Wednesday, April 9, 2014

The case for almost never turning left while driving

From: Washington Post

“All truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident.” — Arthur Schopenhauer

Please remember that quote as I propose what will appear outlandish — a ban on left turns on heavily-trafficked roads. Making left-hand turns is as American as apple pie. But remember, we once accepted slavery and the beating of wives and children. There’s no doubt we’re doing things today that future generations will find abhorrent. Here’s why turning left on crowded streets is one of them:

Left turns are unsafe for everyone.

Federal data have shown that 53.1 percent of crossing-path crashes involve left turns, but only 5.7 percent involve right turns. That’s almost 10 times as many crashes involving left turns as right. A study by New York City’s transportation planners concluded that left-hand turns were three times as likely to cause a deadly crash involving a pedestrian as right-hand turns. And 36 percent of fatal accidents involving a motorcycle involve a left-hand turn in front of a motorcycle, according to the National Highway Traffic Safety Association.

“Left turns create some concerns when it comes to generating potential for congestion, back-up traffic flow, safety, accident situations,” said Phil Caruso, the deputy executive director for technical programs at the Institute of Transportation Engineers. “So if you can eliminate left turns, especially concurrent left turns, that’s a positive.”

We could save lives by restricting left turns, but we’re unwilling to sacrifice what we see as a needed convenience. Even if you discount the safety concerns, the efficiency of turning left is questionable.

Engineers don’t like left-hand turns.

Tom Vanderbilt, author of the popular book Traffic, has called left turns “the bane of traffic engineers.” Solutions such as diverging diamond interchanges have been proposed. Here’s the problem with left turns, according to Vanderbilt:

It’s either a car stopped in an active traffic lane, waiting to turn; or, even worse, it’s cars in a dedicated left-turn lane that, when traffic is heavy enough, requires its own “dedicated signal phase,” lengthening the delay for through traffic as well as cross traffic. And when traffic volumes really increase, as in the junction of two suburban arterials, multiple left-turn lanes are required, costing even more in space and money.

UPS: A case study in why left turns are rarely needed.

Ask any driver if they think they’d get to their destination faster and burn less gas if making almost no left-hand turns. Their answer will almost certainly be no.

Then consider the opinion of one of largest shipping and logistics companies in the world, which stakes millions on efficiency. UPS has chosen to minimize and sometimes eliminate left-hand turns to be more efficient. The company says the changes have helped it save millions of gallons of fuel. Whose opinion should we trust?

“Number one, you have a safety factor of crossing traffic, and number two, you have the delay factor, particularly in busy roads. I’m talking commercial; I’m not talking residential roads,” UPS senior vice president Bob Stoffel explained to Fortune.

It’s important to note that UPS policy is not a 100 percent ban on left-hand turns. One UPS official estimated that the company’s trucks turn right 90 percent of the time. If in a residential area where traffic is light, a left-hand turn is sensible. Or if a series of right-hand turns would take a driver far out of his way, a left-hand turn is efficient.

“We’ll never have a person turn left to deliver on that side,” Stoffel said. “We’ll have someone go down the right-hand side and someone coming back down the right-hand side to avoid those left-hand turns. And that’s where you get stuck in traffic trying to come back across.”

Given our country’s tradition of making left-hand turns and our fondness for personal freedoms, it’s unlikely that left-hand turns will be limited on more than the occasional basis. There may not be hope for human drivers, but perhaps the coming self-driving cars will do the right thing.

No comments: