Write Up:

Interstates connect the nation and keep people and commerce flowing. When interstates shut down in Missouri, the country is cut in half. Keeping interstates flowing is a top priority for MoDOT, but sometimes unplanned incidents affect the department’s ability to keep the interstates moving. An unplanned incident can be related to weather, emergency road repairs, traffic crashes or other incidents. 

Of the types of unplanned incidents that can occur, traffic crashes create most of the impacts. Using the nationally adopted Highway Safety Manual, an expected crash number is established for each direction of I-70 and I-44 per county. The expected crash number is determined by the traffic volume, roadway characteristics (e.g. number of lanes, lane width, shoulder width, roadway alignment, etc.), calibration factors to local conditions and reported crash data over a five-year period. The expected crash number provides a glimpse into the number of crashes one could expect to occur and help identify opportunities for improvement. When the number of observed, real-world crashes is higher than the expected crash number, this could indicate an opportunity for enhancements to reduce the frequency of crashes. Identifying these locations can help the department prioritize locations for improvements.  

In most counties, the interstates have a safety performance similar to what is expected. However, there are some counties where there may be opportunity to reduce the frequency of crash incidents, such as along I-44 in Pulaski, Phelps and Franklin counties. There have also been instances of success in reducing crash incidents, such as I-70 westbound in St. Charles County.

It should be noted that crashes overall in Missouri were lower in 2020 compared to previous years due to reduced travel associated with the pandemic.  However, for this measure, the observed crash data is reported in five-year averages, minimizing the influence of this unique event.

Purpose of the Measure:

Measure the crash performance of I-44 and I-70 utilizing national analytical standards in order to identify locations which have an opportunity for positive change.

Measurement and Data Collection:

The limits of the interstates analyzed are as follows:

I-44: Oklahoma State Line to Route 100 in Gray Summit

I-70:  Route 7 in Blue Springs to Route Z in Wentzville

Observed crashes are pulled from MoDOT's Transportation Management System and represent all reported crashes which occurred between the limits on each interstate. The miles used to determine the crash per mile are also pulled from MoDOT's Transportation Management System. Expected crash per year per mile numbers were calculated using the ISATE spreadsheets developed with the American Association State Highway Transportation Officials  Highway Safety Manual.