With gas prices soaring, drivers are scoping out every opportunity to save at the pump. One possible solution: avoid making left-hand turns.
The fairly simple idea — and well-known delivery strategy of UPS — addresses the fact that idling while waiting to turn against oncoming traffic wastes time, and by extension, fuel and gas money.
But does the theory hold water?
According to Dr. Joe Hummer, a professor of civil, construction and environmental engineering at NC State, minimising left turns is fuel-efficient in a couple of ways.
In 2011, Hummer was part of study to determine whether superstreet intersections in North Carolina result in faster travel times. At a superstreet, all left-hand turns from side streets are re-routed so that drivers must turn right and then make a U-turn.
Researchers found that compared to conventional traffic designs, superstreets reduced travel time by 20 per cent overall. According to Hummer, travel time is proportional to fuel use.
At some intersections the delay for left-turning vehicles is so long that those drivers will save time and gas by finding some other way, such as making three right turns, Hummer explains.
Protected green arrows also take time away from through traffic. Many cars are waiting and burning gas while only a few cars are moving.
“If fewer people made left turns, the signal controller could take time away from the green arrow and give more time to the green ball for through vehicles and right turn vehicles,” said Hummer. “Since there are typically many more through vehicles than left-turning vehicles, the net effect would be fuel savings.”
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