile outright, in the 1970s the Dutch invented the woonerf, or "living yard" (plural woonerven), an area that can be shared by pedestrians and vehicles. The woonerf is designed primarily for pedestrians, who have use of the full right-of-way; children may even play there. Typical design elements of a woonerf include:

* Planters, benches, parking bays, or other obstacles that force vehicles to traverse a narrow and meandering path at a slow speed

* Varied paving materials

* No continuous roadway or footway markings or surface height differences that would segregate pedestrians and vehicles

Within the woonerf motorists must drive at a walking pace and may not hinder pedestrians. These design features, and the idea that autos do not have the right of way, have subsequently been extended to winkelerven (shopping streets) and dorpserven (village centers).

Evolution of Traffic Calming Measures

Woonerven have strict design requirements, are expensive to construct, and are suitable primarily for low-traffic streets. Following the success of woonerven, Dutch and German traffic planners and engineers in the 1980s developed more general techniques for reducing traffic speeds below 30 km/h (18 mph) over a wide area, without the expense of woonerven or the loss of continuity that road closures or one-way streets would bring. The term "traffic calming" is a literal translation of the German "Verkehrsberuhigung." The array of available techniques is discussed in detail below. Pedestrianization and traffic calming techniques have already become widespread throughout Europe and also in Japan. In France and Denmark, these techniques have been adapted to major as well as to minor roads.

In the United States, traffic calming often goes under the name of neighborhood traffic management. Neither the breadth nor the depth of schemes used here approaches their European counterparts, but many of the ideas discussed below have been applied from time to time. The same principles have also begun to see application in areas beyond traffic control. Oscar Newman, an architect and urban planner at Washington University in St. Louis, contends that quiet, private streets can create a sense of community, prevent crime, and reverse urban decay.

In 1992, following a plan developed by Newman, the Five Oaks area of Dayton, Ohio, installed speed humps and barriers, pedestrianized streets and alleys, and erected brick and metal gateways. One large neighborhood was divided into eleven mini-neighborhoods, each physically separated from the rest and accessible only from peripheral arterials. The smaller neighborhoods were intended to enhance the sense of community and discourage outsiders, including those with criminal intent, from wandering undetected into the area. Traffic in the Five Oaks area declined by 67 percent, total crimes by 26 percent, and violent crimes by half; remarkably, crime in other areas not did increase. Newman is currently developing a plan for Seattle neighborhoods, and Richmond, CA has also considered adopting his ideas.

In 1991, the City of Portland, Oregon convened a neighborhood congress of 250+ neighborhood leaders to develop a comprehensive plan to control neighborhood traffic. Four major areas of concern were identified:

i. Traffic speeds and volumes;

ii. Bicyclist and pedestrian safety;

iii. Drunk driver and seat belt issues; and

iv. Alternate modes of transportation.

The draft plan contained over 350 specific objectives and action statements. The plan was published in February 1993, and many streets have since been "calmed" using techniques such as traffic circles, speed humps and median strip barriers.

Traffic Calming in the 1990s

Traditional transportation planning and traffic engineering strive to facilitate traffic flow by increasing capacity and speed. Traffic calming, on the other hand, attempts to slow traffic down. Rather than a direct, straight route, it may provide a circuitous or winding one; rather than wide lanes, narrow lanes; rather than a smooth surface, a rough surface.

The aim of traffic calming is not necessarily to impede motorized travel; a substantial reduction in speed often results in only slightly increased travel times, because the traffic flows more freely. By eliminating delays at stop signs and signals, devices such as traffic circles can decrease travel time even though the average speed of moving vehicles is reduced.

MotoristsCand people in generalCseem to be willing to tolerate a certain amount of risk in exchange for a corresponding benefit. (This statement does not imply that people are always accurate, or even rational, in evaluating risks.) Speed limits on both state highways and local roads, for instance, are determined on the basis of an engineering and traffic survey. The Caltrans Traffic Manual's standards for the survey assume that 85 percent of drivers travel at or below the safe speed for prevailing conditions, and that, in the absence of unforeseeable hazards, their judgment and experience should be relied on to set the speed limit. The California Vehicle Code expressly states that physical conditions such as width, curvature, grade, and surface, or any other condition readily apparent to a driver, are not grounds for lowering the speed limit.

Thus, while widening and straightening a roadway might be expected to reduce the accident rate, it may instead increase the average speed, since drivers can now travel faster at the same level of risk. Supporters of traffic calming therefore argue that the safety promised by traditional facility improvements is illusory. On the other hand, this argument can also be reversed: lowering the safety limit of the design may decrease speeds (precisely because drivers recognize where this limit lies), but they will adjust their speeds downward only enough for the risk to remain more or less constant. Facilities alone cannot force drivers to operate below this level of risk, and neither can enforcement without changes in current law governing allowable speed limits.

It is true, nevertheless, that while lower speeds may not lead to a decrease in accident rate, they do lead to a decrease in accident severity. There also seems to be a substantial psychological benefit to pedestrians and bicyclists.


Traffic and Socio-Economic Impacts

According to its supporters, the ultimate purpose of traffic calming is to maximize mobility while reducing the undesirable side effects of mobility based exclusively on the private automobile. These side effects can include, directly or indirectly:

* Constant and excessive noise;

* Air pollution and its medical consequences;

* The injuries and deaths caused by traffic accidents, including many to pedestrians and bicyclists;

* Devotion of substantial quantities of precious land to roads and to on-street or off-street parking;

* Destruction of houses, neighborhoods, historic buildings, and natural features for highways;

* Urban sprawl, leading to further reliance on the automobile;

* Traffic congestion and long commutes for motorists;

* Heavy traffic on residential streets;

* The decline of public transit;

* Loss of mobility for the poor, the elderly, the disabled, and children;

* The aesthetic poverty of masses of asphalt, concrete, and metal;

* Crime and fear of crime;

* Dependence on oil companies and oil-producing nations;

* Large personal expenses to buy and maintain automobiles;

* A sedentary lifestyle;

* The expense to government of planning, building, maintaining, and policing roads;

* The expense of providing utilities and services to a spread-out city;

* Deterioration of central and neighborhood business districts that have become difficult to reach;

* Loss of sales tax revenue;

* Decreased personal and commercial property values;

* Loss of property tax revenue;

* Further loss of tax revenue as land is taken out of service for roads and parking; and

* Loss of the conditions for and a sense of community.

Bicycles and Traffic Calming

Even from this brief history, it is clear that pedestrianization, woonerven, and traffic calming serve primarily to control automobile traffic for the benefit of pedestrians. Bicycles are considered, if at all, only as an afterthought, and if so are generally treated as if they traveled short distances at pedestrian speeds. This approach is inappropriate to conditions in the United States, including San Francisco. It is therefore useful to examine whether traffic calming does benefit bicycles, whether it has inadvertent side effects, and whether its techniques can be modified to bicyclists' advantage.

Benefits - Traffic calming can reduce traffic volume, traffic speed, and accident rates, but its direct effect on bicyclists have received little attention and has not been well documented. Case Study No. 19 of the Federal Highway Administration's National Bicycling and Walking Study, Traffic Calming, Auto-Restricted Zones and Other Traffic Management Techniques - Their Effects on Bicycling and Pedestrians, despite its title, reports only a small number of observations:

* In the small town of Buxtehude, Germany, bicycle use doubled in the four years since a traffic calming project was finished. Bicycle accidents also rose, but they were primarily non-injury accidents. The fractions of accidents in which bicyclists were at fault fell from 45 to 35 percent.

* In the Berlin-Moabit area, bicycle use increased by 50 percent, and there was a 16 percent reduction in cyclist accidents.

* In the Koraku section of Minato-ku, Nagoya, Japan, bicycle volume rose along most traffic-calmed routes.

* Groningen, the Netherlands, divided its central area into traffic cells whose boundaries private motor vehicles were not permitted to cross. To travel from one cell to another, drivers must return to a ring road. Bicycling increased substantially, and now constitutes over 50 percent of all trips.

* Bicycle use doubled between 1976 and 1986 in the city of Freiburg, Germany, which has an extensive network of pedestrianized streets, traffic-calmed streets, and bike paths.

* In Vinderup, Denmark, the speed limit on a through road was lowered to 40 km/h (24 mph), and bike paths were constructed along it. Seventy-five percent of bicyclists reported feeling safe riding on the street, compared to 17 percent before the changes (although it is not clear whether the bicyclists were referring to the street or the paths). In addition, 54 percent thought it was easier to cross the road. In Skaerbaek, where similar changes were instituted, bicyclists reported it is had become easier to cross the road, although it took longer to do so.

* Bicycle traffic on the Palo Alto Bicycle boulevard almost doubled over previous levels, and anticipated problems failed to materialize. The bicycle boulevard is discussed at length later in this chapter.

* Bicycle traffic increased on the Berkeley slow street. The bicycle community was reluctant to endorse speed humps, although they had no documented adverse effects.

* Bicyclists felt adversely impacted by STOP signs introduced for neighborhood traffic management in St. Paul Minnesota.

It is plausible that a decrease in motor vehicle volume and speed would reduce the chance of car-bike collisions, everything else being equal (which is not necessarily the case), however, the hard evidence for improved safety must be considered slight. However, these accounts do show a clear change in bicycle use and in bicyclists' perception of road safety.

Potential Drawbacks - Traffic calming in and of itself is not a panacea for bicycle travel. Bicyclists, particularly experienced bicyclists, can get about efficiently on existing roadways, if (and it's a big if) they are given reasonable surface quality and lane-sharing width. It is not enough by itself, because it does not guarantee surface quality or route directness and continuity. At times it may not even be beneficial, because:

* Traffic calming may restrict the movement of bicyclists as well as motorists.

* Traffic calming may force bicyclists to share road space with pedestrians, although their speeds and movements are very different.

* Traffic calming design features may inadvertently inconvenience or even endanger bicyclists.

Conclusion - If used properly, however, traffic calming can provide routes that are attractive to the majority of bicyclists. In addition, it must be acknowledged that there is a class of bicyclists, (much larger than the existing number of bicyclists in San Francisco) that would ride on traffic-calmed bicycle priority streets but not on major arterials no matter how wide the lane or bike lane. These bicyclists include casual or novice adult riders and children and young teens.


The Original Bicycle Boulevard

The first bicycle priority street, called a Bicycle Boulevard, was created in Palo Alto in 1982 along a two-mile section of Bryant Street, a local residential street that is about 36 feet wide. Most of the STOP signs on Bryant Street were removed, and two-way stops were placed on cross streets instead. Bryant Street's intersections with collectors were made four-way stops. Bryant Street intersects one arterial, Oregon Expressway, at an intersection that was already signalized.

These changes created a through route that would have been very attractive to automobiles as well as bicycles, except that it was already interrupted at one point by a natural road closureCa creek that was crossed only by a narrow footbridge usable by bicycles. Two road closures were added at other points along Bryant Street to discourage traffic on the rest of the route. The closures consisted of horizontal wooden power poles placed on the pavement; bicyclists could pass through a gap between the poles and emergency vehicles could clear a concrete block dividing the gap. In all other respects the boulevard functioned as a normal city street, with full access to all residences and on-street parking.

This was the original concept of the bicycle boulevard: a roadway where bicycle traffic has right-of-way priority over intersecting streets, and periodic full-width barriers discourage through motor vehicle traffic. It can be viewed as the exchange of a traffic-calming device unfriendly to bicyclesCSTOP signsCfor another friendly to bicycles (if designed correctly)Ctraffic barriers.

The evaluation of the initial six-month demonstration study reported that bicycle traffic on Bryant Street increased dramatically. High school students constituted a significant portion of the flow. Motor vehicle volumes within the corridor remained fairly constant, indicating that traffic was not diverted to other local streets. Anticipated problems with accidents, access to residences, abusive behavior by bicyclists, and increased moped and motorcycle traffic failed to materialize. The report concluded that "This test of the bicycle boulevard concept has shown that a predominantly stop-free bikeway corridor on a less traveled, local residential street can be an attractive and effective route for bicyclists."

In 1986 the footbridge was replaced by a separate, wider bicycle bridge and an improved pedestrian bridge. In 1990, the original wooden barriers were replaced by permanent raised and landscaped concrete islands. The boulevard was extended by two miles in 1992. Where Bryant Street crosses a major arterial, Embarcadero Road, a new traffic signal was installed. Channelization forces automobile traffic on Bryant Street to turn right at this signal, but allows through bicyclists. The signal is actuated by bicycle traffic through pavement detectors and by pedestrian pushbuttons. (This signal was by far the most controversial element of the extension.)

Beyond the signal, an existing drainage dip serves as sort of an inverted speed hump to slow traffic. Several blocks farther on, a barrier was originally installed, but as a result of neighborhood resistance it has been replaced by a traffic circle. Where Bryant Street continues through downtown Palo Alto it receives no special treatment, except for signs identifying it to bicyclists and motorists as a bicycle boulevard. At the Menlo Park border another creek serves as a deterrent to through traffic; a bicycle bridge crossing this creek is one block away.

Creating Bicycle Priority Streets Through Traffic Calming

Bicycle Boulevards can be created on residential streets on which traditional bicycle facilities, such as bike paths and bike lanes are unsuitable. Bicycle Boulevards confer traffic calming benefits on residents and pedestrians as well as on bicyclists who do not necessarily live in the neighborhood. Many bicyclists now use such residential streets. An example is Page Street in San Francisco. However, their utility is significantly decreased by STOP signs at nearly every intersection. The boulevard does not have to be a single straight route; it might also be a circuitous (but flat) corridor like the Duboce-Steiner-Waller-Scott route otherwise known as the wiggle. In addition, bicycle boulevards are relatively inexpensive to implement.

Bicycle priority streets, as envisioned in this plan, will provide bicyclists simultaneously with three advantages that do not exist in the current street network:

1. A low traffic volume alternative where bicycles and motor vehicles can share the roadway without conflicts; and

2. Significantly reduced travel time since bicyclists on the route are granted the right-of-way at as many intersections as possible. The SFBC has suggested a goal for Bicycle Priority Streets of three out of four consecutive intersections where bicyclists on the route are granted the right-of-way without having to stop for cross traffic. This would be possible by converting four-way STOP signs to two-way stops or switching two-way STOP signs to stop the cross street rather than the designated bicycle priority street. A traffic engineering study must be undertaken at each subject intersection to confirm that safety is not compromised.

3. A route where two or more bicyclists can safely ride side-by-side. This increases the attractiveness of bicycling to families as well as other cyclists who enjoy conversing during their transport just as motorists and pedestrians do.

Traffic calming strategies are needed to prevent the diversion of motor vehicle traffic to the newly prioritized bicycle street. Although the original concept in Palo Alto employed two motor vehicle barriers, the extension showed that forced turn channelization and traffic circles can also work to discourage through auto traffic. Portland has established a bicycle boulevard on Lincoln Street, an important link between Mt. Tabor Park and residential neighborhoods, using traffic circles and barriers. In fact, as this chapter will discuss, a whole arsenal of bicycle-compatible traffic calming measures is available for use on bicycle boulevards. These measures vary considerably in the level of traffic restriction. The selection of specific measures can be tailored to provide exactly the degree of through traffic control needed at the location where each is placed while minimizing interference with important turning movements.

Two conceptual designs are depicted in Figure 6-1, but virtually dozens of design concepts are possible by mixing and matching the above strategies. Figure 6-2 depicts a more aggressive re-design of a residential street whose existing cross-section is a minimum of 42 feet curb-to-curb. The strategies used will depend on whether the goal is to prohibit through non-neighborhood traffic altogether, or merely slow all traffic to bicycle speeds, or slow all traffic to posted speed limits. In other words, traffic calming can create bicycle priority streets which can, in turn, be implemented by either (1) accepting ambient traffic speeds on residential street but ensuring that traffic volumes remain low enough that bikes and cars can share the road, or (2) re-designing a street for a maximum speed of (for example) 15 mph for both bikes and cars.

Traffic calming techniques can also be used to slow traffic to posted speed limits on virtually all San Francisco streets with speed limits of 35 mph or less. In addition, it is recommended that the speed limits of all streets posted greater than 35 mph be reviewed to determine if such speeds are appropriate for the existing conditions, including curb lane width and ability of motor vehicles to safely share the roadway with bicycles.

Like most traffic calming measures, bicycle boulevards may meet opposition from some citizens whose circulation patterns are upset or who resist change of any sort. In addition, the boulevard is seldom as direct or as efficient as an arterial, if one is nearby, and is engineered for lower speeds. Experienced bicyclists who prefer arterials should not be expected to use the bicycle boulevard instead, and improvements to the arterial should not be neglected merely because the bicycle boulevard is present. However, even experienced cyclists may prefer a less stressful commute at times.

Recommended Bicycle Priority Streets

and Other Streets Recommended for Traffic Calming

The corridors that have been identified as providing the most benefit to bicyclists as bicycle priority streets are:

_ Cabrillo Street between La Playa Street and Arguello Boulevard

_ Cayuga Avenue between Still Street and Ottawa Avenue

_ Clay Street between Webster and Cherry Streets

_ Downey Street between Waller and Ashbury Streets

_ Duboce Avenue/Steiner Street/Waller Street/Scott Street (between Market and Page Streets) _ Eureka Street/23rd Street/Diamond Street/Jersey Street/Chattanooga Street/22nd Street (between Market Street and Potrero Avenue)

_ Francisco Street between Lyon Street and Cervantes Boulevard and between Polk and Laguna Streets

_ Greenwich Street between Octavia and Lyon Streets

_ J.F.K. Drive between The Great Highway and Kezar Drive (in Golden Gate Park)

_ Holloway Avenue between Junipero Serra Boulevard and Plymouth Avenue

_ Hugo Street between 7th and 3rd Avenues

_ Kirkham Street between Seventh Avenue and Lower-Great Highway

_ Lake Street/Sacramento Street between 30th Avenue and Cherry Street

_ Pacific Street between Mason and Powell Streets

_ Octavia Street/Green Street between Francisco and Polk Streets

_ Page Street between Stanyan & Market Streets

_ Sacramento Street between Cherry Street and Arguello Boulevard

_ Tiffany Avenue/29th Street/Dolores Street/30th Street/Chenery Street/Diamond Street/ Circular Avenue/Hearst Avenue/Gennessee Street (between Valencia Street and Judson Avenue)

_ Taraval Street/Madrone Avenue/Ulloa Street/16th Avenue between Dewey Boulevard and Vicente Street

_ Vicente Street between Lower Great Highway and 14th Avenue

_ Webster Street between Clay Street and Pacific Avenue

_ 15th Avenue from Lake to Cabrillo Streets

_ 17th Street between Market and Kansas Streets

_ 20th Avenue between Lincoln Way and Wawona Street

_ 21st Avenue between Sloat Boulevard and Ocean Avenue

_ 23rd Avenue between Lake and Fulton Streets

_ 34th Avenue and Clearfield Drive between Lincoln Way and Lake Merced Boulevard

The start and end points for the above recommended streets, at least as far as their bicycle priority status is concerned, are contained in Appendix B-2. This list is not meant to be a comprehensive list of the only candidate streets for traffic calming but rather a list of the streets that have the highest priority for traffic calming due to their importance to bicyclists. It is certain that, as the City embarks on the public participation process necessary to implement these recommendations, other corridors and streets will be identified. These should be added to the Bikeway Master Plan as they are approved. Recommendations for a strategy to begin a traffic calming program in San Francisco are presented in at the end of this chapter.

In addition, there are numerous streets that are important to bicyclists and have high speed traffic, but which for various reasons do not meet the criteria for bicycle priority streets (see next section), and thus would not be suitable for the maximum treatments as illustrated in Figure 6-1. In some cases, the existing posted speed limit would be sufficient if only it were observed. On these streets, the City should take specific steps to reduce travel speeds such as: synchronize lights at slower speeds, reduce curb radii, eliminate free right-turns, require traffic turning right from the street in question onto a side street to STOP or be under signal control, and, of course, increase enforcement. On local streets or streets whose speed limits are 25 mph, other measures can be considered such as speed humps/pavement undulations or traffic circles.

Some streets to consider for a reduction in travel speeds are:


_ Cesar Chavez Street

_ Howard Street

_ Bay Street

_ J.F. Kennedy Drive

_ Broadway

_ Kezar Drive

_ Bryant Street

_ Martin Luther King, Jr. Drive

_ Bush Street

_ Oak Street

_ Fell Street

_ Portola Drive

_ Folsom Street

_ Potrero Avenue

_ Golden Gate Ave. east of Van Ness Ave.

_ San Jose Avenue

_ Guerrero Street

_ Third Street

_ Harrison Street

_ Fifth Street

_ Alemany Boulevard


Criteria for Bicycle Priority Streets

Since a bicycle priority street eliminates most STOP signs for through traffic, measures are usually needed to prevent it from attracting motor vehicles as well as bicycles. Measures may also be needed to prioritize the preferred bicycle movements such as left-turn/right-turn movement along the wiggle. As a rule, the primary goal of traffic calming measures on a bicycle priority street is either access control or speed control. Access control, such as cul-de-saccing a street mid-block, half barriers at intersections or other measures to reduce the amount of non-neighborhood traffic, need be implemented at only a few points, spaced as widely as half a mile apart. Speed control measures are usually effective only in their immediate vicinity.

Streets that are candidates for conversion to bicycle priority streets should meet the following criteria:

* The concept has the support of residents. The implementation process for traffic calming measures should have extensive public involvement as discussed in the Implementation section at the end of this chapter.

* The route should appeal to casual bicyclists by being on streets with low traffic volumes.

* The route should appeal to experienced bicyclists by being as direct and fast as possible by giving priority to bicycle travel over motor vehicles.

* The route should not be a street classified as a major thoroughfare or a transit preferential street. In cases where this situation cannot be avoided, provisions will be made to accommodate bicycles without interfering with the operation of the other primary transportation mode.

* The route should reduce delays to the bicyclist by assigning the right-of-way to travel on the route.

* On low volume streets (less than about 2000 vpd), motor vehicle access should be restricted only enough so that autos are not diverted from other thoroughfares to the bike route. On higher volume streets, the degree of restriction will depend on the character and ability of adjacent streets to accommodate traffic diversion.

* Intersections with major streets are or could be controlled by traffic signals.

* The bicycle boulevard should not be a major commercial destination.

Consistency with the Transportation Element of the Master Plan

Many of the negative effects of automobile traffic are easily apparent in San Francisco and elsewhere in the Bay Area, California, and the United States. The Preliminary Draft of the Transportation Element of the Master Plan (largely unchanged from the existing language), says:

The impact of automobile traffic on the San Francisco environment is an undeniable problem. Increasing traffic causes more environmental damage in addition to greater difficulty and inconvenience in traveling within the city. Efforts to accommodate the automobile in the cityCusing land and resources for off-street parking, constructing freeways, designating streets for greater traffic volumesCthreaten the attractive appearance and economic viability of the city's neighborhoods. A basic assumption of the Transportation Element is that a desirable living environment and a prosperous business environment cannot be maintained if traffic levels continue to increase. Various methods must be used to reshape the impact of automobiles on the city, including improving and promoting public transit and ridesharing as an alternative to the single-occupant automobile; limiting the city's parking capacity, especially long-term parking in commercial areas; directing major traffic movements to certain routes; limiting the vehicular capacity of the city's streets and highways; and accepting a certain level of congestion in the city as inevitable. . .

Clean air, minimal traffic congestion, a wide array of transportation alternatives and a human-scaled, pedestrian-oriented urban environment attract both residents and businesses. On the other hand, the costs of pollution, congestion, and automobile-oriented development of a scale that is unpleasant and inconvenient for pedestrians are not only measured in urban flight and loss of business, but also in the penalties that may be assessed by local governmental agencies such as the Air Quality District when the blighted conditions are not brought into compliance with established standards.

In 1973 the Board of Supervisors adopted the "Transit First Policy," giving priority to transit investments and adopting street capacity and parking policies to encourage increases in automobile traffic.

Adopting the concept of Bicycle Preferential Streets would be consistent with the Master Plan and with the past action of the Board to encourage transportation alternatives to the automobile.

The selection of an existing low volume street is compatible with both the objectives for bicycle priority streets and the objectives of the Master Plan for local residential streets because:

* Implementation would result in little or no potential to divert traffic to other residential streets;

* No bike lane striping is required to separate bikes from cars; and

* Intersection controls can be modified without increasing delay congestion at critical intersections.

The next section discusses in detail the most beneficial traffic calming measures for this purpose.


Since bicyclists are permitted on all roadways except designated freeways, and therefore everywhere that traffic calming might be used, traffic calming measures should always, at a minimum, be safe for bicyclists. This section discusses traffic calming measures that are safe and can also be used effectively to bicyclists' benefit, for instance, on bicycle boulevards. Other measures that are incompatible with or potentially harmful to bicyclists, or neither helpful nor harmful, are described in Appendix E, "Non-Bicycle Oriented Traffic Calming Measures".

Most of these measures employ physical design features that guide or restrict the movement of vehicles. A few are traffic control devices, including signs, signals, and striping that communicate regulatory, warning, or advisory messages. Design features are usually self-enforcing and are also the most successful designs because police enforcement is usually a short-term service whose benefits end when the police leave. Thus self-enforcing designs are preferred over other designs. However, traffic control devices do not necessarily change driving habits and there may need to be an initial period of education and/or police enforcement for maximum success.

Many traffic calming measures serve more than one purpose. Traffic circles, for instance, both narrow the roadway and force a change in direction. It is also common for installations to implement several measures in combination.

In some cases, it is advantageous to treat bicycle traffic differently from automobile traffic for traffic calming purposes. There are several good reasons for doing this:

* Most residents do not consider bicycle traffic on their streets a nuisance or hazard in the same way as they do automobiles.

* Many bicyclists prefer to ride on streets where automobile traffic is light, such as those that have been traffic-calmed.

* Many cities, including San Francisco, would like to actively promote bicycle travel as an environmentally sound method of transportation.

The following discussion identifies methods for calming motor vehicle traffic that are compatible with bicycling.

Changes in Elevation

Speed Humps - Speed humps, also called pavement undulations or road bumps, are raised areas extending across the pavement surface, typically 3 to 4 inches high and 12 feet long in the direction of traffic flow. They must be carefully distinguished from the high, narrow speed bumps sometimes used in private parking lots and driveways, which traffic engineers do not recommend on city streets. Speed humps are very common in California cities.

Speed humps are meant to cause discomfort to occupants of vehicles that exceed the design speed, and are usually installed in a series of two or more. Improperly designed, speed humps and all speed bumps are dangerous for bicyclists. They can damage the wheels or frame, or it can knock the bicyclist down. Conventional narrow speed bumps, for instance, are known to have caused at least one bicyclist death, and every speed bump design that has been tried is dangerous for some class of vehicles.

Fortunately, properly designed speed humps, with gentle approach and exit gradients, flush leading edges, and smooth surfaces, do not seem to pose a significant hazard to bicyclists. British government research found that 92 percent of users of two-wheeled vehicles had no trouble crossing 0.1-meter (4-inch) humps. The California Traffic Control Devices Committee's Subcommittee Report on Pavement Undulations found that bicyclists may experience loss of control at speeds approaching 20 mph for a 4-inch hump, or 25 mph for a 3-inch hump. The report found no problem at speeds of 15 mph or less.

With one exceptionChillsCbicyclists are unlikely to exceed 25 mph on residential streets, and few will exceed 20 mph. Thus, both 3-inch and 4-inch humps are likely to be safe for bicyclists, although the 4-inch hump should probably be used with caution where bicycle traffic is frequent or rapid. Humps can be tapered near the curb or have cuts in them to allow bicyclists to bypass them, although this practice is not strictly necessary and can encourage gutter-running (driving with one wheel in the gutter) by motorists. It is also important to ensure adequate warning signs and markings. The exception to these bicyclist speeds is on hills. (The death referred to above occurred on a steep hill.) Bicyclists who inadvertently approach a hump at high speed might risk serious injury. It is also possible that a hump could cause a slow bicyclist to lose control on a steep uphill grade. The City of Oakland will install speed humps only on residential streets and only on streets with grades less than 5 percent.

Speed humps are normally used only on local streetsCusually residential streets, although Portland has tested a 22-foot long speed hump for use on collector streets. Since 1988 the City of Palo Alto has experimented with 3-inch high humps on several residential streets. The humps do not appear to impede or pose a hazard to bicycle travel. It should be noted that in many jurisdictions, departments that operate emergency and transit vehicles oppose speed humps at least on collector streets.

Speed humps should be located far enough from intersections that turning cyclists are no longer leaning when they encounter the hump. Finally, maintenance should ensure that raveling of the hump's edge does not produce irregularities, gaps, or debris that could impede or endanger bicyclists.

Speed Tables - A flat-topped hump is called a speed table; its length in the direction of travel can be much greater than that of a conventional hump. Speed tables, usually distinctively paved, are often used at pedestrian crosswalks, where they must extend curb to curb and no cyclist bypass is possible. Otherwise, considerations for speed tables are the same as those for speed humps and for textured surfaces.

Raised Intersections - A raised intersection is similar to a speed table, but extends across the full width of an intersection on all four approaches. Raised intersections have been used extensively in Europe for residential traffic management, and occasionally in the United States in shopping areas. As with speed humps and tables, the approach and exit gradients should be gentle, and the surface should be smooth but not slippery.

Roadway Narrowing

Lane Narrowing - Restriping of roadways to provide fewer lanes, or narrower lanes, can create enough room for a bicycle lane or a curb lane wide enough for bicyclists and motorists to share comfortably. For instance, Seattle has restriped some streets from four lanes to two plus a two-way left turn lane and bicycle lanes. At the same time, fewer lanes or narrower lanes may tend to reduce vehicle speeds. Such modifications can be viewed either as the roadway being restriped to accommodate bicycles, or as bicycle lanes being used as a means to calm traffic. However, narrowing lanes such that bicycles and motor vehicles are forced to share a lane less than 14 feet wide is not bicycle compatible and should not be considered.

Traffic Circles - Small traffic circles, also called mini-roundabouts or speed control islands, have been used with great success in Seattle's Neighborhood Traffic Control Program, where they are installed at the request of citizens. Located at the center of an intersection in place of STOP signs or traffic lights, traffic circles both narrow the roadway and force motorists to change direction. They may also produce the visual impression of a dead-end street, at least to strangers.

Although traffic circles seem relatively benign, recent trial installations in the Willows neighborhood of Menlo Park have produced heated controversy among residents. A letter to the editor in opposition to them cites traffic diverted to other neighborhood streets, reduced emergency vehicle response times, traffic hazards, "reduced property values due to the slumlike visual connotations of the obstacles," and the cost of the circles themselves.

The bicyclist's objection to all these means of narrowing the roadway is the same. Unless the narrowing is substantial and frequent, any reduction in vehicle speed is usually small. At the same time, the narrow lanes tend to squeeze motorists and bicyclists together. To avoid this conflict, the roadway should remain wide enough for lane-sharingCabout 12 feet or wider, depending on traffic volume; otherwise additional traffic calming techniques should be used along with the narrowing, or a cyclist bypass should be provided if geometry permits.

Of all the roadway-narrowing measures, small traffic circles seem to be the most comfortable for bicyclists. This may be because they inherently combine several traffic-calming techniques; because they do not create a competition for the remaining space; or because they are often used on roadways that already carry relatively little traffic. In addition, the elimination of STOP signs that they make possible is highly beneficial to bicyclists. They are not, however, free of controversy. Some bicyclists object to the complication and confusion of turning and crossing movements, the decreased clearance between bicyclists and cross traffic, and the danger of left-turning motorists who shortcut the circle clockwise to avoid traveling counterclockwise three quarters of the way around it. In addition, bicyclists would be better served by stopping the side street traffic to give travel on the street in question the right-of-way. This is especially true if the side street has significant traffic volumes.

A well-designed traffic circle employs a small size and sharp deflection at entry to force entering traffic to slow drastically and to continue slowly around the circle. A small triangular island at the entry can force a right turn, eliminating shortcuts, and also provides a pedestrian refuge.

Changes of Direction

Reduced Corner Radii - Reducing the corner radius at intersections to as little as 7 feet both slows down the speed of turning traffic and reduces the distance pedestrians must cross. It is an effective technique in high-pedestrian areas, and can also be used to reduce the speed of traffic entering the cross street. However, large trucks may not be able to negotiate the turn without overrunning the curb.

This technique can also be applied on arterials, although the geometry is largerCreducing corner radii from 50 feet to 30 feet at freeway on-/off-ramps, for example.

Restricted Movements

Road Closures/Traffic Barriers - As used here, "road closure" refers to closing a road at one point, either at an intersection (creating a cul-de-sac) or midblock (creating two cul-de-sacs). It does not mean closing an extended portion to vehicular traffic, as authorized by Vehicle Code '21101(a), which might be done to create a pedestrian area. In Europe, such a point closure is called an "environmental" road closure. The closure is usually accomplished by installing a barrier, whose design can vary from an asphalt berm to a set of posts or bollards to a sculptured and landscaped island to a full cul-de-sac with curb and gutter. These designs differ in cost, appearance, and ease of maintenance but not in basic functionality.

Traffic barriers are sometimes called diverters, since when traffic is blocked from one street it does not usually disappear, but is instead diverted to another nearby street. This chapter uses the term "barrier" for a device that blocks movement completely, and reserves "diverter" for a device that restricts some movements, usually the through movement, but allows other traffic to continue. Many Bay Area cities have installed traffic barriers, notably Berkeley and Palo Alto, to prevent commute traffic from cutting through neighborhoods. Barriers are the most extreme traffic calming measure, and are, of course, highly successful in reducing traffic volume and speed near the installation point. Barriers also tend to be highly controversial and are unpopular with a some citizens since they restrict access for residents and visitors as well as outsiders.

Barriers can create two kinds of problems for bicyclists:

* They do not always allow easy bicycle passage. (In the case of barriers constructed of guardrail, like some in Berkeley, they may not allow passage at all.) This is primarily a matter of barrier design. If the barriers are constructed with bicyclists in mind, they can continue to allow unrestricted bicycle access.

* Because motorists look in directions where they expect to see other motorists, they fail to anticipate bicyclists who suddenly enter an intersection across or through a barrier. This problem is primarily a matter of barrier placement. It can be avoided with proper placement and with notification to either bicyclists or motorists that they must yield.

In order to prevent these potential problems as well as potential neighborhood opposition, exceptional attention must be paid to the selection of a location for barriers as well as the details of the design and placement.

Barrier Design - Every barrier should have a gap or opening to allow bicycle passage. To allow for trailers and adult tricycles, the gap should provide a clear width of at least 5 feet (Highway Design Manual, Topic 1003.1), although as little as 4 feet can be workable. The practical maximum is 5 feet 6 inches, set by the width of an automobile. On a two-way street this clear width should be provided for each direction of bicycle travel, either by two separate approximately 5-foot openings or a single approximately 10-foot opening in the center, divided by a concrete block or a 4-inch diameter, 4-foot high locking barrier post. The single opening has the advantage that it can allow passage of emergency vehicles.

In some cases it may be necessary to prohibit parking near the barriers by means of signs or red curbs to preserve access to the openings. The exact location of the openings between the center of the road and the curb is not usually critical as long as the guidelines below for placement of the barrier itself are followed.

The barrier itself should be liberally identified, as appropriate, with single white or yellow reflectors, diagonal reflector arrays, edge reflectors, and reflective tape or paint. The upper half of posts should be wrapped diagonally with parallel stripes of orange and white reflective tape for maximum visibility day and night, and a 2-by-10-foot envelope should be painted on the pavement around the post.

Plantings on landscaped barriers or closures should not obstruct sight lines, and should minimize the shedding of leaves, seeds, fruit, or nuts onto the roadway.

Barrier Placement - The relevant principle is that on the far side of a barrier, bicyclists should not immediately encounter cross traffic at intersections or driveways. This means that full barriers should not be placed directly at intersections, but set back at least 50 feet from any cross street or business driveway. (Fifty feet is a reasonable stopping distance, including reaction time, for a bicyclist traveling at 15 mph.) With some designs and at some locations, it may be necessary to prohibit on-street parking or to trim foliage to provide adequate sight lines.

This placement also ensures that bicyclists who are leaning to turn onto a street with a barrier have a chance to return to an upright position by the time they encounter the barrier, and therefore to pass through the barrier safely.

Half Closures - The road is closed at one point by a barrier but only across half its width. This is almost always done at the street entrance, allowing traffic to exit but blocking it from entering and creating a de facto one-way street for one block (except for traffic that originates within the block). Where the half closure includes a bypass for bicycles to enter, the result resembles a contraflow bike lane without that design's inherent disadvantages.

The same design considerations for bicycles apply to half closures as to full closures, although a half-width barrier needs only one opening. The preferred location at a street entrance is satisfactory, since there is no conflict with cross traffic on the far side of the barrier.

Half closures have the advantage of greater flexibility in placement than full closures. Although they can be physically violated by motorists fairly easily, the rate of violation should still be relatively low since motorists must consciously decide for example to enter a one-way opening. By the same token they offer easy passage to emergency vehicles. The security of half closures can be improved by extending a concrete median beyond the barrier (provided that it does not block access to driveways or parking, and even this can be provided to some extent by openings), forcing drivers to travel on the wrong side of the road for prolonged distances in order to circumvent the barrier.

Diagonal Diverters - A diagonal diverter is a barrier placed diagonally across the full width of an intersection, creating two L-shaped streets touching but not connected at the corners. Again, Berkeley is the prime example in the Bay Area of the use of the diagonal diverter although its use of them is not particularly bicycle friendly. Diagonal diverters are also used in Eugene and Seattle.

Diverters may be less objectionable to motorists than barriers, but they can be unsatisfactory to through bicyclists, who (depending on the diverter geometry and bicyclist maneuver) may be exposed to unsuspecting cross traffic on both sides of the diverter. Since they function only in intersections, there is no flexibility in diverter placement. The design should therefore provide an opening that is both wide enough for passage and long enough in the direction of travel to create a refuge: 6 feet for a bicycle, or 10 feet for a bicycle plus trailer. This length can most easily be provided if the diverter is constructed as a tapered island or as a permanent landscaped closure, although it can also be created by a double row of bollards.

Since the purpose of the diagonal diverter would be to track most of the traffic into a forced right- or left-turn, such as at Steiner/Waller, it is suggested that the bicycles allowed through the diverter be required to yield to on-coming traffic on the other side, be it motor vehicle or bicycle.

Figure 6-3 shows several variations of diagonal diverters and alternatives to diagonal diverters that can prioritize the left-turn/right-turn movements needed to execute the Duboce Wiggle.

Truncated Diagonal Diverters - As used in Seattle, one end of the diagonal diverter does not extend fully to the corner, permitting right turns as well as left turns on one of the four streets, while continuing to prevent all through movements. It would be possible to vary the design even further to widen this gap, permitting left turns as well as right turns on the intersecting street, or to provide gaps at both ends, creating a kind of diagonal median barrier. These may need to be used in conjunction with STOP signs to assign right-of-way to certain movements.

Median Barriers - Median barriers are currently used in virtually every city on major arterials where they separate opposing directions of traffic and prevent left turns to and from minor streets. For traffic management purposes, short median barriers can also be placed at intersections to prevent through movements. These barriers differ from the median islands discussed above under "Roadway Narrowing". Median islands are placed along the traffic-calmed street to narrow it, while median barriers are placed perpendicular to it along the centerline of the cross street to prevent traffic from entering or continuing. (A single barrier can serve both purposes on intersecting streets.)

The usual median barrier permits right turns and prevents left turns, but design modifications can add one or two of the four possible left turns according to need.

To suit bicyclists' needs, the barrier must have a bicycle bypass (or two, depending on design). If it crosses a busy uncontrolled intersection, it is best designed as an island that includes a bicycle refuge.

Forced Turns - Traffic can be forced to turn right rather than continue straight by a pork-chop shaped island, similar to the familiar type used for free-running right turns, but extending further to the left to block through travel. It is easy to incorporate a bicyclist bypass around or through the island. With some geometries it might be possible to force left turns as wellCfor instance, offset intersections, turns from one-way streets, and turns from the right arm of a T intersection.

Unlike diagonal diverters and median barriers, this method leaves the interior of the intersection clear. The right-hand curb radius may need to be increased to accommodate the forced turn, and large trucks may not be able to negotiate it.

Signs and Markings

Coordinated Traffic Lights - This strategy is usually thought of as facilitating traffic flow not calming it. It is usually employed to enable traffic to travel at a higher average speed than it could without coordination. But coordinated traffic signal timing also removes any advantage for motor vehicles to travel faster than the speed for which the traffic signals are timed. Of particular relevance to bicyclists is that a signalized arterial could be coordinated for bicycle speeds rather than motor vehicle speeds. This has been done in Portland, where downtown streets are timed at 14 mph. This can be done in San Francisco to reinforce lower speed limits or existing speed limits after careful consideration of delay, air quality and diversionary impacts. Air quality impacts should be minimal assuming motorists will quickly learn the optimal travel speed to avoid excessive idling. Supplemental signing posting the speed for which the signals are timed would shorten the learning curve.

Changes in Surface

Irregular or Textured Surfaces - Brickwork or pavers of various colors, shapes and patterns can be used to set off a crosswalk, the entrance to a pedestrian area, or the entire area itself. The warning is primarily visual, although motorists may notice mild noise or vibration. For bicycle safety, the surface should be free of steps, longitudinal or diagonal grooves, or other irregularities that could cause a fall, should not be slippery or become so when wet, and should not be so rough that it causes an uncomfortable ride. These concerns are not a problem with some common designs. Any proposed use of such textured pavements done in consultation with the Bicycle Coordinator and the BAC.

Summary of Bicycle-Compatible Measures

Assuming that the design guidelines just described are observed, the most bicycle-compatible traffic calming measures are the following:

* Speed humps, speed tables, and raised intersections can produce small but consistent speed and volume reductions, but only in their immediate vicinity.

* Traffic circles are acceptable on streets whose volume is already fairly low, and moderately effective in reducing both speed and volume.

* Reduced corner radii can slow the speed of turning traffic. They are most likely to be useful on a bicycle priority street in combination with other measures that operate midblock. But they can also be useful in making junctions with on- and off-ramps safer for bicyclists. The elimination of right-turn channelization pork chop islands would also slow turning traffic if the curb radii were also reduced.

* Road closures (traffic barriers) are the most coercive and therefore most effective of all traffic calming measures.

* Half closures are less intrusive, offer greater flexibility in placement, and allow emergency vehicles to pass.

* Forced turn channelization can be highly effective if existing geometry permits it to be used, and is less coercive than road closures. It is a good substitute for diagonal diverters.

* Median barriers, like half closures and forced turns, prevent through vehicular movements but can be configured to permit other movements. If there is significant uncontrolled cross traffic, the median can include a bicycle refuge.

* Traffic signals in downtown core areas (i.e. with signals every block) can be coordinated for a speed suitable to bicycle travel, e.g. 10 to 20 mph.

* Textured surfaces have little effect by themselves, and would be most useful as a visual cue to reinforce more restrictive design features.


The legal authority for many traffic calming measures is Vehicle Code '21101(f), permitting local authorities to prohibit entry to or exit from any street by means of islands, curbs, traffic barriers, or other roadway design features. Traffic control devices or markings placed on the barriers must conform to the uniform standards and specifications of '21400. There are two ways of permitting bicyclists to pass through road closures, diverters, forced turns, or median barriers on a bicycle boulevard (or elsewhere) while preventing motorists from doing so:

* The barrier to passage is a purely physical one. There is no legal prohibition against crossing the barrier, but its design simply allows bicycles while interfering with motor vehicles - for instance, an opening wide enough for bicycles but too narrow for automobiles. With this approach, warning signs such as W3 (turn arrow), W57 (single head arrow), W53 (Not a Through Street), W81 (chevrons), and many others would be permissible, but regulatory signs such as R11 (Do Not Enter) would not. There is no practical way to exclude motorcycles, mopeds, or motorized bicycles.

* A regulatory sign prohibits passageCfor example, R11 (Do Not Enter) or R41 (Right Turn Only)Cand violating it has legal consequences. In this case there must be an exception for bicycles. Palo Alto sometimes installs an "Except Bicycles" plate on signs of this sort at barriers, but such a distinction is not specifically permitted under state law.

Both approaches run into difficulties with '21101.6, which prohibits local authorities from placing "gates or other selective devices on any street which deny or restrict the access of certain members of the public to the street, while permitting others unrestricted access to the street." Although intended to codify a court decision prohibiting key-operated gates open only to residents, and to prevent discrimination based on drivers (rather than on vehicles), this section nonetheless poses a significant obstacle to selective regulation of motor vehicles at traffic barriers. This issue, and proposed amendments to state law to deal with it, are discussed at greater length in Chapter 8.

Local authorities are permitted to regulate turning movements at intersections by placing signs or other traffic control devices, and it is unlawful for vehicular traffic to disobey these signs ('22101). Again, there is no explicit provision for distinguishing bicycles.

Conceivably, a short section through a barrier could be designated as a bicycle path (if it were at least 5-foot wide for one-way travel, as required by Caltrans standards), legitimizing the distinction between bicycles and motor vehicles.



The purpose of this section is to recommend an appropriate approach for the successful implementation of community based traffic calming measures. This segment of the Plan begins by reviewing the current community involvement measures that exist in San Francisco. Next, the requirements of various traffic calming measures will be discussed. Key elements of the approaches that have been used in other cities are also reviewed. Based on the relative successes that have been achieved by other implementation programs, similar characteristics currently present in San Francisco are discussed. Finally, a step by step approach is recommended for the implementation of future traffic calming measures.

Current Community Involvement Efforts

The City of San Francisco has not had an aggressive community outreach effort to support the implementation of various traffic calming measures that might advance the goal of greater bicycle usage.

The major bicycle related community outreach effort that has been pursued by the City of San Francisco is the "San Francisco Bicycle Facility Improvement Program" or "Spot Improvement Program". This program provides return postage paid improvement request forms in shops and locations frequented by bicyclists. The program is designed to provide low cost improvements suggested by concerned cyclists such as signage, pavement striping, rack installation, and pavement maintenance. The program has been successful. However, it is not the type of outreach program that supports a significant traffic calming effort that might serve an entire neighborhood.

In addition to this program, the City established the Bicycle Advisory Committee (BAC). The BAC has successfully recommended commuter bicycle routes, reviewed plans for the Presidio and Golden Gate Park, and assisted in the review of the on-going planning efforts associated with this plan. However, this committee has not yet initiated an outreach program specifically designed to implement and encourage traffic calming measures within the City.

Approaches Used by Other Cities

The key element that characterizes successful traffic calming programs in other cities is a high level of citizen participation. "Grassroots initiatives" have successfully brought about significant traffic calming programs in Portland and Eugene, Oregon; Seattle, Washington; Palo Alto and Davis, California; and New York. The major elements common to these programs are as follows:

* Organized Citizen Groups - Each of these cities had volunteer citizen groups that either orchestrated or contributed to the development and implementation of a strong traffic calming program. The "Auto Free New York Coalition" began the work in New York that brought about the Greenwich Village Traffic Calming Study. The very successful traffic calming program that is currently being implemented in Portland was aided by two strong citizen groups: the Bicycle Transportation Alliance and the Willamette Pedestrian Coalition. Many bicycle programs are often inhibited, stalled, or suspended due to changes in pubic transportation agency staff and funding cutbacks. The existence of a strong citizens group can help maintain a consistent policy approach and influence the allocation of additional public resources for bicycle facilities.

* Established Goals and Specific Objectives - Successful programs had specific objectives that were endorsed and incorporated into various city agency planning documents. For example, the City of Portland established a goal in the 2040 Plan for a 5 percent bicycle mode split for commuter work trips. The New York City Transportation Commissioner approved a policy in June, 1991 that would increase bicycle usage by 25 percent by the year 1995. Because this goal was endorsed at the City's commission level, it applied to numerous departments, not just the sole City agency for which the Bicycle Coordinator position works.

* Specific Procedures for Traffic Calming Implementation - In those cities with successful traffic calming programs, there were specific steps that individuals and neighborhood groups could utilize to obtain funding for their programs. In some cases these steps involved surveys of the impacted neighborhoods, in others neighborhood petitions were accepted by City officials. If funds were not available for particular traffic calming measures that budget year, a short range capital programming document incorporated those improvements in subsequent years.

Selected Elements Appropriate to San Francisco

The City of San Francisco currently has two citizen groups that are actively involved in promoting improvements in bicycle facilities and usage. The San Francisco Bicycle Coalition (SFBC) and the City's Bicycle Advisory Committee (BAC) are established organizations that can be very useful in promoting traffic calming measures.

In addition, the development of the Comprehensive Bicycle Plan provides an opportunity for the establishment of specific goals to increase bicycle usage within the City. These goals and objectives are being incorporated into the Transportation Element of the City and County Master Plan, which is currently being revised. If approved by the Planning Commission and the Board of Supervisors, they would become citywide goals and objectives, as well.

However, with the exception of the "San Francisco Bicycle Facility Improvement Program", there are no specific procedures that a neighborhood group could follow in pursuing the implementation of a traffic calming program for their neighborhood, other than letters to City departments and presentations to the Board of Supervisors or selected commissions.

Recommended Implementation Steps for Traffic Calming

in San Francisco

The following traffic calming implementation process is based upon some of the more successful approaches that have been used in the cities mentioned earlier. This particular list of actions is designed to elicit as much information as possible early in the process such that if a neighborhood is not totally behind traffic calming recommendations, efforts can be halted without an excessive outlay of public funds. This recommended step by step procedure draws heavily on the experiences of Seattle and Portland bicycle planners.

Step 1: Community Outreach - Following the completion of the Comprehensive San Francisco Bicycle Plan, the Bicycle Coordinator's Office will distribute the results of the Plan, i.e. route maps and proposed projects, to neighborhood groups and bicycle enthusiasts. In addition, the process for requesting consideration as a future site for traffic calming improvements will be included, i.e. this process. This distribution could possibly be aided by the use of advertising material and/or combination mailings with other public agencies.

The City should employ the services of established citizen's groups to develop community support on a grass roots level to interest neighborhood groups in requesting consideration for traffic calming improvements. For example, providing grant funding to such groups would be a cost-effective way to extend staff resources to educate the public about the benefits of traffic calming and solicit public input on the specific strategies that would/could be employed in the neighborhood.

Step 2: Project Request - The Coordinator's office will be designated as the recipient of the first request for consideration as a potential site for a traffic calming improvement, or a larger request to consider analysis of the entire neighborhood's needs. The Coordinator's office will review the consistency of this request with other existing and proposed City plans, i.e. the Transportation Element, Transit Preferential Streets Program, Emergency Preparedness Plan, and the Pedestrian Streets Program.

Step 3: Preliminary Review - The Coordinator's office will prepare a checklist that summarizes the potential advantages and conflicts of the request. The Coordinator will present the results of this preliminary review to two standing committees that will review these requests on a quarterly basis: the Bicycle Advisory Committee and the newly established Bicycle Plan Implementation Technical Advisory Committee. This new committee should be composed of selected San Francisco public agency representatives that can contribute to this evaluation and implementation. Suggested representatives would come from the Department of Parking and Traffic (DPT), the Department of Public Works (DPW), the Public Transportation Commission (PTC), the San Francisco County Transportation Authority (SFCTA), the Recreation and Parks Department, MUNI, the Police Department and the Department of City Planning.

These two committees will either accept or reject the Coordinator's initial screening of the proposed traffic calming request. If an individual or neighborhood association is denied further consideration by both of these committees and the Coordinator's office, they will have the opportunity to present their proposals to the Parking and Traffic Commission. The Commission will have the final say as to whether the proposed request/project receives further consideration.

Step 4: Priority Rankings - Project requests are ranked on an annual basis. The project rankings are based on the checklist of project advantages and disadvantages that were established by the Coordinator's office in the previous step. The number of project requests that are ranked highly will depend upon the number of requests that are received that year and the funds available for the program.

Project rankings are generally based upon how the project will impact the following concerns:

i. Does the project reduce traffic volumes, and if so, to what level?

ii. Does the project reduce speeds?

iii. Does the project reduce accidents?

iv. Does the project encourage alternative transportation modes, i.e. bicycle and walking?

v. Does the project impact a school setting where increased vehicular safety is required?

vi. Does the project impact other uses that have high requirements for pedestrian or bike access, such as senior housing, park facilities, or youth centers?

vii. Does the project correspond with a designated bike diversion or pedestrian route?

viii. Does the project have low traffic diversion impact on surrounding streets in the neighborhood?

If a project receives a low ranking for more than 3 or 4 years, it is automatically dropped from the program, following a notification to the individual or neighborhood that originally requested the project. The original petitioner can, of course, appeal this elimination to the Commission, or resubmit the project at a later time.

Step 5: Survey to Proceed - Given that a project has received a high ranking and funds are available to implement the project, a brief postcard survey is prepared and distributed to the impacted neighborhood. This survey is designed to evaluate the level of support that the project has within the community, before significant planning or engineering work is begun.

This postcard survey is mailed to each household, business and nonresident property owner within the impacted neighborhood. For the City of Portland, the impacted area was defined as those properties fronting on the affected segments of the project street. When a project only impacted one intersection, the survey would be sent to all properties within a one block radius of the intersection. However, it should be noted that if the project causes significant traffic diversion, then the streets parallel to the traffic calmed street could also be negatively affected by increased traffic and should also be surveyed.

To defer the costs of this survey, Portland requires that the original petitioner be responsible for circulating the survey. If a majority of the impacted properties support the project, the request then moves to the next step.

Step 6: Public Meeting - Using the same mailing list that was utilized in the survey, and expanding upon it to include the full neighborhood, other interested parties, city bureaus, etc. a public meeting notice is then distributed. The purpose of this first public meeting is to inform the public of the project and to solicit input as to potential alternatives or revisions to the project.

Step 7: Establish Project Citizens Committee - Depending upon the size of the project, rather than holding a series of large public meetings, a volunteer citizens committee, that agrees to meet for a few months as the project is defined, is established. This limits the cost of notifications for a public meeting, although the time and place of the citizens's meetings are still carried in neighborhood publications.

The purpose of this citizen's committee is to work closely with staff to define the project. Specifically the group will:

a) Assess the problems and needs to be addressed by this project;

b) Identify project goals and objectives;

c) Identify evaluation criteria that will be used to review the success of the project;

d) Develop alternative approaches/plans/ costs for the proposed project; and

e) Select the final recommendation.

Step 8: Project Development - Working with the citizen's committee, DPT/DPW staff will finalize the project's design and implementation schedule. Cost estimates will be prepared. Following the completion of this work, a final public meeting will be held. Issues associated with any necessary enforcement or education efforts required for the project's successful implementation will be addressed.

Lastly, this step will determine if the citizen's committee wishes to conduct a demonstration project prior to final engineering and full construction of the project.

Step 9: Demonstration Project - A demonstration project should be conducted to determine the impact of the project prior to incurring the costs for full construction. For example, rather than construct a full concrete traffic circle, barriers could be used for a specified period of time.

Within the City of Portland, a second petition is circulated within the impacted area to determine if a demonstration project should be conducted. Again, the original petitioner is responsible for collecting signatures for the demonstration petition. If a majority of the impacted area's properties do not support the demonstration, the project is stopped at this point.

Demonstration projects normally last for approximately 3 to 4 months. This allows the City's engineering staff to review any potential problems that might arise from the project. In many cases a temporary demonstration project is not required, for example street signage or striping. In such cases the costs would be the same whether the improvement was temporary or permanent; this step is therefore omitted for those particular projects.

Step 10: Project Evaluation - As mentioned earlier the citizens committee was responsible for determining what constituted a successful project. The development of evaluation criteria has proven to be a very successful tool in assessing the future use of a particular traffic calming measure and to determine if a proposed improvement should be uniformly implemented throughout the entire neighborhood.

Evaluation criteria are usually based on reductions in the number of vehicles passing a particular point, or counts as to the increase in bicycle usage. Reductions in both auto and bicycle accidents is also a potential criteria. Measurement of before and after speeds/volumes and the impacts on emergency vehicle access is also analyzed.

Following the operation of the traffic calming measures for the selected demonstration time period, the evaluation criteria are applied. Results of this evaluation are reviewed with the citizens committee, property owners and appropriate city departments.

At this point the City is responsible for deciding whether the project should move into final design and construction.

Step 11: Confidential Ballot - Following a successful evaluation, the City of Portland's procedures require a confidential ballot, which the City administers. Although this step could be eliminated based on the scale of the project, Portland has found it a useful tool in determining the neighborhood's support of a project prior to moving into final design and construction.

Step 12: Final Design, Construction, Implementation and Monitoring - The next steps of the project should result in the construction and implementation of the project in a fairly short time period. Because these previous efforts have included such a high level of citizen involvement and participation, the project should be implemented within a fairly short time period. This is particularly true in light of the fact that key property owners could change over a long implementation period and new property owners might request that the entire effort be repeated. Most traffic calming measures within the Seattle and Portland programs are completed within one year.

Project monitoring, however, is a process that goes on for 3 to 5 years. For the City of San Francisco, it would be appropriate for DPT to continue to monitor a project and distribute their findings at the Technical Advisory Committee meetings that were proposed early in this recommended list of steps.

Miscellaneous Recommendations

This recommended step-by-step community based process for implementing traffic calming measures assumes that a number of other factors are in place to support these efforts. Issues that are of particular importance to the City of San Francisco include the following:

Adequate Budget - This program assumes that once a project is highly ranked and the process of surveying the neighborhood and conducting public meetings has begun, adequate budget exists to implement at least the most highly ranked projects. The neighborhood representatives would very quickly lose interest if, after extensive community involvement, the program was not funded for that year. Therefore, to really ensure that this effort is viable, it might be appropriate to begin only after several years of capital funding was established.

Adequate Staff - The level of effort required to initiate and maintain such a program requires more than one full time Bicycle Coordinator. The City of Portland currently maintains a staff of two full time bicycle planners and Seattle has five full time positions.

Multi-Departmental Cooperation - The proposed technical advisory committee is only one element of the multi-departmental cooperation that would be required for this effort. Not only would there have to be a willingness to provide staff support and review for new projects, but other departments would also be involved with on-going monitoring and evaluation of the projects.

Grass Roots Citizen Support - The proposed recommendations have no chance for success unless there is support from the neighborhoods. To initiate this support many bicycle groups have become involved in their neighborhood groups and formed the nucleus for many of these grass roots traffic calming requests. The San Francisco Bicycle Coalition's current goal of increasing membership by 150 percent is well timed to support these efforts.

In summary, all of these elements should be in place prior to the initiation of an aggressive bicycle oriented traffic calming program. However, as other cities have shown, the benefits from such an effort can be significant, further increasing both the quality and safety of urban living.


. Thus, traffic calming can also be used to benefit bicyclists (and pedestrians) by incorporating design features on most or all city streets that discourage automobiles from travelling over 30 mph.

s and barriers, pedestrianized streets and alleys, and erected brick and metal gateways. One large neighborhood was divided into eleven mini-neighborhoods, each physically separated from the rest and accessible only from peripheral arterials. The smaller neighborhoods were intended to enhance the sense of community and discourage outsiders, including those with criminal intent, from wandering undetected into the area. Traffic in the Five Oaks area declined by 67 percent, total crimes by 26 percent, and violent crimes by half; remarkably, crime in other areas not did increase. Newman is currently developing a plan for Seattle neighborhoods, and Richmond, CA has also considered adopting his ideas.

. () See Appendix E for a discussion of the disadvantages of STOP signs to bicyclists.

) () Otherwise known as the wiggle.

: () It should be noted that some of these streets have speed limits justified by a traffic-engineering survey.