WSDOT - Active Transportation Route Directness Index Transects

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 12/31/2023 WSDOT LRS. Transects were only generated within Population Centers (using the Population Centers dataset obtained from the GIS Workbench in January 2025). Every 0.01 mile (52.8 feet) along the route a transect was created perpendicular to the route extending 500 feet on each side of the route. The begin and end points of each transect were then used to generate the shortest walking route between the two points. The Route Directness Index (RDI) is a ratio that compares the straight-line (crow-flies) distance from one point to another across a barrier 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 that out of direction travel creates. A complete discussion of route directness, including potential applications to decision making, can be found Washington State Multimodal Permeability Pilot, August 2021 [https://wsdot.wa.gov/sites/default/files/2021-11/MultimodalPermeabilityPilotReport-Aug2021.pdf]. 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.

本要素类（Feature Class）指代用于路线直达性指数（Route Directness Index，RDI）计算的断面线（Transect）。这些路线沿2023年12月31日发布的华盛顿州运输部（WSDOT）路线系统（Linear Reference System，LRS）所表征的州级道路递增生成。断面线仅生成于人口中心区域，所用数据集为2025年1月从GIS工作台（GIS Workbench）获取的人口中心数据集。沿路线每间隔0.01英里（即52.8英尺），即生成一条与路线垂直的断面线，该断面线向路线两侧各延伸500英尺。随后利用每条断面线的起点与终点，生成两点间的最短步行路径。路线直达性指数（RDI）是一项比值，用于对比两点间受障碍物阻隔的直线（即“飞鸟直线”）距离，与旅行者可利用的路径网络所实际产生的通行距离。鉴于绕行路径会额外增加出行时间、体力消耗以及天气暴露风险，RDI数据对步行及/或骑行出行场景尤为相关。关于路线直达性的完整讨论，包括其在决策制定中的潜在应用，可参阅《华盛顿州多式联运渗透性试点项目报告》（2021年8月）[https://wsdot.wa.gov/sites/default/files/2021-11/MultimodalPermeabilityPilotReport-Aug2021.pdf]。RDI可在不同尺度下开展分析。高层级的RDI分析可解答诸如比较全州范围内各人口中心的RDI数值，或是探究某一特定人口中心内部的RDI数值整体趋于一致，还是在区域内存在差异等问题。高层级RDI数据可与其他全州级数据集结合，如事故数据、公交站点（Transit Stops）、交通压力等级（Level of Traffic Stress）数据、出行目的地数据等，以分析潜在的相关性。不过高层级RDI数据在分析特定交叉口位置或针对高RDI数值提出解决方案时实用性较弱。若研究问题涉及走廊研究（Corridor Studies）或项目评估，则需开展更细致的分析。详细的位置信息可指向高层级路网地图未覆盖的关键目的地与交叉口位置。RDI的最低值为1，此时两点间可沿现有道路直接通行。本研究的方法学分析了以直线距离计约四分之一英里间距的起点与终点间的假想出行场景。在此类场景下，RDI为2意味着实际出行距离为直线距离的两倍，即约半英里。尽管半英里的距离并不算远，但RDI数值与实际出行距离无关。即便出行起点沿路线后移，只要RDI仍为2，实际出行距离仍会是最优直线距离的两倍。因此，RDI可衡量步行或骑行者所承担的实际或感知负担，以及出行成本。