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close windowCase Study No. 63
San Francisco, CA
Information provided and contributions made by DKS Associates and Frank Markowitz, Department of Parking and Traffic, City and County of San Francisco.
Pedestrian and vehicle conflicts were occurring almost daily at several intersections in San Francisco.
Pedestrian interviewees found the countdown signals helpful in understanding the amount of time left for crossing.
Pedestrian countdown signal heads show the time remaining for each phase.
The City and County of San Francisco, along with other cities around the country, has been concerned about pedestrian safety at intersections in the City. The City is home to a bustling pedestrian-scaled landscape where thousands walk to work, shopping, dining, and other activities. The thousands of tourists that come to San Francisco each year increase the number of people walking in the City. After a time when pedestrian conflicts with cars were occurring almost on a daily basis, the City’s Department of Parking and Traffic looked into ways to increase the safety of pedestrian crossings at signalized intersections.
San Francisco Department of Parking and Traffic (DPT) is currently conducting a test of pedestrian countdown signals citywide. The pilot program involves 14 intersections, with a range of physical and socio-cultural environments. Installation began in late March 2001. As of June, installation had been completed at nine intersections. Two were added in August 2001. The remaining three locations were to be installed in fall 2001 under a City and County of San Francisco signal modification contract.
The California State Auto Association (CSAA) is the primary funding entity of the pilot program and also is taking responsibility for installation and maintenance at 10 intersections. CSAA also assisted with public information, and the organization is working on a video and Public Service Announcement about pedestrian intersection safety, which will address countdown signals.
As a condition of CTCDC and FHWA approval, DPT was required to do an evaluation of the effectiveness of the countdown signals (CDS). DPT did substantial pre-installation and post-installation data collection regarding pedestrian behavior and attitudes, as well as driver behavior. Data collection was performed by DPT employees, primarily college student interns, under the direction of DPT professional staff. With assistance from the Metropolitan Transportation Commission (MTC), the consulting firm of DKS Associates was retained to perform the evaluation. This case study is a brief summary of their preliminary evaluation. A more extensive evaluation is expected to take place 6 to 12 months after installation.
“Before and after” comparisons may have been affected by seasonal factors and field crew differences that were impossible to avoid. The pre-installation data collection was chiefly done in May 2001, while schools were still in session, while post-installation data collection was primarily done in June and July 2001, during peak vacation periods. Changes in the proportion of students and tourists at some intersections could have influenced the results. It was also not possible to use the same personnel for pre- and post-installation field work, and results could be affected by differences in field workers’ interview style and attentiveness.
The most important findings of the study are the following:
Each of these results is positive. While it is too soon to make a statistical analysis of improved pedestrian safety resulting from these behavioral results, it is reasonable to conclude that the number of pedestrian collisions is likely to decrease.
The number of pedestrians who finished crossing on red dropped from 14 percent to 9 percent at eight observed intersections. This result is due mostly to walkers hurrying across (more often finishing on the yellow), rather than being more compliant with pedestrian signals. There was little change in when pedestrians started crossing. There was a slight decrease in pedestrians starting to cross during the flashing red hand (flashing DON’T WALK) and a similar, slight increase in pedestrians crossing during the solid red hand.
The proportion running or aborting their crossing significantly decreased, dropping from combined 13 percent to 8 percent. Observed vehicle/pedestrian conflicts also dropped from 6 percent to 4 percent of pedestrians. The latter is consistent with separate set of observations of vehicle/pedestrian conflicts, showing a reduction in the proportion of motorists in conflict with pedestrians.
Data collection was complicated by the change in pedestrian signal timing that accompanied countdown signal installation. San Francisco is gradually changing signal timing so that the solid red hand begins at the start of the yellow vehicle indication, rather than at the end of the yellow, as has been the historic practice. However, this change was taken into account in data analysis.
Pedestrian behavior findings varied significantly depending on location. This could have been due to actual differences--due to different walking populations and different physical environment--or to unintentional changes in data collection procedures.
Interviewees finding pedestrian signals “very helpful” increased substantially with the countdown signals—only 34 percent with conventional signals, but 78 percent with countdown signals. About 92 percent of post-installation interviewees explicitly said the countdown signals were “more helpful” than conventional pedestrian signals, primarily because they showed the time remaining to cross. This is consistent with recent FHWA research that showed that a pedestrian sample strongly preferred the countdown signal to actual and theoretical versions of pedestrian signals, and that the countdown version was “most easily understood.” Only 6 percent said the conventional pedestrian signal was more helpful. In these few cases, one likely reason was the decreased size and clarity of the walking person/red hand symbol.
Also, 82 percent of post-installation interviewees had noticed the countdown signals before the interview started. Some 69 percent said they were crossing differently. Few (17 percent) understood that it is a violation of the vehicle code to start crossing during the countdown (flashing red hand). This compares to 40 percent in the pre-installation study. This suggests that pedestrians are using the countdown signals to decide when to start to cross, which is not its official purpose in San Francisco. Also, it underscores that a substantial proportion of pedestrians do not understand pedestrian signals.
These figures illustrate the confusion that exists nationally about the meaning of the flashing red hand as documented in a recent ITE study. The City and County of San Francisco urges further study of the flashing red hand, comparing its use in the U.S. and abroad, as well as pedestrian attitudes. While the understanding of the meaning of the flashing red hand is a concern, the City and County of San Francisco believes that the behavioral improvements brought about by the countdown signals outweigh the issue of whether pedestrians understand the legal interpretation of the flashing red hand. The finding that, behaviorally, pedestrians are not more likely to leave the curb during the flashing red hand is especially important in this regard.
Interview findings were extremely consistent across all locations. For example, at all nine intersections, at least 87 percent of respondents stated that the countdown signals were “more helpful” than conventional pedestrian signals.
There was a small decrease in the reported incidence of red light running (drivers entering the intersection on red), from 2 percent to 1 percent (not statistically significant). A less important finding was a slight decrease in drivers finishing crossing the intersection on the red reported after CDS installation.
A more rigorous study of driver behavior and human factors in Monterey found that unsafe driver behavior was not a problem, although concerns have been raised that drivers will use the countdown to decide whether to speed up on a “stale green.” The Monterey study found that by the time drivers could see and interpret the countdown signal, it would be generally too late for them to change their behavior.
The impact at different intersections needs to be compared in order to identify at which locations, the devices are most effective. DKS Associates suggested that the highest priority should be for the following type of intersections:
With California’s energy crisis, San Francisco and other cities face major financial incentives to replace existing traffic and pedestrian signals with more energy-efficient LED (Light Emitting Diode) versions. Since there are LED countdown signals available, this presents an opportunity to change to countdown signals at many or most signalized intersections with no incremental cost. In fact, the incremental cost is roughly $1,000 per intersection ($130 per signal head) for countdown versus conventional LED pedestrian signals, which can be absorbed from in-kind state grant and County sales tax funds. Therefore, San Francisco seeks permission to expand the countdown signal experiment to all locations with existing or planned pedestrian signals, with the exception of narrow streets of less than 12.2 m (40 ft) between curbs or possibly a very few industrial locations with minimal pedestrian volumes.
San Francisco will continue and expand the countdown signal evaluation. This will also be useful in determining how effective the devices are when they are so widespread that there is no novelty factor. This case study is a preliminary evaluation of San Francisco’s pedestrian signal countdown program.
Frank Markowitz
Pedestrian Program Manager
Department of Parking and Traffic
City and County of San Francisco
25 Van Ness Avenue #345
San Francisco, CA 94102
Phone: (415) 252-4696
E-mail: frank_markowitz@ci.sf.ca.us