This story is part of The Salt Lake Tribune’s ongoing commitment to identify solutions to Utah’s biggest challenges through the work of the Innovation Lab.
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Roundabouts, whether you love them or hate them, could be a small way to reduce tailpipe emissions.
Though they slow down individual drivers, roundabouts hardly ever stop traffic, meaning cars aren’t left idling – and polluting – at intersections.
“Queues tend to be short and fleeting at modern roundabouts,” said Ken Sides, chairperson of the Institute of Transportation Engineers’ roundabout committee and an engineer at Sam Schwartz Engineering, “thus the emissions of toxic fumes are reduced.”
The federal Department of Transportation reports that emissions in roundabouts were lower than at intersections with stop lights with fixed time intervals, even with high-traffic volumes.
Salt Lake City has constructed more roundabouts in recent years, including at 1100 East and 900 South and at 2100 South and Interstate 80, but the goal hasn’t been to reduce emissions, Jon Larsen, director of the city’s Transportation Division, said.
“We spend more time and effort on more transformative” means of transportation to reduce emissions, Larsen said, including making streets more friendly to pedestrians and cyclists.
To have a serious impact on emissions, Salt Lake City would need to start converting busy intersections – where lines of cars wait idling – into roundabouts. Because of the “expectations and capabilities” of American drivers, Larsen said he isn’t looking at roundabouts any more complicated than one or two lanes for the city.
Replacing traditionally lighted intersections in downtown areas is difficult too, said Sides, who regularly visits Utah to ski, because existing buildings take up some of the needed space for the larger infrastructure projects.
Even though Salt Lake City isn’t going to become a leader in roundabouts anytime soon, Larsen said the city does still plan to build more of them – a plan that could come with some serious pushback.
“There are people who are very pro roundabouts,” Larsen said, “and people who are really against them.”
About two-thirds of residents typically oppose roundabouts when they’re proposed, Sides said, but once construction is completed, about two-thirds of residents prefer them, he said.
Roundabout near 9th and 9th
Intersections where more than two streets converge can be difficult to navigate, making them candidates for a roundabout. For example 900 South and 1100 East also intersect with Gilmer Street, making a complicated five-point intersection.
(Trent Nelson | The Salt Lake Tribune) The roundabout at 900 South 1100 East in Salt Lake City on Monday, Dec. 13, 2021.
“There weren’t a lot of elegant solutions there other than a roundabout,” Larsen said.
That roundabout, as well as others in the city, also provides some green space and features public art, though the “Out of the Blue” sculpture planned there has proven controversial among residents.
Bridget Geyer, owner of The Bridal Studio at 1085 E. 900 South is one of the sculpture’s opponents. Not because she doesn’t like art, she said, but because she thinks the 40-foot whale tail will further obstruct the view of drivers entering the roundabout.
The roundabout is better than the complicated intersection that existed before, she said, but she sees many close-calls each day as drivers almost crash.
“They help the flow of traffic,” Geyer said of roundabouts, “but I don’t know if they teach about them in driver’s ed. here.”
“Obviously, people don’t know how to use them,” she said.
Safety
Roundabouts are still fairly rare in the U.S. – especially compared to countries like France and Australia – so some drivers still have difficulty approaching them.
Even though engineers report more fender-bender crashes in roundabouts, crashes in roundabouts are typically far less serious than at lighted intersections.
Instead of right-angle or T-bone collisions in an intersection, vehicles will typically hit others in a roundabout at a 45 degree angle that could glance off a car rather than stop one in its tracks.
“There is an enormous lost opportunity to reduce fatal crashes at intersections,” Sides said.
Speed is another important factor in crashes. With vehicles driving around a bend, high-speed collisions are less likely in. roundabout.
Lighted intersections replaced by roundabouts reduced crashes with fatalities and injuries by 78% on average, according to the Federal Highway Administration. Intersections with two-way stops replaced with roundabouts saw crashes reduced by 82%.
(Rick Egan | The Salt Lake Tribune) This roundabout connects 2300 East, Vimont Avenue and I-80 in Salt Lake City.
“There is really no other transportation project that a transportation engineer can work on that will save more lives,” Sides said.
Older roundabouts can be more difficult or uncomfortable for pedestrians or cyclists to cross, Larsen said, but the city puts an emphasis on designing roundabouts that have safe crossings.
How to drive in a roundabout:
Slow down when approaching;
Yield or stop for pedestrians or cyclists crossing;
Merge into the roundabout;
Signal your exit from the roundabout for two seconds.
