Study shows two-lane roundabouts reduce crash risk

Whether it's due to a motorist who stops short all of a sudden or an anticipated four-way stop, braking systems found in passenger vehicles and trucks help make the roads safer by preventing crashes and turning potentially serious accidents into mere fender-benders.

Highway safety officials aim to keep speeds low and braking under control through the strategic use of roundabouts, or rotaries, as they're more commonly referred to in the New England area. These have proven effective in reducing congestion by keeping the roads moving without the constant stop-and-go traffic associated with intersections.

However, as two-lane roundabouts become increasingly common to cut down on heavy volume during rush hours, there's some question as to whether they're actually helping the roads stay safer or hindering it due to their complexity. According to a recent study from the Insurance Institute for Highway Safety, it's the former.

Examined 127 rotaries nationwide
IIHS came to this conclusion after examining traffic volume in both single-lane and two-lane roundabouts between 2009 and 2015. Of the 127 rotaries involved in the study, 98 were single-lane and 29 were two. From a sheer numbers perspective, there are more single-lane roundabouts in the U.S., thus the disparity in analysis.

After controlling for certain contributing factors that affected volume, the researchers found that over the course of the study period, crash incidents rose 7% at single-lane roundabouts but the chances of injury fell substantially, down 19% on an annual basis.

"The crash average in these roundabouts fell 9% on average per year between 2009 and 2015."

Because two-lane rotaries can appear difficult to navigate, conventional wisdom might suggest that motorists may apply the brakes errantly while coursing through them, thus resulting in a rear-end accident. In reality, the crash average in these roundabouts fell 9% on average per year between 2009 and 2015 and the potential for a severe injury dropped 33% annually.

Wen Hu, the study's lead author and senior research transportation engineer at IIHS, said he attributes the decreasing rate of accidents to motorists becoming more skilled at when to apply the brakes as they grow more accustomed to using two-lane rotaries.

"Two-lane roundabouts are inherently more complex than the single-lane type," Hu explained. "Even in a place like Washington, many drivers still aren't familiar with them, so it makes sense that there would be more crashes when a roundabout is first built than after it has been in place for a while."

Perhaps the biggest advantage to rotaries, aside from their ability to keep the roads moving when volume picks up, is they're proven to reduce the types of crashes that are typically the most serious in terms of potential for injury. According to the IIHS, head-on, right-angle and left-turn collisions are the accidents that are most likely to result in one more injuries, potentially life threatening.

Wisconsin uses most roundabouts per capita
Roundabouts were practically non-existent in the 1980s, despite their ubiquity throughout much of Europe at this time. They're much more common today, however, with Wisconsin averaging the most in the U.S. on a per capita basis at 7.9 per 100,000 licensed drivers, Bloomberg reported. Alaska, North Dakota, Kansas and Colorado round out the top five.

Traffic infrastructure and roadways designed to keep speeds low are immaterial without high performing braking systems. Contact Greening Associates for a complimentary consultation to ensure they're in good working order and stay that way.