If you are planning any long-distance automobile trips, the best way to pace yourself, according to government-sponsored research, is to take 20 to 30-minute rest breaks after every hour and a half to two hours of steady driving.

Without such breaks, a driver can begin to show fatigue and hypnotic effects: the inability to recognize the speed at which the vehicle is traveling, a trance-like state of mind and hypnagogic hallucinations -- like seeing imaginary things on the road.

You may ask what this kind of information is doing in this column. The answer is that it, along with a good deal more on driving, appeared in the Dec. 15 Federal Register (page 82284). The issue being discussed was a petition before the Federal Highway Administration (FHWA) by owner-operator truck drivers who, among other things, wanted the federal government to let them drive more hours.

The FHWA notice includes, in fact, almost more than you may want to know about driving and fatigue.

It's no surprise that "sleep was a factor in from 13 to 20 percent of [highway traffic] accidents involving fatalities." But it's in the discussion of fatigue and its effects that the notice holds a reader's attention.

For instance, the notice says that the heart beats faster when an individual is fatigued. A recent study found that the heartbeat of truck drivers increased as they drove over a monotonous portion of a 364-mile stretch of highway. Then, when the driver "inadvertently" ran over a raised lane in the roadway, his mind was "realerted" and his heartbeat "decreased substantially," according to this study.

Then there is the decline in peripheral vision. Another study cited in the notice found "the peripheral retina is more impaired by stress arising from fear, fatigue and visual noise" than is that part of the retina that takes in what is straight ahead. It is hypothesized that with the eye less able to take in visual matter from the periphery of the road traveled, "the driver cannot maintain the same degree of control of the vehicle, in terms of velocity and road position, as could be maintained while not fatigued."

The fatigued eye also tends to become fixed on what is directly ahead, a situation that brings on drowsiness or even sleep when the driving becomes monotonous -- as often is the case in long-distance trips.

At this point, the phenomenon of hypnagogic (caused by drowsines) hallucination comes into play. Thirty-three long-haul truck drivers, interviewed during one study, reported experiencing these hallucinations, the notice said, "while none of a group of 20 local [or short-haul] truck drivers had done so."

For those who did see things, the sightings were so real that they often made an emergency stop, sometimes driving off the road, without recognizing that the situation is not real.

The FHWA's notice so strongly ties fatigue to accidents that it should come as no surprise that the petition by the independent truck owner-operators was turned down. The current federal rule, limiting a driver to 10 hours of driving followed by eight consecutive hours off, was upheld. The owner-operators proposed that they be permitted to drive for "not more than 12 hours in one 24-hour period. . . .""

Opposition came from a variety of elements within the trucking industry. Of 700 commenters, 94 percent opposed the idea -- most of them drivers, according to the FHWA. Most of them worked for companies which, they said, would go to the expanded hours if the owner-operators were allowed to.

In support of their own proposal, owner-operators claimed they needed the expanded hours "to protect their investment." They added an important footnote to this aspect of government regulation: that without such a changed in the rules, "the only way they could stay in business was to violate the [Department of Transportation] rules . . . the extra hours would allow a trucker to do legally what he is now doing illegally, as there is a minimum income that must be made in order to survive."