OakDOT: Using GIS Data to Prioritize Traffic Safety Service Requests

Everyone deserves access to safe transportation options, whether they are driving, walking, riding a bike, or using public transit. Yet data from the U.S. Centers for Disease Control show that more than 36,000 people in the U.S. were killed in traffic-related incidents in 2019. It was the leading cause of death for people aged 5 to 24, and the second leading cause of death for all other age groups under 85. According to the Safe Routes for Schools National Partnership, low-income communities and communities of color are more likely to experience traffic-related injury and death.

Infrastructure improvements can help calm traffic in high risk areas. Traffic signs, pavement marking, and small-scale traffic calming devices can be implemented quickly and at relatively low cost. In an effort to reduce traffic-related injuries in their community and ensure equitable services, the City of Oakland Department of Transportation (OakDOT) Traffic Safety Request Program uses a data-driven approach to deliver quick-build improvements to problematic intersections and street segments.

A Data-Driven Approach

The city integrated their Cityworks public asset management platform with SeeClickFix, a 311 request and work management app that bridges the communication gap between residents and their local government. Known as OAK 311, the app allows residents to report problems they encounter in their community. These reports are then sent to Cityworks as service requests. Residents can use the traffic safety category in the app to request quick-build traffic safety improvements such as signage, pavement markings, and traffic calming devices. 

OAK 311 has been so successful that many city departments, including OakDOT, receive more service requests than their resources can handle. 

OakDOT created a data-driven prioritization model that leverages Cityworks and ArcGIS to assign a priority score, or value, to each street segment in the community. As a result, service requests are automatically given higher or lower priority depending on their geographic location. The goal of this data-focused approach is to promote equity in the community by ensuring that traditionally underserved and high-risk areas are not overlooked. 

Prioritization scores are based on three core variables: traffic collision history, land use proximity, and equity. 

Each of these factors is weighted equally (33 percent) to calculate the final prioritization score. Once the final prioritization scores are calculated, they are assigned to their respective street segments in GIS. Cityworks then incorporates the GIS layer, provides map visualization, and displays the final prioritization scores in the context of the Cityworks map. When a service request comes in, either from OAK 311 or by other means, the prioritization score is automatically assigned from the respective street segment where the request is located. This creates a system of record that allows city employees to filter, organize, and report on work activities by their assigned prioritization scores.

Traffic Collision History

Traffic collision data not only correlates directly with the types of service requests being submitted, but also aligns with the City of Oakland’s focus on creating equity in the community. Historic crash data shows that certain demographic groups and geographic areas within the city experience a disproportionate number of traffic incidents compared to others. 

This factor is calculated by pulling traffic collision data from the state of California’s Statewide Integrated Traffic Records System (SWITRS), a database that collects and processes traffic collision statistics and information gathered from collision scenes. The City of Oakland translates the SWITRS data into a collision database using a proprietary software called Crossroads.

The city further analyzes the SWITRS collision information and assigns each incident an individual score using an Equivalent Property Damage Only index (EPDO). The EPDO is a number-based index that assigns a weighted score to traffic incidents according to their severity. For example, a car crash that involves a fatality receives a 9.5, the highest EPDO score, whereas a minor collision with no injuries receives a 1.0, the lowest score. 

Once the SWITRS and EPDO index data has been analyzed and assigned a score, it can then be visualized in ArcGIS as a heatmap with a street layer added to identify where the most severe collisions have occurred. With the data in GIS, each street segment within the City of Oakland is assigned its respective traffic collision prioritization score—the first factor in determining the overall prioritization score.

Land Use Proximity

The City of Oakland also prioritizes locations adjacent to places where vulnerable populations travel. Schools were the first land use category to be used for this calculation. The city drew polygons around the school’s parcel location, marking each of the street segments within a 500-foot radius to increase the prioritization score. In 2021, OakDOT updated the model to include a 500-foot radius around point locations of a wider range of land use categories, including libraries, senior centers, health clinics, major transit stops, and more.

Demographics

Knowing that transportation activities have a demonstrated history of being more dangerous and less accessible to vulnerable populations, OakDOT wanted to ensure that disadvantaged neighborhoods were being properly being taken care of and not overlooked. They therefore chose equity as one of the factors to determine overall prioritization, becoming one of the first cities to adopt an equity component as a determinant of service. 

This methodology has been regularly refined. As of 2021, the OakDOT equity index uses seven demographic factors to determine the level of priority for a census tract or neighborhood: race, income, disability status, educational attainment, age, single parent households, and rent burden. Neighborhoods are assigned a prioritization rating on a scale from lowest to highest, and street segments within each neighborhood then receive a corresponding score.

A public dashboard includes interactive tabs for exploring the relationships among demographics, geography, and various health impacts in Oakland.

The Future of Prioritization Scoring

Cityworks and ArcGIS provide a succinct way to organize, manage, and maintain prioritization data and service requests, allowing OakDOT to view their prioritization scores in a GIS-centric manner. As new data is received from SWITRS and censuses, and new priority facilities are built, the City of Oakland can easily go into Cityworks and ArcGIS and update their prioritization data to reflect the most up-to-date information. 

The combination of these three prioritization factors has helped OakDOT use a variety of valuable data to inform their service strategy. It has given them a rational and data-driven way to optimize and streamline traffic infrastructure updates in the community and allows them to make the most of their limited resources to execute projects that bring the highest equitable return.

A public map shows Oakland street segments highlighted with their combined prioritization scores.

By Westley Cottam and Sara Adelman, Cityworks contributing writers