Monday, 28 August 2000

Maybe a shorter commute

Chris Richards / Staff
UA's David Lucas, left, and Pitu Mirchandani at Speedway and Mountain, a "smart" light locale.

City will test UA's 'smart' lights system in hopes it'll direct traffic more efficiently

By Anita McDivitt
ARIZONA DAILY STAR

Researchers with the University of Arizona want to test a "smart" traffic-control system - one that can reduce your commute and even predict where cars will go - along a seven-block stretch of Speedway, one of Tucson's busiest streets.

"If it works half as well as the simulations in the lab have been showing, it's almost as if we've put another lane on the street," said city traffic engineer Richard Nassi. "In this day and age, we really can't build our way out of congestion. We need to use the most intelligent transportation techniques we have available."

For nearly a decade, university professor Pitu Mirchandani and a cadre of students have been working to develop RHODES, a system that uses cameras, loop detectors under the roadway and radar to gather information on immediate traffic conditions.

RHODES stands for Real-time Hierarchical Optimized Distributed Effective System.

Where traditional signals work on a predetermined timing schedule, these "smarter" controllers not only know how many cars are waiting at the light - they're also looking farther down the road, communicating with other signals and telling them how many cars to expect in the near future.

It's kind of like having far-sighted traffic officers sitting above every intersection and communicating with each other about traffic conditions.

"It gets the traffic flowing," said Mirchandani. "What we are trying to do is bring down the wait, the delay at the intersection."

Motorists in Tempe were the first to test RHODES, which began operating at the intersection of U.S. Route 60 and Rural Road last week, said Jim Decker, manager of Tempe's Intelligent Transportation Systems.

The intersection handles about 60,000 cars a day, with 350 to 400 hourly turning movements onto the freeway, he said.

"Hopefully, it will offer faster travel times and less congestion at the intersections for motorists," said Decker. "We don't know yet because we haven't evaluated its performance. And we haven't worked all the bugs out yet. But it has huge potential."

Tempe hopes to see a five- to seven-second decrease in the average amount of time motorists spend waiting at the signal. That may not sound like a big improvement, Decker said, but multiply that by 180 intersections in Tempe - or thousands of intersect ions in Phoenix or Tucson - "and you're talking minutes off your drive time."

Tucson's trial run with the system is scheduled for January next year.

Over the past decade, the Federal Highway Administration has invested between $7 million and $8 million in developing this type of technology, said Raj Ghaman, team leader for the agency's travel management research division.

"What we found is that signals should be looked at every six months, but most cities don't re-time their signals for long periods of time, sometimes nine or 10 years," Ghaman said. "If you ever wonder why commuters run red lights, go through residentia l areas, cut through gas stations, it's because they're stuck with the signal timing."

This modern traffic-control system is actually a high-tech version of a system first proposed by one of the "grandfathers" of modern-day traffic engineering, William Eno, during the Roaring '20s.

Eno, who lived in heavily congested New York, suggested that for the traffic signals to be more efficient, the city needed to put a policeman in a "crow's nest" above the street, looking in all directions.

"Basically the logic Eno proposed, of looking ahead, making predictions, getting ready for what's going to happen - that's what Pitu is doing right now," Nassi said. "But we never had the machines or the logic or the software to do it."

Tucson has slowly been getting ready for the test, replacing older traffic signals not capable of running the complex mathematical calculations used by RHODES with new ones on Speedway.

But allowing RHODES to operate may mean changes for some motorists, Tempe's Decker said.

"Most motorists drive by habit," he said. "We have yet to let RHODES do all it can do because we did not want to violate driver expectations."

For example, RHODES has not been allowed to change the order of the lights and turning arrows at the Tempe intersection, although it can - if it decides that is the best way to keep the traffic flowing, Decker said.

"They're going to have to learn to drive by the signal … and not by habit," he said. "But we think it will benefit them, with less delay at intersections and less drive time as a whole."

* Contact Anita McDivitt at
806-7739 or via e-mail at
mcdivitt@azstarnet.com.