Abstract
In order to meet the goals set out in the City's landmark stormwater management plan, and to satisfy state and federal regulations, the Philadelphia Water Department (PWD) is planning, designing, and constructing a portfolio of stormwater infrastructure systems. These systems capture, filter, and store stormwater run-off utilizing sub-surface trenches, and vegetated features, from raingardens to street trees, mimicking natural processes where possible. As part of this program PWD has developed 156 stormwater stormwater management bumpouts, and anticipates bringing 342 more online within the next 5 years. These bumpouts have vegetated curb extensions that protrude into the street at mid-block or intersection locations. When located at crosswalks, curb extensions are thought to improve traffic safety by reducing the crossing time of pedestrians, improving visibility at intersections, and slowing drivers by reducing the turning radii at intersections.
This proposed project will examine the effects of these curb extensions over time on traffic collisions, injuries and fatalities relative to similar roadways where curb extensions will but have not yet been installed. Although pre-existing crash data featured in the selection of treated locations, the focus on stormwater management and long list of treated and untreated intersections provide unique, quasi-experimental conditions under which to examine the effects of curb extensions. Although curb extensions are widely accepted roadway design interventions in the fields of traffic calming and traffic safety, little is known about their effects on crashes or how these effects may vary by roadway conditions, location, or other features.
While data processing is in progress, the City and Water Department have geocoded the locations of the existing and proposed curb extensions. Crashes from PennDOT’s crash reporting system will be to the nearest intersection nodes of the eligible bump-outs. From here, the number of crashes, fatal and serious injury crashes, and injury crashes within each buffer can be counted and aggregated by year, with results associated with their corresponding intersection nodes and curb extensions.
Description
Timeline
Strategic Description / RD&T
Section left blank until USDOT’s new priorities and RD&T strategic goals are available in Spring 2026.
Deployment Plan
First quarter: assemble required databases
Second quarter: conduct analysis
Third quarter: Write up methods, analysis, and findings
Fourth: Present findings and submit for publication
Expected Outcomes/Impacts
This project will help City officials determine whether and to what extent its stormwater infrastructure system has created traffic safety benefits beyond the benefits of better managing storm water and preventing system overflow. The results will also provide findings about the effects of curb extensions on traffic safety using a causally valid quasi-experimental research design. These results can be used to help determine whether, where, and by how much curb extensions can be expected to improve traffic safety outcomes. The research may also provide insights into potential synergies between storm water management and traffic safety engineering.
Expected Outputs
The project will result in peer-reviewed journal publication as well as a report to the City of Philadelphia.
TRID
The existing literature on the effects of curb extensions focuses almost entirely on before and after studies by municipalities and studies of driver behavior and near misses. This would be the first published examination of effects on crash outcomes using a causally valid research design.
Individuals Involved
| Email |
Name |
Affiliation |
Role |
Position |
| erickg@upenn.edu |
Guerra, Erick |
University of Pennsylvania |
PI |
Faculty - Tenured |
Budget
Amount of UTC Funds Awarded
$90000.00
Total Project Budget (from all funding sources)
$180000.00
Documents
Match Sources
No match sources!
Partners
| Name |
Type |
| City of Philadelphia Office of Transportation and Infrastructure Systems |
Deployment Partner_ Deployment Partner_ |
| City of Philadelphia Water Department |
Deployment Partner_ Deployment Partner_ |
| City of Philadelphia Office of Transportation and Infrastructure Systems |
Deployment Partner_ Deployment Partner_ |
| PA Safe Roads |
Partner Partner |
