Truck driver James Mulhern of Harrisburg, Pa., has designed a new kind of double-decker bus to offer charter service to handicapped travelers and their families.

He has applied for a patent for his invention, a coach 52 feet long, 13 feet 4 inches high and 8 feet wide. Mulhern says that is the same size as an articulated bus or a tractor-trailer rig and larger than the largest standard buses, which are about 40 feet long.

The coach would be pulled by the same kind of tractor that hauls a semitrailer, which Mulhern says has some advantages: If the engine or transmission failed during a trip, a replacement tractor could be dispatched from the company's fleet or rented and sent to the scene quickly. This would enable passengers to continue on their trip with minimal delay and without having to transfer to another vehicle.

Mulhern has designed the coach, which he has named the Amer-I-Can, to hold up to 30 passengers on the lower level and up to 40 on the second level. Wheelchair-bound travelers, who would use the lower level, will be able to stay in their wheelchairs for the trip, because a seat can be removed and the wheelchair bolted into place. They also will be able to transfer into the coach's seats. Either way, every passenger will have a seat belt.

Mulhern said that that it will be easier for wheelchair-bound passengers to enter his Amer-I-Can coaches than standard buses because of a smaller ground clearance: 6 inches compared with about 15 inches.

The coaches will have other features to accommodate disabled passengers, including those in wheelchairs:

*Double-size restrooms.

*Wider aisles, created by having a wider coach body and by placing two standard seats on one side of the aisle and one jumbo seat on the other (for larger passengers).

*More headroom -- 6 feet 4 inches on both levels.

*One foot more legroom than on conventional buses.

Mulhern figures that the coaches will cost about $300,000 each to build. He is hoping that someone will donate a tractor, which costs about $80,000, to pull the first Amer-I-Can coach.

He also said that Goodyear Tire & Rubber Co. will supply tires, and test different kinds to find out which are best for the new vehicle. A Goodyear spokesman confirmed this.

Asked how groups representing the disabled have reacted to his invention, Mulhern replied, "They want it."

One of the people Mulhern talked with was Trudy Ulshafer, executive vice president of the Pennsylvania Association for the Blind in Harrisburg. She called Mulhern's Amer-I-Can coach "an excellent concept for wheelchair-bound individuals." However, Ulshafer also said that she doubts that most blind persons who can travel independently would use a special charter service because they prefer "mainstream," or standard, service. She noted that some blind people also are wheelchair-bound.

A spokesman for Trailways Corp., a major intercity bus operator, also questioned whether the disabled want or need special transportation. He noted that Trailways operates a Helping Hand program under which disabled travelers can bring along an assistant free of charge. "We've never had a problem with handicapped travelers," the spokesman said.

He added that he didn't see much advantage in having to bring in another tractor unit rather than another complete bus if a vehicle fails during a trip.

Mulhern is seeking a bus operating license from officials in Pennsylvania. He is working with State Sen. John Shumaker (R-Harrisburg), who sponsored legislation that would permit the state to grant such a license to Mulhern's vehicle. Mulhern hopes that the legislation will be approved this year.

Money is another problem. When asked if he had tried to contact venture capitalists for financial backing, Mulhern replied: "I'm naive. I don't know who to go to."

He said he believes that he can match intercity bus rates and that, although he will attempt to operate the first Amer-I-Can coach as a charter for the handicapped and their families, the coaches could be purchased by other carriers for the general public as well.

Mulhern has driven for 12 years for Trailways Corp., United Parcel Service, and for his current employer, which hauls mail for the U.S. Postal Service. Before that he was an Army Airborne courier.

He said that the inspiration for his invention was Vicki Snavely, a friend from Harrisburg who died five years ago. In high school, she regularly helped a wheelchair-bound teacher get to and from her car, an experience that led her to mention that it would be nice to get the disabled some better transportation, Mulhern recalled.

One day, as "I was driving to Pittsburgh, it hit me like a ton of bricks," Mulhern said. As he looked from the cab of the tractor-trailer he was driving into the side-view mirror and back along the semitrailer, he realized that "it could hold a lot of people."