A GPS tracking system that also can help thwart bus thefts and deter terrorist hijackings is gaining in popularity in the motorcoach industry.

More than 100 over-the-road and tour-and-charter bus companies, with fleets ranging from a single bus to several hundred, have installed Saucon TDS devices on their coaches.

And sales this year could double as many more operators move to not only have sophisticated tracking systems onboard their coaches but try to prevent them from being stolen by miscreants or hijacked by terrorists and turned into deadly weapons.

Manufactured by Saucon Technologies of Bethlehem, Pa., the GPS devices allow operators to remotely slowdown and stop a bus and shut down the engine so it cannot be restarted.

The company has sold about 1,000 of them a year since they were introduced to the motorcoach industry about three years ago. Sales this year, however, are on track to top 2,000, which would result in more than 5,000 being on the road in the United States, according to Saucon managing director Bill Bouffar.

The growing customer list includes biggies such as Coach USA, which has the units on about 1,500 of its buses on the East Coast and its Gray Line affiliate, which uses them on some of its double-decker tourist buses.

"We were interested in getting GPS systems on our coaches and these ones have all of the bells and whistles so we decided to go with their devices," said Gary Pard, vice president of DeCamp Bus Lines, a commuter service in Montclair, N.J., that plans to equip all 80 of its coaches with the system.

DeCamp was just approved for a $136,000 grant from the U.S. Department of Homeland Security that will be used to buy and install the units.

Most of the companies buying the devices have used federal security grants to purchase them, according to Bouffar. They cost about $1,500 each and require a monthly service fee of about $50, depending on the type of service purchased.

Bouffar said the devices provide a wide variety of routine tracking services from pinpointing the location of a coach to monitoring engines, transmissions and tires. They also can alert the company dispatcher if a coach is traveling faster than a preset speed.

But the feature that coach operators are talking about the most is its theft and terrorist deterrent capability.

The driver activates the system by pressing a panic button, sending alerts to the bus companys dispatcher and Saucons help desk. From either command center, the bus can be remotely slowed down and gradually brought to a stop. Once it is stopped, the engine can be shut down so it cannot be restarted.

Such action could prevent a terrorist from driving the coach to a target, such as a bridge, tunnel or government facility, and give police time to reach the location of the coach.

"We figure if the driver stopped suddenly, the terrorist might blow up the coach, but if it slows down gradually, it could give them time to re-think what theyre doing," suggested Pard, who hopes to have the units on the DeCamp buses in two or three months.

Bouffar said the emergency system so far has been activated twice after buses were stolen. In one case, police went to the scene and made an arrest. In the other, the thief parked the bus and the system was used to kill the engine to prevent the bus from being driven further.