For many queries it is important to define what is an intersected related collision and the definition can vary from agency to agency. A section is now available to explicitly define these collisions by setting specific attributes. In the High Collision Intersections, Intersection History, Corridor Query or High Collision Segments queries the Define Intersection Related Collision section is available. There are several options that are based on fields formerly included as collision filters. The options include:
- Distance From Intersection
- For All collisions
- For rear-end collisions on approach
- At Intersection indicator
The default distances are for all collisions <= 50 feet and for rear-end collisions on approach <= 150 feet. This means that between 51 and 150 feet if it is a rear-end collision, it will only be designated as intersection related if the parties are traveling towards the intersection. If they were traveling away from the intersection it is unlikely intersection related and would be excluded. Within 50 feet of the intersection any collision type or direction of travel are included as intersection related collisions.
The At Intersection field refers to the officer indicated field on the collision report and can be used as an additional restriction to define intersected related collisions. For example, it is possible that two collisions that are 15 feet from the intersection are marked differently by the officer for being At Intersection. Using simply distances, both would be defined as intersection related and included in the query. However, if you check the At Intersection checkbox, it will only include the collision that is marked At Intersection. The use of the At Intersection field varies widely in collision data by officer or agency and distance is commonly the only used specification for intersection related queries.
For corridor queries, it will now incorporate the specified filters from Define Intersection Related Collisions when choosing to include or exclude start, end or intermediate intersections and no longer require separately specifying a distance from intersection. For more information refer to the corridor queries help page.
For General Queries or Spatial Queries, the Define Intersection Related Collisions section is not available and the collision filters should be used as highlighted in red below. Note that since these are systemwide queries not specifically focused on intersections, the rear-end distance filter will not take into account any approach direction and will simply include or exclude all rear-end collisions within the distance specified.