PAULA ANDREWS' 18-and 20-year-old sons never wore seat belts around their Springfield, Mass., neighborhood. But when they drove across the state line into New York recently, they buckled up because of the mandatory seat-belt law -- the first in the nation -- in that state. The crash occurred near Binghampton, and though the truck was a wreck, both young men walked away without a scratch. Gov. Mario Cuomo publicized this story the other day after Mrs. Andrews wrote the governor in praise of the statute. Replied Mr. Cuomo: "Frankly, I am not sure I have ever been more gratified in my brief tenure as governor than I was to read [your letter]." His enthusiasm was understandable. The controversial law had been in effect only two weeks and it was already saving lives.

It comes as no surprise that wearing a seat belt makes sense. Safety officials estimate that half the people killed in road accidents would have survived if they had been wearing the protective devices. Yet a large majority of Americans simply refuses to put them on. Some believe they're not necessary for short trips, which is wrong. Others say they're uncomfortable or dangerously restrictive. And the loudest resistance comes from those who protest that it's not the government's business to make them wear seat belts. But the New York experience has already shown that, once a law is passed, most people will comply. They will get into the habit of buckling up, and sooner or later it will be automatic -- especially for young people who grow up with the requirement.

There has been a concerted effort in state legislatures this year to enact mandatory seat-belt laws; the reason, in part, is the Department of Transportation's decision to require air bags in automobiles unless states with two-thirds of the nation's population enact seat-belt laws by April 1, 1989. Five states have now done so -- though only the laws in New York and New Jersey have gone into effect -- but others, including Maryland and Virginia, have rejected the idea decisively. Momentum is building, though, and legislators cannot fail to be impressed with statistics from 32 countries and seven Canadian provinces that show a sharp decline in highway fatalities following passage of these laws.

The government does have a stake in keeping down the medical costs of traffic injuries, but saving lives -- not money -- is the primary goal of seat- belt laws. It's an objective worth a little bit of government intrusion.