TRAFFIC SAFETY ON RURAL EXPRESSWAYS

This report analyzes a database created from 644 two-way, stop-controlled intersections on rural Iowa expressway highways. Expressways are divided multi-lane highways with a median. This database included five ears of crash data and data relating to the approach traffic volumes and a few geometric features at the intersections. Since the data are from rural intersections, the traffic volumes at many of the intersections are very low and over the five-year period roughly half the intersections experienced no crashes. The author's analysis showed that increasing minor roadway volume results in increasing crash rates and increasing crash severity. Increasing minor volumes also resulted in an increasing involvement of right angle crashes. Although we know that major roadway volumes increase the frequency of crashes, increases in minor roadway volume appear to be more highly related to crash rate increases and increased crash severity. When crash experience at rural expressway intersections is compared to crash experience on all rural intersections with a primary roadway (including expressways), the older drivers (drivers 65 years and older) are found to be over-represented. When the author made comparisons of the type of crashes, right angle crashes at expressway intersections are generally over-represented in most age groups but older drivers are more frequently involved in right angle crashes at all rural intersections, but particularly over-represented at expressway intersections.