If Sacramento adds roundabouts, they could curb fatal crashes and fender benders. Here’s how
Sacramento has the worst traffic fatality and injury rate among large California cities, and city officials are considering a roundabout pilot project to see how they would work here.
Roundabouts almost halved traffic collisions at intersections across Carmel, Indiana, and reduced injury crashes by 80%.
They achieve their safety improvements through a few key factors.
Roundabouts slow traffic down
Speed demons won’t like hearing this, but faster speeds lead to more dangerous crashes. The Federal Highway Administration says the curvature of a modern roundabout will force drivers to slow to speeds between 15 mph and 25 mph. The United Nations and the World Health Organization have said that 20 mph should be the “maximum speed limit” for urban centers where drivers frequently share space with road users who are not in cars, such as pedestrians and cyclists.
The risk to pedestrians and other vulnerable road users rises alarmingly at speeds over 20 mph. A study in the public health journal Accident Analysis & Prevention found that if a driver hits a pedestrian at 24.1 mph, the average risk that the pedestrian will die is already 10%; if the driver is traveling at 40.6 mph, the risk that the pedestrian will die is 50%.
The city has reported that 78% of crashes happen at intersections; roundabouts slow drivers down in the places where crashes are most likely to happen. So, when collisions do occur in roundabouts, they typically aren’t very dangerous because the cars are going relatively slowly.
Roundabouts reduce how much you need to pay attention to
For everyone using a roundabout — drivers, pedestrians, cyclists — there’s less to look for compared to a traditional four-way intersection.
All vehicles are traveling in one counterclockwise direction. The roundabouts eliminate left turns, so there’s no checking oncoming traffic and checking for pedestrians and cyclists in the crosswalk a driver is about to turn into. They remove a lot of opportunities for error.
Roundabouts eliminate dangerous left turns
When you are using a roundabout, you simply aren’t going to turn left. That eliminates a lot of risk. Because a left turn can be made at a wider angle than a standard right turn, drivers can move at higher and thus more dangerous speeds. They have more to pay attention to. In most cases, they are putting their vehicle into an oncoming lane of traffic, and, if they misjudge, they could be involved in a broadside crash.
Left turns are also especially dangerous for people outside cars. In New York City, the Department of Transportation compared left turn crashes and right turn crashes and found that pedestrians and cyclists were killed or seriously injured by left turns at a rate three times higher than they were by right turns.
So, by turning every would-be left into a loop, the roundabout cuts out a lot of opportunities for collisions.
Roundabouts stop people from racing to beat a red light
The classic roundabout does not have signals. This means that no one takes the risk of speeding up to make a red light because there are no red lights.
On the contrary, the roundabout forces drivers to slow down before entering the intersection.
Roundabouts keep traffic flowing, though at a slow pace — and they cut pollution
Because a standard roundabout has a “yield” for all points of entry, the intersection design cuts down on congestion. Jeremy Kashman, the chief infrastructure officer of Carmel, Indiana, said his city had calculated the benefits of their network of around 150 roundabouts.
“We’re probably saving over 300 tankers of fuel a year in just the efficiency of our network and lack of idling,” he said. “It’s over 50,000 pounds of carbon dioxide.”
This story was originally published August 22, 2024 at 5:00 AM.
