Moving Toward Spatial Access: Lessons Learned Daniel Carter UNC Highway Safety Research Center Presented at the Traffic Records Forum, August 6, 2017 New Orleans, LA

Background HSIS roadway and crash data warehousing process involves: Acquiring data Managing data Delivering data Data format has always been flat or tabular files

Background Traditionally fulfilled data requests in tabular format: Roadway segments of a certain type with crash counts attached Crashes of a certain type with roadway characteristics attached

Background States are increasingly using GIS format for crash and roadway data Development of the spatial road network is the result of the previous “centerline based” road inventory adapted to a spatial map to fulfill federal reporting requirements Researchers want spatial data How does the HSIS process need to change to accommodate spatial data?

Objective Develop a process for creating a spatial representation of HSIS data

Staffing UNC HSRC – Daniel Carter, David Harkey, Forrest Council UNC Carolina Population Center – Brian Frizzelle

How We Started Initial plan: Pilot state – Ohio Replicate the HSIS process (acquire, manage, distribute) all within the spatial environment Use the spatial data (road and crashes) available from the states Pilot state – Ohio Acquired Ohio roadway and traffic data from their website Acquired one year of spatial crash data (2013) from Ohio DOT staff

Problems Differences in number of road segments 525,000 segments in spatial vs 32,000 segments in HSIS tabular file Differences in number of crashes HSIS tabular data only has state road crashes; spatial data has all public road crashes Differences in attributes/fields only about a 40% match in specific fields between spatial and HSIS tabular road files

New Plan Continue to use HSIS tabular (traditional) data as the basis for all parts of the process Use spatial data only for spatial position This was the turning point

New Challenge We could not simply use the spatial network available online from the state We wrongly expected that the route naming convention would be the same between the traditional roadway data (what HSIS has been receiving) and the spatial roadway data Some were radically different (CA) and some were slightly different (NC)

New Challenge We had to work with each state to figure out their route naming scheme in the spatial data and how to translate that to match up to the route ID system used in HSIS roadway data We created “custom” HSIS spatial road networks for each state (added route ID fields to allow joining to HSIS data) NLF_ID CATHCR00232**C cntyrte ATH0232R

New Process Custom spatial files developed for various years, depending on the availability from the state: CA: 2014 MN: 2012-2014 NC: 1999-2015 OH: 2009-2013 WA: 1999, 2002-2015

New Process Develop HSIS tabular output (road segments or crashes) to fulfill data request New optional last step: Convert data request to spatial format Map road segments or crashes as route events in GIS, using the custom spatial network as the “skeleton” Export as shapefile or feature class Deliver to data requester

Modifications to Annual Process Additional Steps for Spatial Data Acquire data Acquire current version of spatial road network Ensure that the network contains all attributes needed to merge with HSIS tabular data Manage data Identify route IDs Modify route IDs as needed to match HSIS route designation. Create LRS routes if the State’s spatial data does not contain LRS routes Deliver data Convert HSIS tabular data to ArcGIS readable format Develop spatial file for data delivery  

Modifications to Annual Process Additional Steps for Spatial Data Acquire data Acquire current version of spatial road network Ensure that the network contains all attributes needed to merge with HSIS tabular data Manage data Identify route IDs Modify route IDs as needed to match HSIS route designation. Create LRS routes if the State’s spatial data does not contain LRS routes Deliver data Convert HSIS tabular data to ArcGIS readable format Develop spatial file for data delivery  

Modifications to Annual Process Additional Steps for Spatial Data Acquire data Acquire current version of spatial road network Ensure that the network contains all attributes needed to merge with HSIS tabular data Manage data Identify route IDs Modify route IDs as needed to match HSIS route designation. Create LRS routes if the State’s spatial data does not contain LRS routes Deliver data Convert HSIS tabular data to ArcGIS readable format Develop spatial file for data delivery  

Modifications to Annual Process Additional Steps for Spatial Data Acquire data Acquire current version of spatial road network Ensure that the network contains all attributes needed to merge with HSIS tabular data Manage data Identify route IDs Modify route IDs as needed to match HSIS route designation. Create LRS routes if the State’s spatial data does not contain LRS routes Deliver data Convert HSIS tabular data to ArcGIS readable format Develop spatial file for data delivery  

Issues (and Opportunities) for the Future Data delivery will likely be solely in spatial format Available attribute data may change Much more non-state mileage available Spatial linework is/will be stored separately for each direction of a road Defining a single section of road may be difficult Crashes may begin to be attributed to one side or the other Volume data may be split across the sides of the road Difficult in the short run, but may provide enhanced safety analysis possibilities in long run

Questions and Discussion