Despite nearly 10 years of government pressure to make railroad tank cars safer, they could be "at least four to six times safer than they are today," according to the head of the National Transportation Safety Board.

James B. King opened three days of hearings on rail safety and the transportation of hazardous materials with that statement, and add:

"Every month in which unprotected tank cars ride the rails increases the chances of another catastropic hazardous materials accident."

King said the necessary safety devices could be installed on the tank cars in question "by Christmas 1978 - not in four years. (as prescribed by law)"

But at least one industry spokesman said that it would be impossible to retrofit all of his firm's jumbo cars by the end of the year because only a small amount of cars can be removed from service without creating "serious economic dislocation to the nation."

Jack R. Kruizenga, president of the Union Tank Car Co. of Chicago, said his firm has under construction a $9 million plant in Cleveland, Texas, that will be used exclusively to retrofit some 6,000 jumbo tank cars.

"When we get on stream on July 1 of this year, as now planned, we will produced at the rate of 45 cars per week," Kruizenga said.

He said the retrofitting will cost his company "more than $10,000 per car, or $40 million for our fleet of 4,000 cars."

Of the approximately 20,000 jumbo tank cars on the rails - they have a capacity of 33,000 gallons, three times the cars they replaced - "to date only a few dozen of them have been modified" with recommended safety features, King said.

To demonstrate how easy it is to retrofit the tank cars with the protective devices, the NTSB ran a demonstration on a rail car mockup outside the building in which the hearings were held.

In seven and a half minutes, a handful of workmen replaced the car's traditional coupler with a safer model and, in another 30 minutes, welded a safety shield at one end of the tank.

"We intend to show that simple safeguards, which can be quickly installed, will reduce the danger of the most common type of these hazardous material accidents by more than 85 percent," King said.

To support his thesis, King showed films of rail car collisions with and without the safeguards attached to the cars.

The NTSB hearings also heard from five victims of hazardous rail disasters that date back almost a decade.

The five described their personal horror stories to board members. A huge color photo of a fireball steming from a tank car explosion was on the wall behind them. In addition, the board showed films of some of the disasters discussed, and released data showing that derailments involving hazardous materials have caused 65 deaths since 1969, and that rail incidents involving hazardous materials are on the rise.

Berger Howard of Dothan, Ala., broke into tears when he began to describe how a 21-year-old companion died after they had driven through Youngstown, Fla., right after the derailment there last February.

And Mrs. Linda Stevens of Curbank, Mont., told how a derailment and explosion there in 1976 "left emotional and physical scars" on her town, and resulted in the death of her father.

She said that officials of the Burlington Northern Railroad said her father was old, and had lived his life. "They would only pay for things of marketable value," she said, adding that many people lost items of personal value, but were'nt reimbursed.

The NTSB is charged with investigating all transportation accidents with fatalities, but does not have the authority to required changes. The task falls on the Federal Railroad Administration.