It is important to specify filters for intersection related collisions, especially when generating intersection histories or high collision intersection lists. Typically one might want to include only collisions that occurred directly at an intersection, but other times any collisions within 50 feet might be valid to include. Therefore, there are several different ways to specify which collisions to include based on your needs. Let’s take a look at an example case using data from the San Francisco demo set to walk through different scenarios.
The screenshot below shows the results of an intersection history query without any filters set for Duboce Ave and Valencia St between 1/1/11 and 12/31/11. There are 11 collisions in the results, which means that in the entire database all these collisions were marked as occurring at or near this intersection. However, this includes all collisions regardless of how far from the intersection they occurred. Looking at the Dist (ft) field, you can see 4 of the collisions have a non-zero value.
By switching over to the map view it is easy to see how they are distributed near the intersection.
If you wanted to exclude any of those 4 collisions not directly at the intersection, there are two different filter options.
In the collision related filters, click the drop down for Intersection Related filter and select Intersection. Only collisions with a distance from intersection of 0 will be shown in the results.
Or in the collision related filters, click the drop down for Distance From Intersection filter, select the mathematical symbol (<=). Then enter a distance in feet. Only collisions within this distance will be shown in the results.
Note that both options can be used to specify collisions directly in the intersection (distance = 0).
If you specified Intersection Related = Intersection, the example query will only show the 7 results. If you specified a distance <=, only distances within the range will show in the results.
Collisions at the intersection: