Driving You Crazy: The turn arrow on eastbound Iliff at Abilene isn't long enough!

Why isn't it a longer arrow?
Posted at 8:19 AM, Nov 28, 2017
and last updated 2017-11-28 10:19:11-05

Ashlye from Aurora writes, “What is driving you crazy? The left turn arrow, to turn from eastbound Iliff onto northbound Abilene, only stays green long enough for two cars to turn, and then it turns yellow and immediately red. During rush hour and heavier traffic times, you can sit through the arrow 3-4 times before turning! Why isn't it a longer arrow?”

That is not the only intersection around town that has that same problem Ashlye. If I come up to one of those lights that I know is bad I more often than not will turn right and then flip around and avoid the left turn all together. That move isn’t possible at that turn or I would find myself driving the wrong way on northbound I-225.

I asked Aurora Public Works about that problem. They tell me depending on the time of day and day of the week, the signal could be operating “free” or in one of four different coordination plans.

“Available green time during coordination varies from a minimum of 6 seconds to a maximum of up to 12 seconds depending on the plan active and the numbers of vehicles present on the movement,” said Julie Patterson with the city of Aurora.

Let’s give the first driver the benefit of the doubt and they aren’t checking their Facebook page while waiting to turn. I would think it would take that driver on average two of those seconds to react after the light turns green and hit the gas. That would leave four seconds to get maybe two or three other cars to make the turn before the light changes to yellow. I would estimate that another three or four or maybe five more cars could make the turn if the timing was up to 12 seconds and they were all paying attention.

Aurora Public Works says they base their timing plans on several considerations including the number of lanes at the intersection, the configuration of intersection and the typical volume of traffic making each movement during the time allowed by each signal cycle.

“Within each cycle length, the amount of green time available to a particular movement is typically allocated proportionately with regard to the volume present on that movement as compared to the total volume present at the intersection,” said Patterson. “The through movements on the major road at an intersection are typically the highest volume and therefore typically receive the greatest amount of time—this is also important for progressing through traffic along an arterial route.”

The City of Aurora’s next citywide traffic signal timing study is currently scheduled for next year. It could even spill into 2019 depending on how long it takes. The good news is that the entire Iliff corridor is in the first phase of the study. Aurora Public Works anticipates they will be making updates and changes to that signal, as well as other intersections, after the study is finished.

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