There's a suburb in Carmel, Indiana known as "Roundabout City." With over 100 roundabouts (more than any other city in the US), one particular design has proven to prevent major accidents.
Double-Teardrop Roundabout
Experts from the Insurance Institute for Highway Safety (IIHS) say that the double-teardrop roundabout design (also known as a "dog bone" roundabout") has "slashed injury crashes by 84 percent and reduced all crashes at these location by nearly two-thirds."
According to their analysis, several of these roundabouts had been converted from traffic signal, four-way stop, three-way stop and two-way stop intersections. Research showed that this conversion "resulted in a 47 percent reduction in injury crashes overall, compared with the number the researchers projected would have occurred if roundabouts had not been adopted." In theory, roundabouts reduce crashes because they force drivers to slow down in order to take the tight turns.
These dog bone interchanges are similar to traditional roundabouts. The major difference is that the circle is squashed at the center. This design feature caters to surface roads that intersect high-speed thoroughfares.
Effects on Traffic Flow
Studies also clearly show that roundabouts can also reduce traffic delays by up to 90 percent.
An older IIHS study or three intersections in Kansas, Maryland, and Nevada where roundabouts had replaced stop signs showed that traffic delays were reduced 13 - 23 percent. Another study in New Hampshire, New York, and Washington state where roundabouts had replaced traffic signals or stop signs showed an 89 percent average reduction in traffic delays.
Studies also clearly show that roundabouts can also reduce traffic delays by up to 90 percent.
An older IIHS study or three intersections in Kansas, Maryland, and Nevada where roundabouts had replaced stop signs showed that traffic delays were reduced 13 - 23 percent. Another study in New Hampshire, New York, and Washington state where roundabouts had replaced traffic signals or stop signs showed an 89 percent average reduction in traffic delays.
Environmentally Friendly
According to the Florida Department of Transportation (FDOT), roundabouts:
A study performed by the San Diego County Air Pollution Control District (APCD) found that each roundabout on La Jolla Blvd. in San Diego County estimated to save 20,000 gallons of gas each year, which in turn prevented 10 lbs. of particulate pollution.
According to the Florida Department of Transportation (FDOT), roundabouts:
- Reduce pollution from cars not accelerating/decelerating and idling at traffic signals
- Reduce noise
- Reduce Fuel consumption by up to 30%
- Can be landscaped with native plants and trees
- Require less land than traditional intersections
A study performed by the San Diego County Air Pollution Control District (APCD) found that each roundabout on La Jolla Blvd. in San Diego County estimated to save 20,000 gallons of gas each year, which in turn prevented 10 lbs. of particulate pollution.
Dangers of Roundabouts
In 2019, a 26-year old motorcyclist was killed after hitting the curb of a roundabout in front of the RiverTown community main entrance on State Road 13 in St. John's County. The motorcycle was overturned, and the driver hit the pavement.
There have been other incidences at that same roundabout where vehicles traveling at high speeds at night barrel right through the middle, causing heavy damage to the landscaping.
Referring to a 2005 to 2013 study of fatal roundabout crashes, the Federal Highway Association has concluded:
"Compared to fatal crashes at all intersections, fatal crashes at roundabouts had higher percentages of crashes that occurred during dark light conditions and crashes that involved motorcycles, speeding, impaired driving, and fixed objects. A high percentage (83 percent) of fatal roundabout crashes were single-vehicle crashes.
"Of the 24 impaired driving crashes, the majority (21 crashes) were associated with alcohol
impairment, with the remainder due to medical or drug impairment. Of the 26 speed-involved
crashes, at least two involved vehicles exceeding 100 miles per hour (mph). Many of the
motorcycle crashes at roundabouts involved loss of control and motorcycles striking curbs. Many of the fixed object crashes involved vehicles striking the splitter and central islands of roundabouts, striking curbs and sometimes other fixed objects such as sign posts, light poles, landscaping walls, boulders, and trees. At least 35 of the 39 fixed object crashes involved vehicles striking a curb. Fatal roundabout crashes were less likely to involve pedestrians or bicyclists when compared to fatal intersection crashes."
In 2019, a 26-year old motorcyclist was killed after hitting the curb of a roundabout in front of the RiverTown community main entrance on State Road 13 in St. John's County. The motorcycle was overturned, and the driver hit the pavement.
There have been other incidences at that same roundabout where vehicles traveling at high speeds at night barrel right through the middle, causing heavy damage to the landscaping.
Referring to a 2005 to 2013 study of fatal roundabout crashes, the Federal Highway Association has concluded:
"Compared to fatal crashes at all intersections, fatal crashes at roundabouts had higher percentages of crashes that occurred during dark light conditions and crashes that involved motorcycles, speeding, impaired driving, and fixed objects. A high percentage (83 percent) of fatal roundabout crashes were single-vehicle crashes.
"Of the 24 impaired driving crashes, the majority (21 crashes) were associated with alcohol
impairment, with the remainder due to medical or drug impairment. Of the 26 speed-involved
crashes, at least two involved vehicles exceeding 100 miles per hour (mph). Many of the
motorcycle crashes at roundabouts involved loss of control and motorcycles striking curbs. Many of the fixed object crashes involved vehicles striking the splitter and central islands of roundabouts, striking curbs and sometimes other fixed objects such as sign posts, light poles, landscaping walls, boulders, and trees. At least 35 of the 39 fixed object crashes involved vehicles striking a curb. Fatal roundabout crashes were less likely to involve pedestrians or bicyclists when compared to fatal intersection crashes."
Final Thoughts
Roundabouts may be safer, more efficient, and more environmentally friendly, but accidents still happen. Call Alisa Wilkes, Jacksonville car accident lawyer, if you've been injured in a car accident or collision.
Roundabouts may be safer, more efficient, and more environmentally friendly, but accidents still happen. Call Alisa Wilkes, Jacksonville car accident lawyer, if you've been injured in a car accident or collision.