Future of traffic signals is named RHODES August 29, 2000 I've seen the future of traffic signals, and it's in Tempe. At the corner of Rural Road and U.S. 60 - the Superstition Freeway - a computer-run system is changing the way traffic signals work. It differs from the conventional way: preprogramming cycles for a certain amount of red and green time for each traffic movement. Instead, RHODES (Real Time Hierarchical Optimized Distributed Effective System) looks down the road for waves of approaching traffic, estimates when that traffic will arrive at the signal, and - if it's working properly - the light will be green when the traffic gets there. In short, the old cycles are replaced with a real-time system that adjusts on the fly. So far, it's just a test. Tempe's been running the RHODES system about two weeks, and it'll be in place at least a month longer. To keep the test honest, some days RHODES will be switched on, others not. In Tucson, a similar test will run in January on a heavily traveled portion of Speedway Boulevard, near the University of Arizona. "Hopefully, people will experience fewer stops," said David Lucas, a research associate for the RHODES project at UA. In Tempe, Jim Decker, who runs the city's traffic signals, is cautiously optimistic about RHODES. "We need more work to get it right, but we're making progress," Decker said. Cameras are posted high atop light poles to watch for traffic. The cameras read the traffic, and send a message to the Tempe traffic control computer. From there, it travels over a dial-up modem to an on-site computer at the intersection. The computer sends a message to the signals, which then turn green in time for the arriving flotilla. "It's a pretty complex operation for a very simple thing: red, yellow and green," Decker said. Drivers, of course, want more green, and if successful, RHODES could be expanded to handle Rural Road, among Tempe's busiest north-south streets. It could also be helpful in moving big-event traffic near ASU. Does it work? Sometimes. "I've driven up and down (Rural). A lot of times I make it through (U.S. 60) and sometimes I don't," Decker said. "I have to figure out why that happens." It seemed to be operating fine midafternoon Monday at Rural and the freeway, which handles about 60,000 cars a day. The computer told the light on Rural Road to change to green, and seconds later, a wave of cars approached and made it through effortlessly. "We get an idea of the (traffic) demand once they get here," Decker said. An independent firm will collect the Tempe and Tucson data and determine whether RHODES is worth continuing and even expanding. Federal funds are paying for the tests and equipment. Tucson officials, interviewed earlier this summer at a state transportation symposium, told me they like what they've seen of RHODES. The software itself would add an additional $1,000 per intersection, but the other sensors, radar equipment and cameras, could really make things pricey. The payoff, though, could be smoother flowing traffic and shaving seconds off drive times. "It needs more work, and it's very early," Decker said of RHODES. "But if you don't push the envelope, you won't find out. The status quo is unacceptable." Reach Petrie at bumper@arizonarepublic.com or (602) 444-7941.