Guest post by Jonah Finkelstein, EIT Spack Consulting
Now that we have an understanding of the available Crash Analysis tools provided by MnDOT (see our previous posts here, here, and here), let’s look into a real-world example of the application of these tools in a corridor crash analysis.
[Check out our Traffic Corner Tuesday – Crash Analysis at Intersections and Corridors video]
The City of Saint Louis Park asked Spack Consulting to complete a crash analysis along the corridor of Minnetonka Boulevard. The limits were the intersection with Highway 169 in the west and the intersection with France Avenue in the east, a distance of about 3.6 miles. Within the corridor crash analysis, individual intersection crash analyses were complete at the following four intersections of interest:
- Minnetonka Boulevard/Texas Avenue
- Minnetonka Boulevard/Louisiana Avenue
- Minnetonka Boulevard/Dakota Avenue
- Minnetonka Boulevard/Ottawa Avenue
These four intersection analyses were requested by the City due to having the largest crash history along the study corridor without any recent improvements.
Starting with the intersections, the necessary characteristics were determined using Google Earth and confirmed with a site visit. MnDOT’s Traffic Mapping Tool provided the daily volumes for each intersection. The Minnesota Crash Mapping Analysis Tool (MnCMAT) was then used to obtain crash data, assuming a 250-foot circle radius at each intersection. These crashes were filtered to remove any not related to the intersection or traffic control device. Combined with the intersection characteristics, the information was entered in the Intersection Green Sheet’s Intersection Safety Screening. Figure 1 shows these characteristics necessary for the crash analysis and the resultant rates and critical index.
As shown, only the intersection of Minnetonka Boulevard with Louisiana Avenue has a critical index above 1.00, the threshold above which identifies potential safety issues. Using the Green Sheet, the calculations were automatically completed.
For the corridor analysis, Minnetonka Boulevard was sub-divided into nine smaller study segments based on ADT, lane number, and median type. Corridor characteristics were again determined using online mapping and confirmed in the field. For this study, the corridor environment and designation remained the same for the length of the corridor. It is worth noting that Segment 8 and Segment 9 are one-way pairs and were analyzed separately. MnDOT Traffic Mapping provided the daily volumes for each segment. The Crash Data inputs were compiled using the segment selector tool in MnCMAT and creating separate Crash Type Summary Reports for Segment 1 through Segment 9.
The Corridor Green Sheets were used for each segment to develop the rates and Critical Index. Similar to the intersection, once the data was input into the Green Sheet cells, the spreadsheet automatically completed the calculations. Because intersection crashes were not removed from the summary report the “Junction Included” tab was toggled to Yes to assure proper analysis was complete.
Figure 2 shows the nine segments analyzed and their characteristics which were used in the Corridor Green Sheet.
By completing this quick crash analysis for the Minnetonka Boulevard corridor and select intersections, it was very apparent where additional analysis and potential improvements may be necessary to improve safety. The City is now using this information to prioritize the upgrades along the corridor and allocate budget for these upgrades to the locations which would benefit most.
Interested in learning more about Crash Analysis? Check out our other articles on this topic:
- Crash Analysis Definitions
- Crash Analysis: Corridor Crash Rates
- Crash Analysis: Intersection Crash Rates
- Traffic Corner Tuesday Webinar: Crash Analysis at Intersections and Corridors
Or signup for our Traffic Corner Tuesday Series. Free 30-minute traffic engineering webinars by traffic engineering experts.