The Virginia state Senate has now joined the House in passing a mandatory seat-belt bill. Gov. Baliles voiced his support for such legislation when he took office in January, so the chances of its being enacted are excellent, although some differences between the House and Senate versions have to be worked out.

The major difference is that the House bill prohibits police from pulling over a car simply because someone in it isn't using his seat belt; the car must be stopped for some other reason. The Senate bill doesn't carry this prohibition. In most of the states where mandatory seat-belt legislation has been considered, legislatures have tended to make it as toothless as possible: small fines, no points on the driver's record, etc. It would be nice if Virginia decided to give its legislation at least a few molars by throwing out the house's restriction.

The main thing, though, is to get a law on the books. During the debate in Richmond this week, the senate chamber rang with oratory about the right of people to engage in conduct (not wearing their seat belts) that is dangerous only to themselves. By a 22- 17 vote, the senators refused to view such legislation as a first step on the road to tyranny, and passed a bill that will probably save several hundred lives every year and greatly reduce injury and suffering. All of these things cost the whole society dearly, not just the people who exercise their right not to buckle up.

Another thing about seat-belt legislation: It provides a good excuse. It gives drivers an excuse to ask passengers next to them to buckle up, a request they might otherwise hesitate to make. It gives a carload of kids who might think of seat belts as being slightly nerdy a good excuse to put them on: All can invoke the specter of a $25 ticket. If that's an incursion on civil liberties, it's one a lot of parents will be grateful for.

With the Virginia Senate's action, the great seat belt around this area comes nearer completion. In the District, a law took effect last December. The city is now seeking to educate people about it; sometime in June, the police will start handing out tickets. In Maryland a measure has cleared the Senate and is before the House judiciary committee. Perhaps soon, we'll hear the buckle click in Annapolis.