see also - How to Create a Crash Tree Diagram.

Crash Tree Diagrams can help users identify where crashes occur, what kind of roadway attributes correlate with crashes, or what kind of behavioral elements correlate with crashes. With this information, a city, county, or state, can make informed decisions regarding potential safety improvements on their roadways.

A Crash Tree Diagram is a visual representation of crash data, where each branch represents a more detailed breakdown of crash characteristics - sort of like a family tree of crash statistics. As you select a crash or roadway characteristic, the tree expands to show you the crash distribution within the selected characteristic. As you continue to add more and more levels, you get a more detailed breakdown of what are the leading attributes of crashes in your study area.

For example, in the Crash Tree Diagram below, we started by looking at the crashes in District 1. As we progress down the tree, we can see the selected branches and the corresponding crash data.

As you can see, Crash Tree Diagrams can be used to identify key crash types and key locations to evaluate for potential safety improvement.

When creating Crash Tree Diagrams, there is no wrong way to explore the data, but there are some best practices that can help find meaningful results.

Start with high-level data points around geographic and roadway features, and add others to explore areas of interest.

Common high-level data points for building Crash Tree Diagrams include:

You may then want to create Crash Tree Diagrams for exploring more detailed data points for specific emphasis areas. Below are several emphasis areas and potential data points to explore:

To learn more about how to build a Crash Tree Diagram, see the How to Create a Crash Tree Diagram article.