Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Civil, Construction, and Environmental Engineering

First Advisor

Shauna Hallmark


If transportation agencies are going to move Towards Zero Deaths on their roadways, it will be essential to address the thousands of fatal and injury crashes occurring at intersections. With nearly 3,000 fatalities at rural intersections annually, better intersection designs are critical. Roundabouts are a proven safety countermeasure, but until this point the safety data for rural roundabouts on high speed roadways has been limited. This research conducted an in depth safety and approach speed data analysis for rural roundabouts on high speed roadways and provides the first published planning level crash prediction model available for rural roundabouts.

Crash analysis results showed that rural roundabouts with high speed approaches significantly reduced total crashes by 62 to 68 % and injury crashes by 85 to 88 % at nineteen rural roundabouts. Moreover, the number of angle crashes, which tend to have a higher likelihood of causing injuries at high speeds, were reduced by 83%, also a statistically significant reduction. Approach speed data proved that drivers are able to slow down in advance of roundabouts on rural roadways and the mean speeds at 100 ft from the yield line were 2.5 mph lower than mean speeds at 100 ft from the stop bar at stop controlled approaches. Additionally, a comparison between roundabout approaches with and without rumble strips showed mean speeds 4.3 mph and 3.3 mph lower at 100 ft and 250 ft from the yield line, respectively, for the approaches with rumble strips; however, the variation in speeds increased with the introduction of rumble strips.

The results of this research support decision-making to invest in an intersection alternative that lowers speeds and significantly reduces the risk of injury crashes. Roundabouts eradicate the risk of drivers running stop signs and red lights. Roundabouts save lives.


Copyright Owner

Hillary Isebrands



Date Available


File Format


File Size

193 pages