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Layer: Active Transportation Route Directness Index Transect (ID: 5)

Name: Active Transportation Route Directness Index Transect

Display Field: RDI_Identifier

Type: Feature Layer

Geometry Type: esriGeometryPolyline

Description: This feature class represents the transects that were used for the Route Directness Index calculation. These lines were generated along the increasing state routes as represented by the 12/31/2021 WSDOT LRS. Transects were only generated within Population Centers as defined by the 2021 Active Transportaiton Plan. Every 250 feet along the route a transect was created perpendicular to the route extending 500 feet on each side of the route. The end points of each transect were then used to calculate the direct distance between the endpoints and were used to generate the shortest walking route between the endpoints.The Route Directness Index (RDI) is a ratio that compares the straight-line (crow-flies) distance across a barrier and between two points to the actual distance imposed by the network of paths available to a traveler. RDI data is particularly relevant to pedestrian and/or bicyclist trips due to the extra time, physical energy, and exposure to weather out of direction travel creates. Research indicates that pedestrians are especially sensitive to out of direction travel and Broach, 2016, found that "to avoid an additional unsignalized arterial crossing, a pedestrian would be willing to go over 70 meters (230 feet) farther via an alternate path." This finding suggests that route directness is relevant to considerations of both utility and safety with respect to active travel. A complete discussion of route directness, including potential applications to decision making, can be found Washington State Multimodal Permeability Pilot, August 2021.RDI can be analyzed at different scales. A high-level analysis of RDI can address questions that compare population centers across the state or consider whether the RDI values are generally similar within a given population center or tend to vary in different portions of a population center. High level data could be combined with other statewide data such as crash data, transit stops, level of traffic stress data, destination data, etc. to analyze potential correlations. High level RDI data is less useful for analyzing a particular crossing location or recommending solutions to address high RDI values. A more detailed analysis is likely required when questions involve corridor studies or project evaluations. Detailed location information can refer to key destinations and crossing locations that are not captured using higher level network maps.The lowest RDI is 1 because a trip between those points can be made directly along an existing roadway. The actual methodology analyzed hypothetical trips where the start and end points were about a quarter mile apart relative to a straight line. In such a situation, an RDI of 2 would mean the trip is twice the distance it might otherwise be, or about one-half mile. Although one-half mile is not particularly far, the RDI is independent of the actual distance. We might start further down the road and if the RDI remained a 2 our trip distance would be twice as long as it could have been. The RDI thus measures the real or perceived burden or travel cost incurred by a person walking or bicycling. An RDI of 2 was selected as the threshold where that travel cost makes it increasingly unlikely that an active travel trip would be completed. The “design vehicle” when selecting that threshold was a walking pedestrian. Selecting an RDI of 2 was an attempt to balance observed travel behavior and the realities of existing crossing opportunities along the state highway system. In addition, since this analysis used about a quarter-mile spacing between test destinations, an RDI of 2 corresponds to the one-half mile maximum distance transit planners assume a pedestrian will be willing to walk to catch a bus or train. (FHWA, Pedestrian Safety Guide for Transit, 2013) So with respect to multimodal trips, RDIs greater than 2 might make transit less attractive.

Copyright Text: Washington State Department of Transportation

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