UCLA Institute of Transportation Studies

The Los Angeles Department of Transportation (LADOT) initiated the Slow Streets program to create opportunities for multimodal transportation and outdoor recreation during the Covid-19 pandemic. The program initially used low-cost barricades and signage to demarcate Slow Street segments before upgrading to six new traffic calming measures, or countermeasures, in Phase 2 that were designed to reduce speeds. This report evaluated their effectiveness through analyzing StreetLight speed data and employing a custom formula comparing speed changes on Slow Street segments to estimate each countermeasure’s speed-reducing effect. Nearly half of the segments experienced speed increases after countermeasure installation. Though it was difficult to attribute these speed increases to any reasons with certainty, we speculate that the countermeasures may not have caused great enough changes in street geometries to significantly alter driver behaviors and reduce speeds. Drivers may be using Slow Street segments to “cut through” traffic, and Slow Streets may not have been able to evade speed increases that have occurred on many streets during and after Los Angeles’ stay-at-home orders went into effect. Based on the results, LADOT should prioritize the installation of treatments located at or near intersections, which have shown to be most effective. LADOT should also reduce lane widths on entire street segments rather than at certain points along the street and consider alternative materials to work around current design restrictions. Finally, LADOT should perform a qualitative study of the effectiveness of the program and improve information access of the Slow Streets network by publishing interactive maps online.