On Friday, I told you about my adventures in trying to find out what Virginia law says about snow tires.

At 4:31 p.m., an assistant county attorney had referred me to the Motor Vehicle Division, which did not answer its phone. On Monday, I resumed my quest by calling MVD and asking to speak to the person in charge in this area.

The operator said, "That would be Mr. Hensley at Tysons Corner."

Mr. Hensley was out for the day, and the woman who answered his phone expressed surprise that I would ask him what Virginia law considers a snow tire. "The State Police handle that," she said. "They set the rules."

A State Police sergeant first told me, "There is no state law on snow tires." Later he looked it up and said there is a state law that empowers cities, towns and counties to designate snow emergency streets and to enact regulations for punishing motorists who impede traffic on them as a result of their failure to equip their vehicles with chains or snow tires.

When I asked him what is considered a snow tire in Virginia, he said, "It has to be marked M/S, which means it meets the traction standards for mud and snow." I told him that radials on General Motors vehicles have for years been marked TPC (Traction Performance Certificate) followed by a four-digit number, and I asked whether these tires are considered snow tires in Virginia, as they are in Maryland and the District. c

He asked, "Are they marked M/S?" I told him they are not. "Then we do not recognize them as snow tires," he said.

I phoned Frank R. Faraone of the Washington office of General Motors and broke the news to him. "Your TPC snow tires are not considered snow tires in Virginia because they're not marked M/S," I said.

"Are you serious?" he asked. "I've never heard of any complaint about them from a Virginia customer."

"I'm serious," I said. "If you talk to Detroit about this, please let me know how you make out." He said he would.

Next I called Fairfax County Prosecutor Robert F. Horan Jr., whom I've always found knowledgeable and helpful. "I need to know Virginia's official definition of what is a snow tire and what isn't," I told him. "I'm getting different answers from county police officers and State Police officers. Can you look it up for me?"

He said he could and would, but almost two hours passed before he called back. He sounded weary.

"I've made a lot of phone calls since I last talked to you," he said, "but I have not been able to find any evidence that Virginia law says anything at all about what is a snow tire and what isn't."

He added, "The state law says the governing body of any county, city or town may, by ordinance, designate which streets shall be considered snow emergency routes, and may regulate vehicular traffic on those streets in the event of snow, ice, flooding and so forth. A driver can be charged with a violation if he or she obstructs or impeded the flow of traffic on such roads as a result of not being properly equipped with chains or snow tires. But that law does not define what a snow tire is."

En route to work, I kept wondering how Virginia motorists are supposed to know which -- if any -- radials will be accepted as snow tires.

Fortunately, when I got to the office there was a message that Fairfax County Magistrate Glen N. Drummond had called. When I called him back, he asked, "Have you gotten the snow tire information you were after?"

I told him what Bob Horan had said. "He's right," Drummond said. "The state law doesn't define what a snow tire is. It leaves that up to counties, cities and towns."

"You mean Arlington, Alexandria and Fairfax can all have different rules about which radials qualify as snow tires?" I asked.

"They can if they want to, and for all I know they do," he said. "Our law in Fairfax says that you can be cited for getting stuck and impeding traffic unless your car is equipped with adequate chains or snow tires.

"And of course the key word there is 'adequate," because if you get stuck, that's pretty clear evidence that your chains or snow tires were not adequate, isn't it?"

How interesting! One who drives through Virginia when snow threatens must wonder whether his radial tires are recognized as snow tires in each county, city and town on his route.

I think I prefer traffic rules that apply statewide.