Linear Referencing

Relationship Between Road Conditions and Accidents in North Carolina

Working for the city of Greenville, NC I have been tasked with analyzing car accidents on the roads of Pitt County to determine if there is a relationship between accidents and road conditions.

Before I analyzed the data I customized my ArcGIS Pro version 2.9 interface to stream line the linear referencing processes. The data was provided by NCSU GIS 520 course materials. First it was to create the linear referencing tab from the project tab at the top of the pro interface. Within the linear referencing tab I needed to add the groups: route, events and add-In. Within the groups I needed to add tools from the linear referencing toolbox. After saving my new interface I am able to continue with comparing the relationship between road conditions and accidents.

After adding my road and county data layers I needed to take my accident and pavement event tables into workable layer by using the make route event layer tool which will create dynamic segments of the layer. Accident data was collected as a point, the point where an accident happened, pavement data is a linear segment and the segments have data attributed to it such as a pavement rating. A pavement rating that is higher are rated as being in better condition than a pavement rating that is lower. I then used the overlay route events tool for the accident and pavements to view the relationship between the two. The overlay route event tool created a temporary table and to analyze the data of the overlay output I used the make route event layer tool again. I was able to see where the accidents happened, if the accidents occurred on a well maintained segment of road or a poor conditioned road.

Figure 1: Workflow Diagram Representing the Process to Show Relationship Between Road Conditions and Accidents In NC

Customizing the user interface ribbon is helpful in streamlining processes. Also using third party add-in are useful in future projects as well because ESRI’s ArcGIS Pro does not include all that is possible. Also, linear referencing is important because a part of a road, trail or railroad could have many different attributes across the linear data in which the data may change. Rather than having multiple tables to represent multiple attributes to the same linear data using a tool that can access data that has different attributes within it is easier and saves time.

Figure 2: Map Representing Accident and Pavement Relationship Near Greenville, NC

Another use of linear referencing is if a state wanted to know the spatial relationship between a deer-vehicle collision location and major roadway locations in order to reduce the amount of collisions.  The data needed are dead deer locations from a collision, which may be obtained from the local Department of Transportation or Department of Natural Resources.  The user would also need road data which may also be obtained from the Department of Transportation or freely available GIS data from the local government.  For data availability sake the user should focus on major roads and should sum the amount of collisions per major road and then join the sum data to the attribute table of the road.  If the deer collision data were to contain the mile marker location of the carcass we would then make a route event layer and then we could overlay the route events and generate a new layer from the data.  We could use the location data on where previous carcasses have been discovered and indicate to drivers the high volume of deer in the area in order for them to take safer actions or possibly the state could create an animal bridge for deer to safely cross the roadways.