Janesville79.5°

Believe it or not, traffic signals are made to aid traffic flow

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GINA R. HEINE
October 22, 2008
— You're sitting at a red light.

The line of cars inches ahead anticipating the green light. When the light changes, the drivers race five blocks only to slam on the brakes as the next light turns red.


Why aren't all stop lights synchronized to keep traffic moving?


Drivers often raise that question and many other traffic signal-related complaints to city engineers.


"People don't like to wait, and we understand that," said Jack Messer, city public works director, "but that's the nature of a traffic signal—(they have) to make somebody wait."


With high gas prices, drivers constantly are looking to increase their mileage. Janesville has five streets or pairs of streets where the signals are timed to maximize movement, Messer said.


But more could be done nationally, the National Transportation Operations Coalition said in its report last year.


It estimates improper traffic signal timing on major national roadways accounts for 5 to 10 percent of all traffic delay, or 295 million vehicle-hours of delay. If the nation supported its signals at peak efficiency, the coalition said drivers could cut fuel consumption by up to 10 percent.


"A driver who uses one tank of gas a week would save five full tanks per year per household, or approximately $240.14. Nationwide, this would amount to a savings of almost 17 billion gallons of motor fuel per year," the coalition's 2007 report said.


How it works

Timing of traffic signals is a science, an engineer will tell you.


"It's a programming function of a computer, essentially controlling traffic with a computer with signal system," Messer said.


The city has synchronized lights on five streets or pairs of streets based on "the most frequent occurrence of traffic," he said, though there will be times when the signal set up doesn't optimally match the traffic conditions.


The coordinated systems are:


-- Milton Avenue from Mt. Zion Avenue to Kettering Street. The major thoroughfare sees about 25,000 vehicles a day, and the signals favor southbound morning commuters. By afternoon, traffic is more even so the signals favor both directions.


-- Highway 14/Humes Road from Bell Street to Pontiac Drive.


Milton Avenue and Highway 14 are individual coordinated systems, but the major intersection of Highway 14/26 also is coordinated.


-- Center Avenue from State to Racine streets.


-- Centerway from Jackson Street to Parker Drive. The Five Points intersection is not included.


-- Court and Milwaukee streets in downtown, which are on a pre-timed system, not on traffic sensing.


"The goal is to be most efficient. That doesn't necessarily mean get through the entire system on green because you're dealing with all of the traffic," Messer said. "You have to take time from one group of people to give to another group of people."


The systems are altered for special events or times of year, such as the holiday shopping season, he said. For example, signals around Farm & Fleet are adjusted during the early morning hours when Toyland opens.


While it might seem like an eternity, most of Janesville's signal cycles are less than two minutes, Messer said. That includes the green, yellow and red lights for all directions.


Sensors

Many of the actuated signals—those not on a coordinated system—rely on wires in the pavement that create a magnetic field.


When a car breaks the magnetic field, it trips the computer to give priority to that direction, Messer said.


At most of those signals, traffic in one direction is favored with the green light until a vehicle approaches and is sensed on the side street, he said.


One vehicle should be enough to trigger the sensor, but the sensors frequently malfunction, he said.


Emergency preemption

The majority of Janesville's 75 traffic signals recently received emergency preemption sensors. When a fire engine or ambulance responding to an emergency approaches a signalized intersection, the sensors preempt the signal to give green lights to the emergency vehicle.


The interruption causes delay afterward, though, Messer said.


"If you're sitting at one that's been preempted, you will notice some significant delays as (the signals) cycle back through," he said.


Messer understands the frustration of some inpatient drivers.


"In reality, things work pretty well in Janesville," he said. "(You) don't see heavy delays, don't see huge backups."


REPORT A PROBLEM

Traffic sensors or the signals themselves often malfunction, public works director Jack Messer said.


"If you're sitting there waiting (for what) seems unreasonable, it could be malfunctioning," he said. "We're not going to know that unless someone calls."


If that's the case, report it to the city at (608) 755-3110.


CITY MIGHT REMOVE SEVEN TRAFFIC LIGHTS

Janesville's 2009 budget calls for removing seven traffic signals, public works director Jack Messer said.


His department was tasked with removing $14,000 from the budget by removing seven signals. Each intersection with signals costs about $2,000 annually in maintenance and electricity, Messer said.


The city council could decide not to approve removing the signals, but for now Messer and his crew identified 12 signals to be studied:


-- Main Street and Centerway


-- Delavan Drive and Ogden Street


-- Wright Road and Brunswick Lane


-- Milwaukee and Academy streets


-- Beloit Avenue and State Street


-- Jackson and Elliott streets


-- Racine and Jackson streets


-- Beloit Avenue and Conde Street


-- Jackson Street and a driveway into General Motors


-- Wright Road and Park View Drive


-- Milwaukee Street and Harmony Drive


-- Jackson and State streets



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