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Why doesn’t the left-turn lane from College to Waltmoor have a flashing yellow signal?

Adam Wagner
StarNews

Q. Why is there no flashing yellow left-turn signal when turning from southbound College Road onto Waltmoor Road, yet at the next intersection of Pinecliff and College there is?

A. The main reason for the lack of a yellow turn signal is many more southbound cars making left turns onto Waltmoor than Pinecliff, said Don Bennett, the City of Wilmington’s traffic engineer.

That means Department of Transportation standards call for a protected green arrow instead of the flashing yellow arrow.

DOT multiplies the left-turning volume by the volume of through traffic opposing the term to come up with a number, called “cross product,” that then determines how the intersection will be handled.

So at Waltmoor and College, for instance, the cross product would be determined by multiplying the number of cars turning left onto Waltmoor from the southbound lanes of College Road by the volume of northbound cars on College Road.

Another factor engineers have to consider is sight lines, both in other locations and in the cases of Waltmoor and Pinecliff.

At roads such as Waltmoor, where many drivers are making left-hand turns in both the northbound and southbound lanes, it can be difficult for drivers to see well enough to turn safely.

“Where dual left turning movements are present, there is sufficient traffic to assume that both lanes are frequently used and sight lines (for turners) are obstructed,” Bennett wrote.

Pinecliff, meanwhile, has about as much northbound through traffic but many fewer southbound left-turners than Waltmoor.

At roads such as Pinecliff, where there are fewer total left-hand turns, drivers have a lower chance of blocking each other’s sight lines by making opposing left turns. Thus, the flashing arrow is a viable option.

“In the event that two left-turning vehicles are present at Pinecliff and the drivers are unable to see, they are able to wait until an arrow comes up and provides them with a protected, unopposed movement,” Bennett wrote.

RELATED LINKS:

Why do people think they have the right-of-way turning left onto Oleander?

Why do some left-turn arrows at intersections only work sporadically?

User-contributed question by:
Edward Orde

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