Why is WSDOT measuring accessibility?
Sometimes the term “accessibility” is used in reference to the rules under the Americans with Disability Act. In this context, “accessibility” is about mobility; how people on the move reach their destinations.
When people travel, they generally do it with purpose: work, play, school, run errands, etc. Measuring accessibility brings WSDOT closer to figuring out what people care about when they travel – how difficult it is to reach their destinations by different travel modes. Accessibility measures take into account both the condition of the transportation system and the way the land is used in its service area. By measuring accessibility, WSDOT can:
- Identify multimodal mobility problems and opportunities for improvement, including those unrelated to the speed of vehicles – e.g. gaps in the multimodal network that hamper economic growth.
- Use engagement with stakeholders to help identify strategies that support prioritized modes (e.g. promoting demand management and transit-friendly roadway treatments along corridors with high-transit usage).
- Predict outcomes, track performance and weigh multimodal trade-offs (e.g. widening roadways may improve accessibility for people traveling in cars to regional destinations, but it may also reduce accessibility for vulnerable populations trying to cross to local destinations).
WSDOT is using accessibility metrics to…
- Better understand the link between environmental justice and health, and its effect on economic vitality.
- Evaluate multimodal accessibility around train stations.
- Develop a Level of Traffic Stress matrix that will help evaluate bicyclist and pedestrian comfort and mobility.
- Identify where the statewide demand response gaps are for the Human Services Transportation Plan.
How is WSDOT Measuring Accessibility?
WSDOT uses the GIS add-in, Sugar Access, to measure accessibility. This tool provides scores that rate access to destinations for each method of travel. It can also calculate travel times to certain types of destinations, and identify the number of that type of destination within “x” minutes of travel from the starting location.
We are able to determine:
- Points of interest, like schools, grocery stores, or parks (HERE, a navigation company).
- Jobs by type and earnings (LODES Longitudinal Employer-Household Dynamics Origin Destination Employment Statistics).
- Demographics like race, income, age, veteran and disabled status, and limited English-speakers (Census & American Community Survey).
- All-street network with average traffic speeds at four different times of day, number of lanes, turn restrictions, speed limits and other characteristics (HERE).
- Transit stops, routes and headways (GTFS).
- Bicycle and pedestrian networks with adjustable Level of Service ratings (based on facility type, number of lanes, and speed limit by default).
More about the tool and the data
How have others used accessibility metrics?
Virginia's Smart Scale. The Virginia DOT has measured accessibility improvements for the last three rounds of its Smart Scale project prioritization process and applied Sugar Access in its second round, with technical support from SSTI.
Hawaii's SmartTRAC (pdf, 12 mb). The Hawaii DOT applied accessibility metrics using Sugar Access for the first round of its SmartTRAC project prioritization in 2018, with technical support from SSTI and Smart Growth America.
Other accessibility examples from the following MPOs:
Contact:
Kyle Miller
Transportation Planning Specialist
360-705-7946
MilleKy@wsdot.wa.gov
