We Should Abolish the Left Turn, Science Suggests
Researchers say that outlawing some left turns will improve traffic.
Lots of car crashes happen because of left turns in busy intersections.
Many cities already have restrictions on some left turns.
It might be time to give up your wild Waze: New research suggests eliminating at least some left turns will make roads a lot safer.
For drivers in the U.S., turning left is one of the most dangerous moves on the road; approximately 61 percent of all crashes that take place at intersections involve a left-hand turn.
Why? Because left turns take you against traffic and in the path of oncoming cars, and most take place at drivers’ discretion, not during the distressingly brief left-hand arrow at busy intersections. This has caused some experts to say yellow lights need to be longer in order to conform to safety guidelines, for example.
But that’s a long way from this new research, where scientists from Penn State University say eliminating left turns is a smart idea for safety’s sake. In a new paper appearing in Transportation Research Record, they try to strike the right balance between strategically eliminating left turns in some locations without putting too much of a burden on drivers to travel a lot farther.
So, how does driving work without left turns? You just plan ahead a bit more and take right turns that eventually lead back to your original location. Some cities, like San Francisco, Salt Lake City, and Wilmington, Delaware have already limited left turns.
Consider this extremely scientific diagram:
If it looks a little bit like a highway cloverleaf interchange, that’s not surprising. Highway cloverleafs are one of the most well-designed ways to introduce turning drivers back into the flow of traffic safely, with just a little bit of merging stress instead of left turn surprises of any kind. Turning right is easier, safer, and potentially quicker compared to the wait to turn left.
Let’s really think this through, though. Does it work better?
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Here’s a scenario that exposes one of the limitations of eliminating left turns. What if a driver takes the longer route above to make three right turns instead of one left, and now they must drive straight across a hypothetically busy street? If there’s not a light at the intersection, there’s more danger in trying to cross all the way through the street instead of just turning left.
It’s clear that getting rid of left turns isn’t a one-size-fits-all solution, which is why this research focuses on finding the right balance between fewer and more left turns. In their study, the Penn State researchers used three algorithms on both perfect and imperfect grids, where imperfect grids are more like the real-life cities where people are driving.
Lead study author Vikash Gayah, a transportation engineering professor at Penn State, says his research team’s results follow a broad theme. “Left-turn restrictions are more effective at busier intersections in the centers of towns or cities than at less busy intersections farther from the town center,” Gayah writes in The Conversation.
This makes sense, because more people are affected at busy intersections. Gayah says more urban drivers also have more options for alternate routes, making the extra turns more negligible.
There’s one interesting complication: “[F]ewer cars tend to turn left at these central intersections to begin with, so the negative impact of removing left turns is relatively small,” Gayah explains.
That might suggest people are already wising up to the idea that left turns can be brutal and should be avoided.
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