From the lower risk of accidents to fuel savings, there are urbanism specialists who point to several advantages in reducing left turns.
More than 60% of traffic collisions In intersections involve left turns. Some US cities – including San Francisco, Salt Lake City and Birmingham in Alabama – are restricting left turns.
Dr. Vikash Gayah, professor of Civil Engineering at Pennsylvania State University and interim director at the Larson Transport Institute, discusses how the left turns at intersections cause accidents, worse traffic and consume more fuel.
How dangerous are the turns on the left at intersections?
Vikash gayah: When making a turn on the left, it is necessary to cross traffic to the opposite direction. When the signal is green, it is necessary to wait for a breach in traffic in the opposite direction before turning left. Calculating poorly when deciding to turn, it can collide with traffic in the opposite direction or be hit by it. This is an angle accident, one of the most dangerous types of accidents.
In addition, the driver of the vehicle that is going to the left is usually the look at traffic to the opposite direction. But pedestrians may be crossing the street to which they are turning. Often the driver does not see the pedestrians, and this can also cause a serious accident.
On the other hand, turns on the right require integration in traffic, but do not go into a direct conflict with traffic. Therefore, the turns on the right are much, much safer than the turns on the left.
What are the statistics on the specific dangers of left turns?
Concern: Approximately 40% of all accidents occur at intersections – 50% of these accidents involve serious injuries and 20%, a deadly victim.
About 61% of accidents at intersections imply a turn on the left. Left turns are usually the least frequent movement in a cross, so 61% is a considerable number.
Why are the left turns inefficient for the flow of traffic?
Concern: When vehicles that make a left turn are waiting for the opening, they can block the movement of other lanes, especially when several vehicles wait to turn left.
Instead of the fixed green light, many intersections use the green arrow to allow the circulation of vehicles that make a turn on the left. But for that, all other movements at the intersection have to stop. Stop the rest of traffic just to meet some left turns Makes the intersection less efficient.
Also, each time it changes to another “phase” of traffic – such as the green arrow – the intersection has a brief period when all traffic lights are red. Traffic engineers call it Time Totally Redand that’s when the intersection is not serving any vehicle. Totally red time is two to three seconds by phase change, and this time lost accumulates rapidly, making the intersection even less efficient.
What restrictions were tested in different cities?
Concern: When the city center is not very busy – outside the end periods – allowing turns on the left, it is acceptable, because it does not need this additional capacity to move the vehicles in each intersection.
Some cities are implementing Signs that prohibit the turns On the left at the intersections from 7am to 9am, which is the Tip Time in the morning, or from 4am to 6pm, which is the tip of the afternoon. In San Francisco, for example, Van Ness Avenue restricts left conversions during the end hours.
But cities are not implementing these large -scale restrictions. Restrictions are more frequent along individual corridors or isolated crosses instead of virtually the entire city center whenever possible. This would make the center network of the center more efficient.
Rotundes are an approach to avoid left conversions
Concern: The roundabouts are safe because there is no need to cross traffic to the opposite direction. All circulate in the same direction. Find out where you need to go and go.
But restrict the turns on the left, in general, It’s more efficient. The roundabouts are not so efficient when they are busier. The roundabout is full, which can cause congestion, and no vehicle can move. Traditional crosses are less likely to congestion.
The roundabouts also occupy more space. Installing a roundabout can mean widening the cross. In some centers of the city, this means demolishing buildings or remove tours. Restricting left turns requires only one signal that says “left turns on the left” or “forbidden left turns during the most influential hours.” And that.
What are the benefits of banning left turns in urban areas?
Concern: Anyway, eliminating turns to the left will result in longer distances. I will have to travel a greater distance to get where I need it. The worst scenario is having to go around the block. In fact, I’m going through four more blocks to get where I need it.
But not all trips require turning around the block. In a typical city center, each trip will take an average of about one more block. This is not a very large distance. And this extra direction is more than compensated by the fact that each prohibited left turn Move more vehicles. Which means that on average, each time it is in a cross, expects less time. Thus, it travels a slightly greater distance, but it reaches its destination faster.
Avoid left turns improves fuel efficiency?
Concern: Our investigation found that although vehicles travel longer distances on restricted left conversions, they spend less fuel – About 10% to 15% less per trip – Because they don’t stop at intersections.
This is why UPS and other fleets direct their vehicles to avoid turning left. There is less idle and fewer stops.
Do you think forbidding left turns on the left?
Concern: It’s a new strategy, so it’s uncomfortable for some people. But when they get faster, I think people will join.
