Most people don’t go out the door to the street for no reason; they have a destination in mind. They are going to work, to school, to shop or play. Measuring accessibility helps WSDOT evaluate what people care about when they travel – the ease of reaching destinations by different travel modes. Accessibility measures account for both transportation network conditions and the land uses those networks are meant to connect.
Using Sugar Access
WSDOT uses the GIS add-in, Sugar Access, to measure accessibility. For instructions on downloading and using Sugar Access, visit Citilabs’ website.
- Points of interest like schools, grocery stores, or parks (data provided by 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 (drawn from data collected by the U.S. Census & American Community Survey). Additional demographic data are available via the Washington Tracking Network, which is maintained by the Washington State Department of Health.
- All-street network with average traffic speeds at four different periods during the day, number of lanes, turn restrictions, speed limits, and other attributes (HERE)
- Transit stops, routes and headways (General Transit Feed Specification)
- Bicycle and pedestrian networks with customizable Level of Service ratings (based on facility type, number of lanes, and speed limit by default). (Note that the forthcoming Washington Active Transportation Plan (2019) will also provide a network analysis of pedestrian and bicycle conditions.)
The networks and land use data can be edited in ArcMap and the data can be analyzed at the block or block group level.
You can use WSDOT’s standardized accessibility metrics, which are evaluated statewide based on block groups. More information on methodology and web maps available on WSDOT’s Online Map Center.
- Access to Jobs. The number of jobs reachable by driving, transit, biking, and walking weighted based on their travel time from each zone.
- Access to Non-Work Destinations. Access to non-work destinations by driving, transit, biking, and walking with different weightings for different destination types.
- Standardized Access to Jobs. The number of jobs reachable on the transportation network as a proportion of the total number of nearby jobs, to account for different urban contexts.
- Standardized Access Gap. The difference between actual network accessibility and optimal accessibility, weighted by the number of households or low-income households.
- Accessibility Diagnostic. Identifies whether gaps in access to jobs or non-work destinations are caused mainly by traffic congestion or network circuity.
- Commuter Mode Shift Potential (Driving to Transit). Access to jobs by transit as a percentage of access to jobs by driving.
- Non-Commuter Mode Shift Potential (Driving to Transit). Access to non-work destinations by transit as a percentage of access to non-work destinations by driving.
Customize your analysis with Sugar Access
You can also customize your accessibility analysis using Sugar Access and measure changes in accessibility from transportation projects or changes in land use. For instructions on downloading and using Sugar Access, visit WSDOT’s Multimodal Accessibility page or see additional resources below.
- Open Access Score: Evaluates minimum travel time to a select destination type, the number of destinations accessible within a given travel time, or the travel time-weighted sum of destinations.
- Access Score Work: Evaluates the travel time weighted sum of destinations, like Open Access Score, with an emphasis on jobs.
- Access Score Non-Work: Evaluates an individual’s ability to reach a basket of non-work destinations (valued from 1 to 100)
- Scenario Analyzer: Compares the change in accessibility based on different transportation or land use scenarios
- Demographics of Households
- Type of Work Destination (Jobs of All Types or Specific Jobs Based on Industry or Wages)
- Type and Weighting of Non-Work Destinations (Point of Interest Type)
- Time of Day (AM Peak, Midday, PM Peak, Off Peak)
- Mode of Travel (Auto, Transit, Bike, Pedestrian)
- Average walk, bike, and auto speeds, to reflect relevant context (for example, locations that serve high numbers of seniors, children, and people with disabilities will typically have slower average walking speeds than locations that do not).
- Adding or removing transportation network links
- Changing the speed and other attributes of links (in GIS or using a lookup table).
- Adjusting the average walking and biking speeds.
- Adding or removing land uses (jobs, households, POIs, etc.).
- Defining new travel time decay functions, which reflect people’s preference for shorter trips by penalizing further destinations (i.e. a job 15 minutes away will be more valuable than a job 30 minutes away).
- Incorporating more detailed information from existing data (e.g. local sidewalk GIS layers) using available pre-preprocessing tools.
Accessibility analysts can edit the roadway or transit network to change, add, or remove a roadway link or transit route.
Mobility Performance Framework measures and metrics applicable to Sugar Access
Economic Vitality Framework measures and metrics applicable to Sugar Access
|GOAL||PERFORMANCE MEASURE||PERFORMANCE METRICS||ANALYSIS SOFTWARE|
|Quality Of Life||Access to affordable housing||Average housing and transportation costs in a specified geographic area as a percentage of household income||Sugar Access|