SAFE TRANSPORTATION FOR EVERY PEDESTRIAN CASE STUDY

Seattle's New-and-Improved Proactive 

Approach to Pedestrian Safety

Seattle, Washington

KEY ELEMENTS:

Systemic Pedestrian Safety Analysis

Data-Driven Countermeasure 

Implementation

While Seattle’s population continues to grow, the 

number of overall traffic-related fatalities continues 

to trend downward. However, pedestrian and cyclist 

crashes have remained relatively steady. To meet 

the growing demand while improving safety, the City 

developed the Bicycle and Pedestrian Safety Analysis 

(BPSA), a robust approach to modeling pedestrian and 

bicyclist safety.1

 Seattle is using the analysis results 

to encourage consideration of pedestrian and cyclist 

safety and countermeasure implementation in project 

development. 

BACKGROUND ON SEATTLE'S BPSA

The City of Seattle Department of 

Transportation (SDOT) first implemented 

the Bicycle and Pedestrian Safety Analysis 

(BPSA) in 2016 as a data-driven approach 

for understanding where, how, and why 

crashes involving pedestrians and bicyclists 

happen.2

 Phase 1 laid the foundation 

for conducting the statistical analysis. It 

included pedestrian and bicycle crash 

data from 2007 to 2014, as well as roadway, 

demographics, transit, lighting, traffic signal 

presence, and pedestrian and bicyclist 

volume data.

PHASE 2 IMPROVEMENTS

Phase 2 of the BPSA concluded in early 

2020. It involved updating the statistical 

models and incorporating new features 

into the analysis. The analysis now includes 

three more years of crash data (2014-2017). 

Additionally, Phase 2 expanded the traffic 

signal modeling functionality from a binary 

measure of traffic signal presence to a more 

detailed analysis of signal phasing data.

The most significant BPSA update during 

Phase 2 involved improvements to the 

exposure model used to estimate the 

number of events that could potentially 

result in a crash. While Phase 1 incorporated 

pedestrian and cyclist trip-generation data, 

Phase 2 expanded on an overall exposure 

model while including a reliable vehicle 

volume estimate model across Seattle’s 

entire street network to complete the 

exposure analysis.

For more information, please contact:

Chris Svolopoulos, City Engineer, SDOT

Chris.Svolopoulos@seattle.gov | 206.684.5312

Figure 1. Graphic. Pedestrian crash types used to build statistical 

models for Seatlle's BPSA. 

©2019 SDOT.
Case Study: Robust Pedestrian Safety Analysis in Seattle

PEDESTRIAN SAFETY ANALYSIS

SDOT developed safety performance 

functions (SPFs) for four different pedestrian 

crash types at intersections: all pedestrian 

crashes, vehicle turning right crashes, 

vehicle turning left crashes, and vehicle 

traveling straight crashes. SPFs are statistical 

models used to estimate crash frequency 

at a location. Phase 2 of BPSA built on 

the SPFs developed for Phase 1, focusing 

on improving certain model inputs and 

statistical techniques.

SAFETY IMPACTS OF BPSA

SDOT strengthened the systemic impact of 

the BPSA by incorporating it into the existing 

Complete Streets Checklist process used to 

identify project improvements for all road 

users. If a project includes a BPSA-identified 

location, the project is reviewed for potential 

pedestrian and/or bicycle improvements. 

This approach has led to a cultural shift 

within SDOT, where traffic and design 

engineers have become more accepting 

of proposed countermeasures at sites 

identified by BPSA’s rigorous analysis.

This data-driven approach has had other 

positive impacts on pedestrian safety in 

Seattle. While the City’s Vision Zero plan 

serves as the motivation for many safety 

policies and programs, BPSA provides 

the quantitative support and justification 

to deploy safety countermeasures. 

For example, SDOT used BPSA data to 

support an increased implementation of 

Leading Pedestrian Intervals (LPIs), from 15 

intersections at the time of Phase 1 to 145 at 

the end of Phase 2.

“The biggest value of BPSA is that it’s proactive 

and systemic. It’s sort of a diving board for traffic 

engineers, giving them ideas about where to 

implement improvements. It’s also very helpful for 

informing people who make those decisions.” 

– Chris Svolopoulos, Civil Engineer, SDOT

References 

1SDOT. City of Seattle Bicycle and Pedestrian Safety Analysis Phase 2. http://www.seattle.gov/Documents/

Departments/SDOT/VisionZero/SDOT_Bike%20and%20Ped%20Safety%20Analysis_Ph2_2420(0).pdf. February 4, 

2020. 

2SDOT. City of Seattle Bicycle and Pedestrian Safety Analysis. https://www.seattle.gov/Documents/Departments/beSuperSafe/BicyclePedestrianSafetyAnalysis.pdf. September 30, 2016. 3SDOT. "A Big Step Forward for Pedestrian Safety." https://sdotblog.seattle.gov/2019/06/17/a-big-step-forwardfor-pedestrian-safety/. June 17, 2019. 

Figure 2. Photo. Pedestrians cross during the LPI at an intersection 

in downtown Seattle.

3

LESSONS LEARNED AND NEXT STEPS

The City of Seattle identified key lessons

learned throughout the first two BPSA

phases. First, it is important to identify

locations both where there is data and

where there is a lack of data. Seattle used

this information to perform optimization

for future pedestrian and bicycle count

locations, which will inform future modeling

efforts. Second, an agency should

geolocate pedestrian and bicycle collision

data and implement quality control

measures.

SDOT plans to continue to upd

©2019 SDOT.

STEP: https://safety.fhwa.dot.gov/ped_bike/step/