Evaluation of Countermeasures: A Study on the Effect of Impactable Yield Signs Installed at Intersections in San Francisco


The present study evaluated the effect of impactable signs that used the yield-symbol as approved by the National Committee on Uniform Traffic Control Devices (NCUTCD) in the 2003 Manual of Uniform Traffic Control Devices (MUTCD). Impactable yield signs are low-cost signs constructed of flexible material. The signs were installed in the medians adjacent to crosswalks at selected non-signalized intersections to instruct drivers to yield the right-of-way to pedestrians. This paper examines the effect on safety characteristics of the intersections of these signs at three stop-sign controlled intersections in San Francisco over two follow up periods. Since these signs were installed recently, there were no post-installation crash data for comparison with the preinstallation crash data. As such, surrogate measures, including (a) driver yielding behavior, (b) conflicts among drivers and pedestrians crossing the intersection, (c) waiting time for pedestrians, and (d) time taken by pedestrians to cross a given crosswalk were documented. Previous studies have indicated that impactable yield signs are effective in increasing the rate of drivers yielding to pedestrians. Video recordings were taken at the intersection pre- and post-installation to observe any changes in behavior. Analyses of these recordings yielded data for baseline and the first and second follow-up periods respectively. Testing the first and second follow-up data against the baseline data reveal that, a substantial increase in yielding behavior by drivers occurred immediately after installationas well as during the second follow-up period. No significant effect was observed in any other variables.

Ragland, David R.
Publication date: 
April 1, 2007
Publication type: 
Conference Paper