This article will walk you through how to generate a Left Turn Crash Report. This report can be used by Traffic Engineers to identify left-turn crash trends at study intersections to confirm if a change in left-turn phasing is justified.
This template can be used to generate a list of turning movement counts, grouped by movement, and year.
How to Generate a Left Turn Crash report
1. Login to gdot.numetric.com
2. In the Crash Query application, click on the Home icon (located to the right of the Crash Query dropdown in the top left corner of the screen).
3. From the Saved Queries window, select the Left Turn Crash Analysis TEMPLATE query, under the GDOT Templates category. (You can also open the template directly from this link - you may want to copy and paste this link in your browser, then bookmark, or flag it as a favorite site to make future access easier)
4. With the Left Turn Crash Analysis Template query open, click the Make A Copy icon, located in the top right corner of the screen (two stacked squares).
5. In the Save Crash Query window, name the query, and change the Category in the dropdown to Traffic Engineers, and click the Save button.
6. Adjust the date range for your query by modifying the Date Extents, located in the top right of the screen.
Then select the desired date range to evaluate from the Date Extents screen.
7. From your new query, apply a polygon filter around the intersection you would like to analyze. Remember to save your query after applying filters, otherwise your changes will not be saved.
NOTE: When drawing the polygon filter around your selected intersection, be careful to not include any driveways in the polygon. Crashes occurring in a driveway should not be included in the report, and may skew your results. Additionally - you can use the Radius Filter (the icon directly under the Polygon Tool) to mark out an intersection)
8. Click on the Chart Builder tab, and download the pivot table titled Left vs Straight Opposing Movement Crashes. This will download a CSV of left turn crashes grouped by turning movement, and year (Note: You may also download the Left vs Straight Opposing Movement Crashes, and Left Turn vs Straight Opposing Movement by Hour of Day charts).
9. Change the name of the recently downloaded CSV to include the name of the intersection included in the report.
10. You now have a downloaded Turning Movement Count spreadsheet. Use this spreadsheet to determine and justify any phasing changes.
Note: If you decide not to utilize the Left Turn Crash Analysis Template query as a starting point for your report, you can add the Left vs Straight Opposing Movement Crashes T/F = Yes filter to a new query, then create your own Left vs Straight Opposing Movement Crashes chart by selecting the Pivot Table chart type, Collisions Dataset (Count) Measure, Left vs Straight Opposing Movement Grouping (rows), and Date and Time (Year) Grouping (columns).
Additionally - you can use the screenshot, or snipping tool to capture a screenshot of the map and charts to paste the images into the Traffic Engineering Document.