Traffic changes yield savings in Cranberry

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A highly technical, intensively detailed study of Cranberry's traffic signal system in its commercial center has yielded a take-away message that's as elementary in its simplicity as it dramatic: "Spending money on maintaining the traffic signal system is recouped many times over," summed Cranberry Assistant Manager Duane McKee.

The findings of a year-plus study by researchers at Carnegie Mellon University were presented to township staff and elected officials recently, confirming what Mr. McKee and others sensed from the get-go.

Traffic synchronization -- coordinating signals such that traffic flows through the road system at the best pace possible -- saves time and money.

In partnership with the Southwest Pennsylvania Commission, the township spent $160,000 in 2011 to retime 44 traffic signals along Routes 19 and 228 from Adams Ridge to the east, Powell Road to the west, North Boundary Road to the north and Thorn Hill Road in Marshall to the south.

Traffic data and nationally accepted models for transportation flow were combined to yield what officials deemed to be the ideal timing scenario.

Then came the research team from CMU.

Looking at environmental impacts, fuel costs, lost time, and other components associated with traffic flow, the researchers determined that the tweaks to the system saved the township some $2 million in direct and indirect costs.

"There's a lot of fancy models they run the data through but, in the end, they've determined that the community and the driver is saving money when the traffic signal timing is working the way it should," Mr. McKee said.

There were other benefits that weren't as easily quantifiable: less aggravation and aggressive driving, among them.

The CMU study solidified a decision by the township to enhance national recommendations that traffic signals be retimed and resynchronized every five years.

"We were doing it every three to five years," Mr. McKee said. "Now, we see we need to do every one to two years.

"This study proves without question that in high growth areas or in areas with complex traffic patterns, management of the signal systems must be more proactive."

The findings of the study, which lasted a year, are to be presented at a national conference of civil engineers in Texas in November.

Mr. McKee said the job of retiming is getting easier as the township has acquired more sophisticated computer software for both counting and detective vehicles and traffic movement.

Cranberry's last retiming of the critical routes 19/228 corridors was in late 2011 and a new round of retiming, with the help of SPC, is being initiated now. "Our goal is to do this every two years," he said.

In addition to using computers data collection systems, the township actually sends people to count vehicular turning movements at each intersection as well traffic that moves straight through those same intersections.

The information is collected for morning, evening, midday and weekends.

The new retiming changes will be implemented around November.

In March 2011, Cranberry entered into the agreement with CMU to assist the university with its "Traffic21" project -- a university-wide research initiative aimed at integrating technology with public transportation projects. CMU picked Cranberry for the study because of its advanced traffic data collection system.

Cranberry has a traffic operations center at the public works building off of Route 19 that uses sensors and cameras to evaluate traffic volumes and incidents that snarl traffic.

The program uses wireless technology to coordinate the signals.

In real time, Mr. McKee said the light retiming saved commuters about two minutes at signals.

Transportation - neigh_north

Karen Kane: kkane@post-gazette.com or 724-772-9180.


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