By: Dev Davis, Misa Fujisaki, Miho Tanaka, Lucy Xiao
Over the past 6 weeks, our team of four Stanford University Public Policy graduate students conducted a social cost-benefit analysis of the Lincoln Avenue “road diet” initiative to provide
the City of San Jose with a comprehensive overview of the social costs and benefits associated with this road diet.
Using data provided by the City of San Jose, we first conducted a rigorous statistical analysis of pre- and post-diet traffic counts and speeds, historical collision data for Lincoln Avenue, Lincoln
Avenue driving times, and bicyclist and pedestrian counts. We confirmed significant traffic count and speed reductions on Lincoln Avenue during the road diet, although the data indicate that
these effects were smaller than indicated in the city’s official report. We also found a positive upward trend in the number of bicyclists and pedestrians on Lincoln Avenue after the diet. However, these findings were not statistically significant, likely due to the small number of observations. For Lincoln Avenue driving times, results were mixed, with a decrease in average
driving time during the middle of the day and an increase in average driving time during the evening rush.
We then combined these outcomes with results from existing academic literature to conduct a social cost-benefit analysis of the road diet. Given the currently available data, we find the overall net effect of the road diet to be inconclusive. The benefits of the road diet may or may not outweigh the costs depending on three main factors: (1) the actual reduction in collisions; (2)
the road diet’s impact on livability for area residents; and (3) the road diet’s impact on sales for Lincoln Avenue businesses.
Based on these results, we recommend that the City of San Jose:
● Clarify and prioritize the goals of the road diet to better gauge whether the road diet successfully achieves its policy objectives.
● Determine the road diet’s impact on Lincoln Avenue businesses by gathering and analyzing pre- and post-diet data on business sales receipts.
● Survey area residents to gauge perceptions of the road diet’s impact on livability.
● Gather more pedestrian and bicycle traffic count observations over a longer time period to determine if the post-diet increases are statistically significant.