CASE STUDY LOCAL
CASE STUDY NATIONAL
As of 2019 the City contains more than 125 roundabouts. Due to the development of all these round-a-bouts, the city has seen a reduction of crashes that result in injury by 80 percent and a total reduction in crashes by 40 percent at locations where round-abouts are implemented. A study indicated that in 1996 the average number of accidents averaged to roughly 7 injuries for every 1,000 residents. This number has decreased by 2017 with 2 injuries for every 1,000 residents (data extrapolated to cover the year after analyzing 15 days of traffic accidents). This decrease in accidents has occurred even with an increase in population from 31,808 in 1996 to 92,475 in 2017.
As a result, all intersections saw either a decrease in fatal crashes or remained the same over this observation period. Injury related crashes also decreased by 79 percent or higher at all intersections. Two intersections did see a slight increase in total crashes (one or two more than what was counted during the before installation study), but otherwise the results remain positive for decreasing the total number of collisions. Overall, total crashes decrease 69 percent, injury related crashes decreased 88 percent, and fatal crashes decreased 100 percent.
Carmel, Indiana is one of the most well-known communities that have implemented round-a-bouts in their community. The questions is, are these traffic improvements providing the benefit they were intended for? Carmel has replaced a significant number of its signalized intersections with roundabouts since 1996 in the hopes to save money for the city and its motorists while reducing traffic incidents.
Maryland state conducted a study at five different locations where round-a-bouts were installed. Each of these round-abouts were installed at intersections that were originally twoway stop-controlled intersections that saw high collisions. The study examines the crash data prior to and after round-a-bout conversion at these sites over a 15-year period (1990-2007) but the observation periods ranged between five to 13 years.
Overall, Maryland did not experience implementation issues with installation of the round-a-bouts. Average costs during this time ranged from $194,000 to roughly $500,000 per round-a-bout depending on the location.
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