When Rola Idriss's cellular phones home, it's delivering data from Interstate 10 to her office in Engineering Complex I.

The phone is attached to the nation's first large-scale bridge that can report its structural health to a remote location. The bridge, which leads motorists from University Avenue onto Interstate 10 westbound, is part of an NMSU experiment that could revolutionize the way bridges across the country are inspected.

"This bridge in Las Cruces is becoming famous," said Idriss, a civil engineering associate professor. "Being able to monitor bridges from far away has great implications."

If the experiment proves successful, the system may be implemented in bridges nationwide, said Idriss, who rigged the bridge with sensors that report its well-being. Such systems - "smart bridges" - will provide faster, less-expensive and more thorough bridge inspections, she said.

About 40 percent of nation's 578,000 bridges are "structurally deficient or functionally obsolete," according to statistics from the Federal Highway Administration. Idriss simply says many are "in bad shape."

"The question is how to maintain aging bridges so that we don't have to build new ones," Idriss said. "We can repair them if we know where and how they're damaged."

An experiment similar to Idriss's but on a smaller scale was conducted in 1993 by engineer David Prine of Northwestern University. Prine installed a remote monitoring system of eight strain gauges on a Wisconsin bridge over Sturgeon Bay.

The Las Cruces interstate bridge is rigged with 30 sensors. It is a typical highway bridge from the '70s built with eight 100-foot steel spans including an on-ramp. One span of the bridge is wired underneath with instrumentation including a computer, sensors and a cellular phone, all too small for motorists to notice. The phone is used to transmit data to NMSU.

"The sensors report the stress in the bridge and give information on the level of the load and how many trucks are going by," Idriss said. "From the data we will know the stress level at which it's working and how far we are into the fatigue life of the bridge."

Before the data can be analyzed, Idriss must develop a system to evaluate the information. "You have baseline data for the structure, which gives a pattern of behavior," she said. "A change in it could indicate damage or deterioration and should be evaluated."

The monitoring system will be a valuable tool for bridge engineers, allowing them to make better decisions when evaluating older bridges. Engineers may decide to strengthen a bridge rather than replace it, which could save millions of dollars, Idriss said.

"Maybe you need to reinforce the bridge a bit and it will be fine - or maybe it is unsafe," she said. "The monitoring system gives the engineer the data so she can make the assessment."

Before she took her research to the field, Idriss conducted tests on a 40-foot-long bridge built for experimentation in a laboratory. She wired it with 48 optical sensors that detect movement, stresses and damage - and called it a smart bridge. Before that, she conducted stress tests on an Interstate 40 bridge near Albuquerque that was slated for demolition. Engineers cut a six-foot fracture into the bridge, drove an 82,000-pound truck over the break and monitored its reaction.

"We held our breath, and someone said, `What's holding it up?'" Idriss said. "But I knew from computer analysis that it wouldn't fail."

Catherine Lazorko, '95