If Turns are Dangerous to Make while Driving, What is the Solution?
Where I live the roads are typically 4 lanes, or two each way, and have an island in the middle. The speed limit is set at 45 mph which I have stated time and time again, it is merely a suggestion. People are going well over 45 mph which makes it more dangerous to make turns. The enforcement is weak also.
So. banning left turns sound good. How would you go the other way if needed?
“Here’s a way to save lives, curb traffic jams and make commutes faster and easier − ban left turns at intersections,” The Conversation
Vikash Gayah: When you make a left turn, you have to cross oncoming traffic. When you have a green light, you need to wait for a gap in the oncoming traffic before turning left. If you misjudge when you decide to turn, you could hit the oncoming traffic, or be hit by it. That’s an angle crash, one of the most dangerous types of crashes.
Also, the driver of the left-turning vehicle is typically looking at oncoming traffic. But pedestrians may be crossing the street they’re turning on to. Often the driver doesn’t see the pedestrians, and that too can cause a serious accident.
On the other hand, right turns require merging into traffic, but they’re not conflicting directly with traffic. So right turns are much, much safer than left turns.
What are the statistics on the unique dangers of left turns?
Gayah: Approximately 40% of all crashes occur at intersections − 50% of those crashes involve a serious injury, and 20% involve a fatality.
About 61% of the crashes at intersections involve a left turn. Left-hand turns are generally the least frequent movement at an intersection, so that 61% is a lot.
Why are left turns inefficient for traffic flow?
Gayah: When left-turning vehicles are waiting for the gap, they can block other lanes from moving, particularly when several vehicles are waiting to turn left.
Instead of the solid green light, many intersections use the green arrow to let left-turning vehicles move. But to do that, all other movements at the intersection have to stop. Stopping all other traffic just to serve a few left turns makes the intersection less efficient.
Also, every time you move to another “phase” of traffic – like the green arrow – the intersection has a brief period of time when all the lights are red. Traffic engineers call that an all-red time, and that’s when the intersection is not serving any vehicles. All-red time is two to three seconds per phase change, and that wasted time adds up quickly to further make the intersection less efficient.
What restrictions have been tried in different cities?
Gayah: When a downtown is not very busy – in the off-peak periods – allowing left turns is fine because you don’t need that additional ability to move vehicles at each intersection.
Some cities are implementing signs that say no left turns at intersections from 7 to 9, which is the morning peak period, or 4 to 6, which is the afternoon peak period. In San Francisco, for example, Van Ness Avenue restricts left turns during peak periods.
But cities aren’t implementing these restrictions on a larger scale. Restrictions are more along individual corridors or isolated intersections instead of essentially the entire downtown, where possible. That would make the downtown street network more efficient.
Roundabouts are one approach to avoiding left turns.
Gayah: Roundabouts are safe because there’s no longer a need to cross opposing traffic. Everyone circulates in the same direction. You find where you need to go and then exit.
But restricting left turns, in general, is more efficient. Roundabouts aren’t as efficient when it’s busier. The roundabout gets full, which can cause a gridlock, and no vehicle can move. Traditional intersections are less prone to gridlock.
Roundabouts also take up more space. Installing a roundabout might mean expanding the intersection. In some downtowns, that means tearing down buildings or removing sidewalks. Restricting left turns only requires a sign that says “no left turns” or “no left turns during peak periods.” That’s it.
What are the benefits to banning left turns in urban areas?
Gayah: Any way you cut it, eliminating left turns will result in longer travel distances. I’ll have to travel a longer distance to get to where I need to go. The worst case is having to circle the block. I’m actually traveling four extra block lengths to get to where I need to go.
But not all trips require circling the block. In a typical downtown, each trip will be about one block length longer on average. That’s not a lot of extra distance. And that extra driving is more than offset by the fact that each intersection with banned left turns is now moving more vehicles. Which means every time you’re at an intersection, you wait less time, on average. So you travel a slightly longer distance but get to where you’re going more quickly.
Does avoiding left turns improve fuel efficiency?
Gayah: Our research found that even though vehicles travel longer distances on average with the restricted left turns, they spend less fuel – about 10% to 15% less per trip – because they don’t stop as much at intersections.
This is why UPS and other fleets route their vehicles to avoid left turns. There’s less idling and fewer stops.
Do you think banning left turns could become widely accepted?
Gayah: It’s a new strategy, so it’s uncomfortable for some people. But when they get to their destination faster, I think people will latch onto it.
Streets and roads have a “natural” speed limit. This is my observation. I do not have data.
Drivers drive the speed they feel comfortable with.
4 lanes with an island feels like a superhighway.
@Dave,
“Drivers drive the speed they feel comfortable with.”
LOL! And every single time I’ve gotten a speeding ticket, I was driving the speed I was comfortable with*. Guess I shoulda told the officer that. He didn’t seem aware of the herd speed limit policy.
I also got a traffic ticket for failing to come to a complete stop before making a right turn on red with no traffic early on a Sunday morning. I was totally comfortable with that act, but the red light camera won.
*my first speeding ticket was for driving 120 mph in a 75 mph zone. I was 17 and totally comfortable in the Pontiac LeMans 400 I was driving.
Dave:
If it is one contiguous road or a highway, you could be correct. This is not and there are many sideroads coming into it from neighborhoods. Speeding at faster speed does not allow a safe entry to the road.
As I pointed out for an over used 4 lane highway 14 miles long before it joins another. If you go 65 mph, it will take ~13 minutes. If you go 75 mph, it will take ~11.2 minutes. There is no safe reason to exceed the speed limit by a lot. Plus it becomes a safety factor as your reaction time is less as well as stopping ability taking longer and people do not give adequate distance.
Natural is in your mind and not a reality when there are multiple variables to the same road.
Do you really trust people’s belief that they are competent to drive at what they consider a “natural” speed limit? I don’t; I especially don’t trust the post-pandemic driving that I see whenever I drive myself. Moreover, faster speeds increase damage to the roadway, resulting in more frequent road resurfacing – great for paving contractors, not great for tax payers or drivers. Plus with the battleships that people are driving these days, roads deteriorate even faster (roughly as the 4th power of the weight of the vehicle). And those battleships are very perilous to pedestrians, especially kids, as well as to drivers in smaller vehicles.
Don’t trust your gut feelings. Don’t be like Donny.
@Bob,
Well said.
Bob:
Good to see you, And thanks for the comment.
Roundabouts get full???
not when they have priority.
Many US towns use 4 lanes with intersections where 2 lanes with roundabouts would have enough capacity.
examples in Carmel, indiana.
He has never been trapped on 57th Street in Manhattan trying to head west but being forced east and farther east as one crosses avenue after avenue where one can turn neither left or right. Out where I live now, the solution is roundabouts. They work fairly well for country driving, but you have to slow to 15-20 mph which is also inefficient. Australia uses s lot of roundabouts in rural areas, and my introduction to navigating England was “go round the roundabout” back in the 1960s. Massachusetts took it to a new level when they changed who had the right of way at roundabouts and everyone just gave up and to this day consider it a scrum.
Making a left turn has been a challenge since way when. Edgar Rice Burroughs has one of his characters in his Mars books explain, to the Earth reader, how Martians manage to avoid left turns in their air cars by having the left lane fly up and over. We still don’t have flying cars. Maybe if we colonize Mars.
@Kaleberg,
” . . . but you have to slow to 15-20 mph which is also inefficient.”
I slow to 0 mph at a red light and idle till it turns green. That’s inefficient. Merely slowing to 15-20 mph is more efficient, IMO.
Yes, a crowded traffic circle can cause a back-up. I can’t count the times I’ve had to wait two or three cycles to get through an intersection with a traffic light. The problem isn’t the traffic circle, it’s the traffic.