|
Traffic, speed go into turn decisions
Published October 20, 2009
HOW IT WORKS
Glad You Asked features questions from Facts readers. Facts staff members pose those questions to newsmakers who provide the answers.
POSE A QUESTION
Have a question for Glad You Asked? E-mail news @thefacts.com; fax it to 979-265-9052; or mail it or bring it to our offices at 720 S. Main St. in Clute.
QUESTION: I am curious as to why some intersections in Angleton have traffic lights in which drivers have a choice of an unprotected left turn while most other intersections do not.
For instance, at the intersection of Highway 35 (Mulberry Street) and Walker Street, the light allows for an unprotected left turn onto Walker Street if there is no oncoming traffic.
However, further up the road on Highway 35, there is no such option at the intersections of Anderson, Downing, Cedar or Buchta. Cars must wait, most times excessively long, for the left-hand turn light to turn green.
Why aren’t unprotected left turns an option at every intersection along this route? This seems like a no-brainer to keep traffic at intersections to a minimum.
ANSWER: The topic of operating left turns at traffic signals with either protected phasing (where drivers have a left turn arrow and oncoming traffic must stop) or permissive phasing (where drivers can turn when the oncoming traffic has a green light but must yield) is a topic that generates considerable interest for traffic engineers and the public alike.
Both approaches are acceptable and we consider traffic volumes, speed of traffic and number of lanes on the highway. The protected phasing is safer but not as efficient as the permissive phasing in some cases.
The operation also could depend on when the signal was designed. Several years ago, we installed only the protected phasing, but we are seeing more intersections trending to permissive signals under the right conditions.
Stuart Corder,
Transportation Operations director,
Texas Department of Transportation-Houston District
Share |
Save |
Mail |
Print
|
