A western Maryland automobile testing firm, which drives cars hundreds of miles of examine what wear and tear does to auto components, has for three years had permission to travel up to 70 m.p.h. on some interstate highways in Maryland and West Virginia.

The little-known special exemption, which was granted to Hercules, Inc., by Maryland Gov. Marvin Mandel in 1974, came into public view recently when a driver for Hercules accidentally struck and killed a pedestrian crossing 1-70 near the Frederick-Washington County line.

State highway officials have absolved the driver of the Hercules car, 21-year-old John L. Treadwell, of La Vale, Md., of any blame for the midnight accident which took the life of John H. Temple, 30, of Frederick.

The police report on the April 2 incident does not contain any notation of the speed Treadwell's car was traveling, an indication, according to one officer, that speed was not a factor in the crash.

"It's my understanding he [the pedestrian] was running and ran out in front of the vehicle at midnight," said Robert H. richardson, the manager of testing analysis of Hercules.

The accident was the first fatality involving a Hercules car in Maryland, according to Richardson.

During an interview yesterday, Richardson added taht without the special highway exemption, which allows his drivers to imitate the 60-to-70-m.p.h. highway speed at which he says most drivers travel, his company's tests would be virtually worthless.

At present, the only vehicles in eithe rstate permitted to exceed the 55-m.p.h. limit are emergency vehicles such as police cars and ambulances which may exceed the limit only in emergency situations.

Without his company's exemption, Richardson added. "We would probably go out of business. There would be no way to do what the industry needs."

"We're a consulting engineering testing lab," he said. "We're looking for the truth. We have to this under real world conditions . . .If you're trying to evaluate what a product will or will not do you have to travel at the speeds people drive."

On highways, Richardson said, those speeds are most often between 60 and 65 miles an hour. The high speed driving, he added, "is only a small portion of what we do" to test such things as tire wear and fuel economy.

Word of Gov. Mandel's exemption for Hercules and its Allegheny ballistics Laboratory testing section came to the company in the March, 1974, letter from Col. Thomas S. Smith, the superintendent of Maryland State Police. Along with the permission to travel up to 70 m.p.h. the maximum highway speed permitted in Maryland before speed limits nationwide were reduced to 55 m.p.h. - came regulations governing just where the Hercules cars could operate and how they should be marked.

The letter restricted the Hercules vehicles to 240 miles to Interstates 70 and 81 and U.S. Rte. 40, highways stretching roughly from Cumberland to the outer baltimore suburbs.

The Hercules tests are performed under contract for such firms as tire manufacturers, glass manufacturers, and some governmentat agencies. Richardson refused to identify any of his firm's clients by name.

efore Col. Smith actually gave Hercules permission to drive up to 70 m.p.h. - similar permission already has been granted by the head of West Viginia's Department of Highways - Sen. Jennings Randolph (D-W.Va.) wrote a letter to Hercules Manager W.J. rue indicating that he favored the idea of an exemption.

Randolph, who was then chairman of the Senate Committee on Public Works, wrote. "I was pleased to read that the State of West Virginia has granted your request for an exemption, and I hope other states will be encouraged to follow suit . . ."

"The . . . research activities you conduct are important in implementing federal policies and regulations and I would hate to see the employment generated by those activities reduced or lost," Randolph's letter continued.

Hercules executive Richardson said yesterday that a loss of the special exemption would mean a loss of about 150 jobs in the Cumberland, Md., area where the firm is based. Unemployment there is already at about 18 per cent, he said.