Imagine for a moment that your summer vacation has arrived. You get an early start and hit the road at 6 a.m. By 4 o'clock in the afternoon, you've made good progress, you still feel fresh, and you'd like to keep going.

Sorry, that's not allowed.

However, you can get up at midnight, if you like, and resume your trip. Of course, you'll have to stop again at 10 a.m. Then you can try to sleep (you don't mind sleeping during the day, do you?) and rise at 6 p.m., when you can drive overnight until 4 a.m. the following morning.

This sounds idiotic. Yet it's only following the rules, established by the federal government 60 years ago, that regulate the work hours of the nation's 3 million commercial truck drivers.

One purpose of these rules was to promote safety by ensuring that truckers didn't drive too many hours and make fatigue-related errors or, worse, fall asleep at the wheel. But as the previous scenario shows, the basic hours of service rule -- 10 hours at the wheel followed by eight hours off -- creates a nightmare schedule for hundreds of thousands of truck drivers.

Despite these cumbersome restrictions, fatigue-related truck accidents are rare. According to the National Highway Traffic Safety Administration, fewer than 4 percent of such accidents involve large trucks. And truckers are by far the safest drivers on the road; their accident rate is less than half that of car drivers.

There is a general consensus that the rules -- written when little was understood about the rhythms of the human body -- are obsolete; Congress ordered an update four years ago. Yet some groups want the U.S. Department of Transportation, which already is 18 months behind its self-imposed deadline for a new regulation, to further limit the hours truckers may drive.

This flies in the face of both scientific research and common sense. Numerous studies have shown that the most important deterrent to driver fatigue is not limiting hours behind the wheel but providing sufficient time to rest. The American Trucking Associations support science-based rules that would ensure that drivers can receive at least eight hours of rest every 24 hours, on a schedule that best suits each one's own body's rhythms and needs.

This is a country that runs on trucks, which travel more than 190 billion miles every year and account for 81 percent of our nation's freight transportation revenues. Basing hours-of-service rules on hours worked rather than hours at rest and, therefore, reducing the hours that a truck driver can spend on the road will hinder highway safety, not improve it. Since the nation's merchandise must continue to move, more trucks would be needed, increasing traffic on already congested highways. Those additional trucks also would require more drivers, and in a tight labor market, trucking companies already have difficulty recruiting the 80,000 new drivers that are needed every year. Does anyone really believe a flood of inexperienced drivers will improve truck safety?

Finally, time is money. Requiring drivers to spend fewer hours on the road reduces productivity and will drive up the cost of delivery -- a cost that will affect nearly every product and service because trucks are such a large part of the delivery system in our country.

The nation's responsible trucking companies and drivers are committed to safety. The roads are where they work. The American Trucking Associations Foundation has participated in at least 10 fatigue-related studies examining driver fatigue and sleep-related issues. We launched a nationwide campaign to alert all motorists, not just truck drivers, to the risks of driver fatigue. We have distributed more than 1 million copies of our "Awake at the Wheel" brochure on how to avoid drowsy driving. We have disseminated public service announcements to more than 3,000 radio stations. We have trained thousands of trucking company safety managers, drivers and instructors about fatigue management.

American Trucking Associations members have worked for years to push the Department of Transportation to revamp the obsolete work rules that regulate our industry, and in coming months, we will introduce our own hours-of-service proposal, based on science, reviewed by fatigue experts and driven by safety.

We are asking that the department follow the recommendation set out by experts appointed by the secretary of transportation. These experts said it was vitally important that the department establish an advisory committee to thoroughly review the science before issuing a rule for debate. The industry will make sure its proposal is science-based and reviewed by fatigue experts. Those of us who make our living on the road expect no less from the department. We have also formally asked that it publish the science it will rely on for its proposal. This allows the public to review the science and comment on it.

Developing rules with no basis in science that tell able-bodied men and women simply to spend fewer hours doing their job would be counterproductive and would not improve highway safety.

The writer is president and CEO of the American Trucking Associations.