Government regulations sometimes have a ripple effect on private commerce. If the government sets limits on the length of cargo trucks, the truck manufacturers squeeze space from the cabs -- to make more room for cargo. Then the government starts looking at safety regulations on the size of the cabs. That's what the Federal Highway Administration is studying now.

Every state has put some restriction on the length of trucks, most of them 55 to 65 feet, with the longest allowable length set at 75 feet. As the size of trucks has been forced down, the vehicle manufacturers -- wanting to keep the largest possible space for cargo -- have reduced the size of the cab, where the driver sits. This led to complaints from driver organizations who contend the smaller cab leads to fatigue and may cause more accidents.

Government regulators also have weighed in, pointing out that smaller cabs could make the truck harder to steer and put excessive weight on the front tires.

In the Federal Register, they recently laid out the situation and its proposed solution a formal rule-making procedure to determine "if there is a serious safety problem related to cab size."

The federal officials also plan to explore whether the problem should be resolved by voluntary or compulsory rules.

The highway administration made no bones about who would end up paying for any changes required to meet new cab size standards -- and in so doing identified another of the regulatory ripples.

Initially, the agency said, the manufacturers would have to finance redesigning and retooling of the trucks. But they, in turn, would charge more to the truckers for vehicles with less cargo space due to enlarged cabs. The truckers, in turn, would have to hire more trucks and drivers to make up for the loss of space and increase of vehicle expense.

"All these factors," the agency concluded, "could increase shipping costs and eventually result in consumer price increases for all items carried by truck."

The proposed rule-making is set for September. For more information contact Gerald J. Davis, Bureau of Motor Carrier Safety, Federal Highway Administration, 400 Seventh Street SW, Washington, D.C. 20590, or phone 426-9767.