Updated

When more than 22,500 runners hit the streets for the 110th Boston Marathon on Monday, they'll be teaching public health and safety officials how to better respond to mass casualty events like Hurricane Katrina.

All runners will have a bar code on their bibs so organizers can track them using handheld scanners should they require transportation or hospitalization during the race.

The immediate goal of the runner tracking system is to make sure organizers don't lose any participants during the 26.2-mile event. But public health officials say it could also test a mechanism for tracking victims of natural disasters or terror attacks through medical tents and shelters.

Unlike the electronic chips that many road races use to follow runners along the course and record their times, the bar codes are meant to track people off the route and make sure they don't get lost in the health care system.

"It's not uncommon at the end of the day to have hundreds of family members knocking on the tents trying to figure out where their runners are," said Chris Troyanos, the medical coordinator for the Boston Athletic Association, the marathon's organizer. "It's one of the biggest problems for us."

Nancy Ridley, associate commissioner for the state Department of Public Health, said the marathon provides a good training ground to test a patient tracking system, something federal and state officials have been talking about more and more since the Sept. 11 terrorist attacks and Hurricane Katrina.

During Katrina, she said, "you might have thousands of people being treated all over the place but there was nothing that fed that back to a central repository to try to connect people together or connect them into support systems. People were getting lost after being plucked from roofs. Something like this could help."

Should a runner get sick or drop out of the race, a staffer with a wireless device will scan the bar code from the bib as that runner walks into a medical tent.

After the runner's identifying information — name, gender and age — appears on the handheld's screen, the tent staff will note that person's basic medical need. No specific medical information will be stored in the system.

Runners who are treated and released at the tent will be scanned on the way out to note that they've left. If someone's transferred to a hospital, that also will be documented on the device, which feeds the information into a larger system.

Unregistered runners or spectators who need help will be given a wristband with a bar code.

Family and friends will be able to go to an information kiosk near the finish line and ask if their runner has sought medical help.

"Everyone running the race knows they have family at the end waiting, hoping everything's OK," said runner Mark Spencer, 49, of Andover. "This is nice in that you know no matter what happens, someone will know where you are and how you are, and could find you if needed."

Safety officials can also analyze trends. If they see many people dropping out at a certain point, they can check for any hazardous conditions there, said Peter Judge, spokesman for the Massachusetts Emergency Management Agency.

Medical staff can also sort the data by injury or tent to make sure certain supplies don't run out.

The technology is being financed through a grant from the federal Health and Human Services Department. Ridley said each state has been told to come up with plans for patient tracking or other measures that would help emergency response in natural disasters or terrorist attacks.

In a good year, there are about 800 to 900 runners in the Boston Marathon who require medical attention. In a bad year — when outside temperatures spike — as many as 1,700 people have needed aid, Ridley said.

"I've dropped out in the past and had to wait a long time to hook up with family and friends," said David McNicol, 45, of St. Andrews, Scotland, who will run in his 11th Boston Marathon. "This sounds very positive and useful to have a record of you along the way."