DENVER -- Smart phones and in-car GPS units may soon notify people of an approaching emergency vehicle before a siren is ever heard.

It's technology a Denver company is developing and preparing to test with West Metro's Fire Department.

It's called 911 ETA and involves software that can be downloaded to a smart phone or in-car GPS unit. The technology indicates on a map where an emergency vehicle is located, notifying the driver to pull over or avoid an area.

The device audibly notifies a person stating, "Caution, an emergency vehicle is approaching" or "warning, approaching road block."

The software on a smart phone vibrates the handheld device for about 30 seconds. The developers said they do not expect people to look at the phone, but just listen and be aware an emergency vehicle is nearby.

The software for in-car GPS units has additional features.

"That version will also have the ability to lower the volume on the radio, lower the air conditioner and perhaps even unroll the windows," said Carl Johnson, the engineer of 911 ETA.

The program is set right now to alert a person when an emergency vehicle comes within 900 feet, but Johnson said each jurisdiction can determine when it wants to notify people.

West Metro Fire agreed to test the software starting in November. Fire Chief Doug McBee said this device could save lives and improve safety on the roads.

"People don't naturally pull over to the right," said McBee. "People panic when a fire truck is right up on top of them and people don't hear it."

McBee said with cars so well sound-proofed and people listening to music while they drive hearing a siren is not always easy.

Johnson said there are 15,000 accidents a year involving fire trucks which injure 1,100 fire fighters. There are accidents where drivers don't hear emergency vehicles and pull-out in front of them or cause other crashes.

The developers said this device will help more than just the deaf and people with hearing loss.

"We become part of that segment of society when we get in our cars, roll our windows up, turn on the air conditioner or the heater and actually turn on the radio or CD player," said Juan Gutierrez, a former Denver fire fighter and developer of 911 ETA. "We are totally insulated from the outside world."

McBee said this system will also allow emergency crews to know where other emergency vehicles are located which are responding to the same incident. He mentioned a crash on Tuesday in Philadelphia that involved a police car and a fire truck.