San Marcos Mercury | Local News from San Marcos and Hays County, Texas
Email Email | Print Print --

December 17th, 2012
City activates traffic pre-emption system for fire, EMS

City of San Marcos traffic engineers Sabas Avila, Ning Zou and Cristoval Gonzales check the new traffic pre-emption system that allows fire trucks and ambulances on emergency calls to control traffic signals at intersections. In the fire truck is Fire Capt. Frank Arredondo. PHOTO by DON ANDERS


The San Marcos fire and transportation departments went live last with a new system that allows fire trucks and ambulance to control traffic lights at intersections while en route to emergencies and other calls for service.

In March, the fire department was awarded a Federal Assistance to Firefighters grant which covered 90 percent ($345,420) of the system’s total cost of $383,800.

The City used budgeted funds to pay the 10 percent match of $38,380.  The project was supported by U.S. Senators John Cornyn and Kay Bailey Hutchison and U.S. Rep. Lloyd Doggett.

The city’s Transportation Department equipped 50 signalized intersections with a new Opticom traffic signal pre-emption system. The Opticom system allows fire trucks and ambulances responding with emergency lights and sirens to get the green light at the intersections. It is expected to reduce response times for emergency services.

“All Fire Department vehicles and San Marcos-Hays County EMS units operating in the city have been equipped to activate the system as needed,” Fire Chief Les Stephens said. “Future intersections within the City will also be equipped with this technology.”

The emergency vehicles are equipped with a device that transmits a signal to a receiver located at each of the City’s traffic signals requesting preemption of the signals normal operation. The receiver relays that message to the signal control box to give the approaching emergency vehicle a green light.

“This also allows motorists traveling in the same direction as the responding emergency vehicle to travel safely through the intersection where they can pull to the right and allow the emergency vehicle to pass,” Stephens said.

At the same time, the system prevents potential intersection accidents by turning opposing and cross traffic lights red. The system includes global positioning equipment that uses Department of Defense (DOD) satellites to track the emergency vehicles, and a smart system to calculate the time of arrival of those vehicles at equipped intersections.

If two or more emergency vehicles approach an equipped intersection from different directions, the first arriving vehicle will capture the intersection, and the other emergency vehicles will need to approach with “due caution”—the technique used before the pre-emption system was installed.

“Whether pre-empting or not, emergency responders will use ‘due caution’ when approaching intersections,” said Stephens.  Drivers should also know that after a traffic signal has been pre-empted, it may take the traffic signal 3-4 cycles to get back into synchronization.

San Marcos/Hays County EMS will also activate the system to reduce transport times when transporting critically ill or injured patients to the hospital.

Intersection accidents are by far the most dangerous for citizens and emergency responders alike and this system virtually eliminates the potential for intersection accidents. Any time fire department vehicles are responding with lights and sirens, chances of accidents, particularly at intersections, are greatly increased.

“While the San Marcos Fire Department has an extremely low accident rate, we believe this system will greatly improve the safety of all vehicles approaching intersections when we are responding to emergencies,” Stephens said.

These systems, which have been in use elsewhere in the United States since the late 1960’s, dramatically improve safety at intersections while minimizing traffic disruptions and reducing response times by 12% to 25%. “We anticipate improvements in our response and transport times which will allow us to reach emergency scenes and deliver patients to the hospital quicker and safer,” he said.

In addition to the Opticom system, the Transportation Department also installed broadband radios at each intersection and video servers at key intersections to bring back video and traffic information from the field.  These improvements will allow traffic and emergency management personnel to monitor and assess traffic situations in real-time.

Email Email | Print Print


Leave a Reply

Your email address will not be published.