The American Automobile Association has been reminding government officials that parts of our interstate highway system are now 20 years old.

Some segments of these superhighways may be relatively new, but others are in need of maintenance or even major upgrading that will permit them to meet modern safety standards.

As part of its plea for sale interstate highways. AAA points out that in the years ahead "there will undoubtedly be increased use of smaller cars and larger, heavier trucks," AAA says this "mix" of vehicles will cause "complex safety problems" - an observation that could rank as the understatement of the month.

There has long been statistical evidence that as the size and weight of a vehicle go down, the risk of injury to its occupants goes up.

When a small car is in collision with a big car, the odds are that the smaller vehicle will sustain more extensive damage and that its occupants will suffer greater harm than the occupants of the larger vehicle.

Now, at a time when truck sizes are increasing, we're going to be switching to smaller and lighter family cars - and the consequences are going to be deadly.

True enough, highways that are properly maintained will help. Highways that are redesigned to be as safe as we know how to make them will help. But nobody has yet learned how to redesign the nut behind the wheel. We're going to continue to have collisions, and if anybody has put forward a solution to the "complex safety problems" caused by a mix of bigger trucks and smaller family cars. it has escaped my notice.