4 types of crashes lead to traffic fatalities
56% of crash fatalities nationally were frontal collisions,
24% were right angle collisions,
6% were rear end collisions and
14% were other types of crashes (single vehicle/rollovers/etc.).
Source: Insurance Institute for Highway Safety, 2017
Roundabouts are not a cure-all.
Whether a crash leads to a fatality in a given case depends on human factors that can’t be controlled by engineering design alone, including the use of seat belts, impaired driving, type/size of vehicles involved, distracted driving, age/health of vehicle occupants, etc.
What roundabouts excel at is:
the types of crashes
that occur at an intersection
Frontal collisions (head-on, left-turn)
are practically eliminated.
are greatly reduced and occur at lower speeds
with less severe angles.
are reduced and occur at lower speeds.
Low speed merging/swiping collisions
may or may not increase slightly (taking the place of the more severe types of crashes), but the angle of impact leads to fewer serious injuries compared to frontal, right-angle and rear-end crashes.
In addition to improving safety, roundabouts also:
Improve traffic flow
For example, studies by Kansas State and the Insurance Institute have found a 20% to 89% reduction in delays at roundabouts.
Simplify complex intersections
For example, when multiple roadways of different capacity merge, or when streets merge at unusual angles due to geography or existing infrastructure.
Functional During Power Outages
During power outages, the roundabout functions normally compared to signalized intersections.
Less acceleration and braking reduces noise pollution.
Better fuel efficiency and reduced greenhouse emissions also results
from less acceleration and braking.
MoDOT: All About a Roundabout (Video)
IIHS: How Roundabouts Work (Video)
Mini Roundabouts (Video)