Bicycle Safety Guide and Countermeasure Selection System


Building on Success: Road Diet, Streetscaping, and Signal Improvements for Bicyclists on Valencia Street

San Francisco, California

Prepared by Michael Sallaberry P.E., San Francisco Municipal Transportation Agency;
2014 updates by Jill Mead, UNC Highway Safety Research Center


The City and County of San Francisco has the goal to encourage bicycling as a viable transportation option, so city staff are constantly trying to find and create opportunities for the installation and improvement of bicycle facilities. However, with a population of about 780,000 people in a 47-square-mile space, San Francisco is a very dense and congested city where a variety of mode users compete for limited street space. While this reality is one reason that bicycling is a popular way to travel through the city, it also complicates the installation of bicycle facilities.

To implement the city's bicycle facility network, motor vehicle lanes must often be removed to create space, resulting in a road diet. San Francisco is a walkable city where mass transit is heavily used and elevated freeways are being torn down rather than constructed. Nonetheless, the effects of road diets on all road users must be considered and sufficiently studied before final approval and implementation.

Valencia Street is a 62-foot 6-inch-wide street through a mixed use area of mostly two- to three-story buildings with commercial use at street level and residential units above, and metered on-street parking on both sides. The street lies in a grid pattern and is paralleled by four other north-south arterials. Before the project, the arterial was a four-lane street with an Average Daily Traffic (ADT) of approximately 22,000 vehicles per day. The #26 Muni bus, with a headway of 20 to 30 minutes, travels along the street. There is also a heavy pedestrian presence because the street is home to popular restaurants, nightclubs, and a variety of shops. All intersections have signals. A photo of Valencia Street with four lanes before the road diet is shown in Figure 1.

Valencia Street before the road diet, with two travel lanes and a parking lane in each direction.

Figure 1. Valencia Street before road diet.


Though the bicycle community wanted to see a road diet along Valencia Street, the local department of transportation was not willing to reduce capacity along this important north-south corridor. Valencia Street can be used as a surface street alternative to the Central Freeway, which was damaged by the 1989 Loma Prieta earthquake. Eventually, after a series of community meetings and public hearings, the San Francisco Board of Supervisors voted on a resolution in November 1998 that called for the removal of two travel lanes and the installation of bicycle lanes and a median lane for left turns on a one-year trial basis. In March of 1999, work was completed on the section of Valencia Street with Market Street at its north and Tiffany Avenue to the south, a length of approximately 1.8 miles.

After picture of Valencia Street, with one travel lane in each direction, a center left-turn lane, bike lanes, and parking lanes.

Valencia Street after road diet.

To minimize the loss of capacity along Valencia Street and reduce the impacts to parallel streets, signal timing was changed along Valencia Street and also along Guerrero Street one block to the west. On Valencia Street, the green time was maximized for the Valencia Street split while still maintaining time for pedestrians crossing Valencia Street. On Guerrero Street, the signal offsets were modified to promote a smoother progression at 25 mi/h, as the speed limit was lowered from 30 mi/h to address citizen concerns along the primarily residential street. The speed limit change and signal timing modifications were intended to address speeding concerns and help mitigate the likely increase of traffic along Guerrero Street.

Evaluation and Results

Before the work was started, baseline data were collected for use in a before-after report evaluating the road diet. As the initial project lasted for a one-year trial period, the results of the report would be presented at various public hearings so that the project could be voted on by the Board of Supervisors. If the project was rejected, the street would be returned to its previous four-lane configuration.

Traffic volumes were recorded along Valencia Street and the four parallel arterials to determine if and where there was spillover traffic from Valencia Street. Vehicle counts were taken automatically using pneumatic devices laid across the roadway at the same location on all five streets.

After determining the green times for Valencia Street, it was predicted that 10 percent of Valencia Street traffic would divert to parallel streets after the road diet was performed. Figure 2 shows before and after ADTs for the five roadways along the corridor. As expected, Valencia Street traffic volumes dropped by 10 percent.

Figure 2

A histogram of Average Daily Traffic on five San Francisco streets, before and after the road diet on Valencia.

Bicycle counts were taken along Valencia Street before and after. Ideally, counts also would have been taken on parallel streets to determine how much of the rise in bicyclists along Valencia Street was attributed to new bicyclists or to bicyclists transferring from parallel routes. Also, counts should have been adjusted to account for seasonal fluctuations in bicycling volumes.

A bicycle count taken on Valencia Street prior to the road diet showed 88 bicyclists per afternoon peak hour. After the road diet, a count yielded 215 bicyclists per hour, a 140 percent increase. As no counts were taken on parallel streets before the road diet, it is difficult to know what percentage of these bicyclists were new bicyclists or bicyclists from parallel streets. Speaking with bicyclists, it appeared that many were new bicyclists willing to try bicycling once they saw the bike lanes installed.

Collision data were also collected to determine if safety was improved with the new design. As the trial was for one year, the small amount of collision data meant that the findings in the before-after report were not statistically significant.

Table of collisions per month for Valencia Street, before vs. after road diet.

Bicyclists using Valencia Street in 2012.

Bicyclists using Valencia Street in 2012.
Photo by Dani Simons, via Flikr.

Total collisions declined by 20 percent, though the overall drop was less dramatic when one considers that the ADT along Valencia Street dropped by approximately 10 percent. Also, a signal upgrade project was completed along Valencia Street in 1997 that increased signal visibility and helped reduce the overall collision rate. Thus, it is difficult to come to any definite conclusions regarding the effect of this road diet on overall collision patterns along Valencia Street.

Although the project was initially controversial within the local department of transportation and some members of the community, the general consensus is that the project is a success. Bicycling along the street has increased dramatically and has made the street one of the most heavily used bicycle routes in the city. Collision rates for bicycling have dropped on the street. The merchants association has shown support for the road diet because it has made the street feel more like a destination than a through arterial. Even though a small amount of traffic spilled over to adjacent streets, it was likely that much of that traffic is through traffic with no intention of stopping along the street anyway. Thus, the fear that less traffic meant less business was not substantiated.

New configuration of Valencia Street, with the addition of a

New configuration of Valencia Street, with the addition of a "bike oasis," street trees, and information posts.
Source: San Francisco County Transportation Authority

Conclusions and Recommendations

Giving stakeholders plentiful opportunities to be involved in the process was an important aspect of the project's success. Also, the use of a trial allowed everyone to see how the project operated in real life before committing to it, which was especially useful for skeptics. It is important to have a trial of sufficient length (at least six months to a year) to allow changes in traffic patterns to come to an equilibrium. With any trial, the process should be made clear to the community so that there are no misguided expectations.

As this was the first trial road diet in the city, some data were not collected that would have been helpful. The effect on transit was not sufficiently studied. Travel time and delay studies for both transit and motor vehicles would have been helpful. Also, bicycle counts on parallel streets would have provided a better picture of where the increase of cyclists originated. While speed data would be helpful on road diet projects in general, the nature of Valencia Street is such that speeds are so variable given the short blocks, the changing traffic levels, the presence of double parking, etc., that collecting consistent before and after data would have been difficult.

Signs explaining Valencia Streets green wave.

Signs explaining Valencia Streets green wave.
Photo by Bryan Goebel.

The San Francisco Municipal Transit Authority (SFMTA) and the Department of Public Works have continued to improve bicycling conditions along Valencia Street. In 2008, the streetscape was improved on the two blocks from Duboce to 15th Street and on the seven blocks between 19th and 26th. From 2009 to 2010, a comprehensive streetscape improvement project was carried out on Valencia Street between 15th and 19th Streets. The project further calmed traffic on the street by removing the striped center median, which created space to widen sidewalks and parking lanes for the purposes of preventing "dooring" accidents. In some cases, curbside loading zones were redesigned for the purposes of preventing bike lane obstruction, and bulb-outs were added at some intersections and mid-block locations. On some of the bulb-outs, bicycle racks were added to create "bike oases."

Diagram of the bicycle bay at Market and Valencia, which helps bicyclists make the left turn onto Valencia

Figure 3: Bicycle bay at Market and Valencia to help bicyclists make the left turn onto Valencia.

Two additional projects on Valencia Street intersections were the first of their kind in San Francisco. In 2009, signal timing was adjusted on Valencia Street between 16th and 21st in a pilot project to improve vehicle flow and calm traffic. The traffic signals create a "green wave" for bicyclists and motorists traveling at a speed of around 13 mi/h, and were shown to reduce travel times for motorists by more than a minute at peak commuting times. In 2011, the pilot project was made permanent in the corridor. Finally, in 2012, an innovative bicycle bay was added to the intersection of Market and Valencia to help bicyclists make a left turn (See Figure 3).

All of the improvements along Valencia Street, starting with the road diet, were designed to reduce motor vehicle speed and create space for bicyclists, likely leading to a decrease in conflicts and collisions.

Costs and Funding

The road diet project cost $130,000 in 1999 for paint and sign work, and labor spent writing the report.

The comprehensive streetscape project between 15th Street and 19th Street cost $6.1 million and were funded by a combination of Federal surface transportation funds, two Transportation for Livable Communities (TLC) Federal grants, and local matching funds.


City and County of San Francisco Department of Public Works. Valencia Streetscape Project. 2013.

Sallaberry, M. Valencia Street Bicycle Lanes: A One Year Evaluation. San Francisco Department of Parking and Traffic, 2000.

San Francisco Municipal Transit Authority (SFMTA). SFMTA Unveils New and Enhanced Bicycle-Friendly Green Waves. 3 October 2013. Available:


Michael Sallaberry, P.E.
San Francisco Municipal Transportation Agency
Livable Streets Subdivision
One South Van Ness Avenue, 7th Floor
San Francisco, CA 94103
(415) 701-4563