According to a recent study by the Insurance Institute for Highway Safety, an unusual type of roundabout has provided significant advantages to the Indianapolis suburb called “Roundabout City.”
According to the IIHS, the double-teardrop design implemented by Carmel, Indiana, along Keystone Parkway and other busy crossings decreased injury crashes by 84 percent and overall collisions by nearly two-thirds. The double-teardrop interchanges and more traditional roundabouts together reduced injury accidents by half.
Keep reading to learn why this specific design worked and then contact Law Offices of Fernando D. Vargas at 909-982-0707 if you have been injured in a car accident and require a legal consultation.
Carmel, Indiana Has More Roundabouts Than Any City in the Country
With almost 100 roundabouts, Carmel has more than any other city in the United States. Even though the city’s population has risen from approximately 25,000 people in the 1990s to almost 100,000 people now, Mayor James Brainard credits them with lowering pollutants, improving traffic flow, and keeping collision statistics low.
How the Data Was Crunched
IIHS researchers looked at collision data from 64 roundabouts for two years before and after they were built to see how much they influenced road safety. They compared collision counts from each modified intersection to a conventional intersection with similar features nearby since data on previous traffic levels was not available.
Between 2005 and 2017, the sample comprised 21 single-lane, ten double-teardrop, and 33 different multilane roundabouts. Before the conversion, traffic signals controlled 25 of the junctions, 19 of which were four-way stops, four of which were three-way stops, and 16 of which were two-way stops.
According to the IIHS, the conversion to roundabouts resulted in a 47 percent reduction in injury collisions overall, compared to the number predicted by the researchers if roundabouts had not been implemented.
The Difference Between Single- and Multi-Lane Roundabouts
Multilane roundabouts were linked to increases in total collisions and property-damage-only accidents, whereas single-lane roundabouts were linked to increases in total crashes and property-damage-only crashes. Single-lane roundabouts had a 50% reduction in injury collisions, while multilane roundabouts saw a 15% reduction, however these figures were not statistically significant.
The double-teardrop roundabouts had a more dramatic effect. Injury crashes decreased by 84 percent and overall collisions decreased by 63 percent in places where that design was implemented, according to the study.
Roundabouts minimize collisions, particularly injury crashes, by forcing vehicles to slow down due to the circular median and narrow turning radius. Because cars are no longer crossing perpendicularly, the most severe forms of junction crashes — right-angle, left-turn, and head-on collisions — are also rare.
Of course, nothing can prevent 100% of accidents. If you are involved in a car accident and require a free legal consultation, call Law Offices of Fernando D. Vargas at 909-982-0707.
