CDOT tweaks timing of traffic lights | AspenTimes.com

CDOT tweaks timing of traffic lights

Carolyn SackariasonAspen, CO Colorado

ASPEN Motorists now have to wait longer to turn onto Highway 82 from side streets, but those extra seconds translate into hundreds more cars getting into town quicker.That’s the rationale of transportation officials, who for the first time have changed the timing of traffic signals at the Entrance to Aspen to accommodate the high volumes of summer traffic. City transportation officials count about 29,000 cars coming in and out of town on a daily basis during the summer.”The whole concept is to tweak it to get more efficiencies out of the lights,” said Jim Nall, a traffic and safety engineer for the Colorado Department of Transportation.The changes allow more “green time” for motorists on Highway 82, delaying those who turn left off of Harmony Road, the Airport Business Center, Owl Creek, Truscott Place and Cemetery Lane.Since June 20, left-turn signals have been shortened to allow three to four cars per cycle. The Truscott signal has been changed to allow left turns 180 seconds after a vehicle is detected. The other signals are set to allow left turns after 90 seconds. The goal is to have vehicles on Highway 82 travel continuously until there is a demand from the side streets.”Traffic is like water – you are trying to get four inches of water through a four-inch pipe,” Nall said. “Seconds over an hour can add up to 100 cars going through a traffic light.”The new timing sequence is a pilot program and will change again to accommodate ski-season traffic patterns, transportation officials said. Between 23,000 and 24,000 cars come in and out of town each day during the winter. Traffic volumes are much different during the winter because many people take the bus to ski areas, and kids are in school, said John Krueger, the city’s transportation program manager.”In the summer, traffic is all day instead of at peak times,” he said. “It goes up and stays up all day.”Currently, the signal cycles are timed to improve traffic flows in the mornings and afternoons, as well as off-peak times. However, the traffic signals are not synchronized because during significant portions of the day and night there is light or inconsistent demand for turning off the side streets. “When you get into coordinated lights it gets difficult,” Nall said. “It takes a whole team of engineers to figure it out.”Some lights have cameras, and others have a magnetic strip that tells the signal controller that a car is there. If a vehicle is there during the beginning of the cycle, it will go first. Arriving at the signal at the end of its cycle, a vehicle could wait up to three minutes before the light changes.”It seems like a simple thing, but it’s complicated,” Krueger said. “It’s as much a science as it is an art.”It’s too soon to tell if the changes have helped, he added.”It was never seen as a solution. … We just have too many cars, too much capacity,” Krueger said. “I think they are still looking at it but it does seem to be helping, especially at Truscott.”City officials asked CDOT to eliminate all left-hand turn lanes from Cemetery Lane and Truscott Place onto Highway 82 from 3-6 p.m. for the summer, but that has yet to happen.”We’ve been resistant to do that until we can study the impacts, both positive and negative,” Nall said, adding that safety is an issue because motorists who must take a right on Highway 82 might elect to make an illegal turn farther down the road to head in the direction they needed to go in the first place. “We would want to know that people who are taking a left turn have an alternative.”Krueger said traffic volumes have increased about 5 percent over last year’s average, which is calculated on an annual basis and is between 23,000 and 24,000 a day. Even though traffic might seem unbearable, today’s levels are close to what the 1993 Aspen Area Community Plan says is acceptable.There are up to 1,200 an hour cars going through the Cemetery Lane traffic light. A comfortable level is between 700 and 800 an hour, Krueger said.”We’ve made small modifications but there’s a limit,” he said. “Once you’re at capacity on the roadway system, you just can’t add any more cars.”


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