If you spend a considerable amount of time riding trains and buses between Washington and Richmond, you are struck by the great wisdom of Yogi Berra.

Yogi once said, or so it is alleged, "No one goes to that restaurant anymore 'cus it's always so crowded."

Right, Yogi, and it's the same with buses. No one rides them for the simple reason they are swarming with humanity.

But trains? Trains are something else.Did you ever talk to anyone who doesn't love to ride trains. Why shouldn't they? They're always at least half empty.All the people who love them are packed onto buses and airplanes or in cars fighting the traffic.

There are six trains a day between Richmond and Washington and the casual observer, this regular rider, would have to say that Amtrak under Paul Reistrup has made them a dependable pleasure to ride.

Three of them are Florida trains whose older, heavy cars can seduce you into believing you are rolling along in the last, well-preserved Packard. The other three use Amtrak's new light-weight cars that give you the ride of a new Ford or Chevrolet, actually a better ride at that.

You can usually set your watch by the Amtrak service between the two cities. The morning train that glides out of Richmond at 8:35, stops briefly at Fredericksburg at 9:26, Alexandria at 10:15 and slips through the tunnel into Washington by 10:35. Unfortunately, most people along the way appear to be using the service for time-keeping rather than transportation. Competition for seats is light.

That, of course, is the problem with Amtrak. Because Americans and their political representatives love trains so much, we are operating an expensive service in the face of light demand.

It creates a financial problem. The non-riding taxpayer pays more for a trip between Richmond and Washington than the passenger, who pays only $10.50 for a coach seat and $14.75 for a parlor car seat or, on the Florida trains, the splendor of a private compartment.

Buses are another story. They are countless in number as they run up and down Interstate 95, also on time, but at a profit for their owners and with no splendor at all for their passengers.

Greyhound and Trailways are not in the snob appeal business, and, as a result, none of us, we are happy to say, knows any of the millions who travel with them.

The trouble with the buses is they are no fun. There are no private compartments, no possibility of folding down a bed on a long trip, no food, no bar - nothing but crowded seats carrying you from one seamy station to another.

We keep our trains running in the belief that the gasoline pumps will eventually run dry and we will need the railroads again to replace the automobile for inter-city transportation. It is proving to be an expensive backup system.

Meanwhile, the buses are running everywhere at a profit, but are not making an appreciable dent in the automobile traffic that is contributing so much to a ruinous export of dollars for petroleum.

So why not experiment with the bus? If hordes will pay modest prices to ride four abreast in an open coach over the interstates, how many people will pay more, even twice as much, to ride in two abreast private compartments?

Could not buses so equipped and offering a few multiseat conference compartments make a dent in the business travel market between Richmond and Washington, and in the intensely traveled market to the northeast?

Government at all levels would have to play a major role to make it work. It would take exclusive bus lanes, mini-depots in suburban and downtown office locations, new traffic laws to give buses the right lights by bus drivers and relaxed regulation to encourage new entrants into the intercity bus business.

These governments already have an enormous investment in the roads that buses use, why shouldn't they try to squeeze more out of this investment with an expanded bus market?

It may stamp out what is left of the trains, but only a handful of us will really care.