RTC study takes aim at inefficienct stoplights

The problem with stoplights, Jim Poston says, is that the costs of their inefficiencies and the benefits of making them work better are so tiny that no one pays attention.

What's the cost of a wasted minute for a salesperson who misses a light on her way back to the office? For a delivery driver making his rounds?

But multiply those minutes by thousands of people spending extra minutes at stoplights around Reno and Sparks all day long, and the costs not to mention the extra pollution from waiting vehicles begins to add up.

Poston, the Regional Transportation Commission engineer who's managing a project to improve the region's system of traffic lights, says the project is almost mind-boggling in its complexity.

Consultants and contractors have been standing at intersections around town since November, counting cars and watching how traffic stacks up in left-turn lanes.

Even though the project covers only 180 of the 340 signalized intersections in Reno and Sparks, it's a bunch of work.

Automated traffic counters those black hoses that cross roadways don't work well on signalization projects because they don't account for turning vehicles.

The data about traffic flow will be crunched by the consultants' computer. But the computerized suggestions for the timing of traffic lights won't be in place until engineers go out and take another look for themselves.

"I think this is at least 50 percent art," says Poston.

How long, for instance, should motorists on a side street wait for a green light so they can cross a busy thoroughfare such as McCarran Boulevard? What happens to traffic on Sierra if the left-turn light on California Street stays green an additional 10 seconds?

Remember, too, that a signal-light sequence that represents good timing on lightly traveled streets at 6 a.m. may create gridlock during rush hour 90 minutes later.

And remember that rush-hour in distant locations comes earlier in the morning as folks begin to leave their homes, and rush hour comes later near businesses as commuters arrive for work.

"Ideally, the timing matches the traffic conditions," Poston says.

But the timing of traffic signals in Washoe County hasn't been reviewed for seven years, and traffic patterns have changed dramatically as the region boomed.

The re-timing project, a partnership of RTC, the two cities, the county government, the Nevada Department of Transportation and the U.S. Federal Highway Administration, is budgeted at $630,000.

But even that much money can't lead to perfectly synchronized lights that allow motorists to zip through town. That, Poston says, represents an impossible dream.

"If you have a one-way street in the middle of nowhere," he says, "it's child's play to time a signal."

Things get complicated, however, when intersections include left-turn signals. And the computers in Reno and Sparks that run traffic signals don't time just one light, but are programmed to recognize the amount of traffic that's coming through other nearby intersections. And the lights at each of those intersections, in turn, are timed to reflect conditions even farther downstream.

It's all a far cry from the days when a timer at each traffic light in town a timer something like the one that turns on your living room lights when you're out of town operated on a never-changing schedule no matter what the traffic conditions.

The goal of the traffic engineers working on the project is a 10 percent reduction in delays and traffic stops once the lights are re-timed this spring and summer.

"Everyone has a value on time, and what we're doing is saving time across the region," says Poston.


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