Five weeks ago, reader Lynne Johnston, of Falls Church, suggested that the rush-hour restrictions on Interstate 66 inside the Beltway ought to be relaxed from HOV-3 (minimum three people per vehicle) to HOV-2. She noted that HOV-2 exists in other areas of the country and that, with the difficulty of finding fellow riders who have identical hours in the same part of town, the concept ought to be tried here.

A spokeswoman for the Virginia Department of Transportation expressed concern that if the restrictions were lowered, the highway might become too congested. She said that no traffic study had been done showing the impact of a reduction from HOV-3 to HOV-2 in the I-66 corridor, and that such a study was unlikely because it was too time-consuming.

Reader Jonathan A. Taylor, of Burke, then responded that no study is necessary. Anyone can see that I-66 is underused, he said. All one need do is survey the traffic, as he does, from the Metrorail line in the highway median. Most of the traffic consists of HOV violators, with relatively few vehicles carrying three or more people, he wrote. If all the vehicles ignoring the rules were removed, the road would be practically deserted. Therefore, he wrote, there is no reason not to try HOV-2.

Now, to its credit, the Virginia Department of Transportation has reviewed the situation and agrees with the readers that there is room to consider this change. "Your reader made such a potent point, it got us to thinking; it generated further consideration of the numbers we do have," said the department spokeswoman, Mary Anne Reynolds.

One recent department study shows that 381 vehicles per lane were using I-66 during peak morning rush hour. About 17 percent of those vehicles were violators (a number lower than reader Taylor observes), but the important point is that officials believe the highway can absorb more pool vehicles, up to about 800 vehicles a lane per peak hour.

The review prompted this letter from the department's chief traffic engineer in Northern Virginia: Dear Dr. Gridlock:

The suggestion that HOV restrictions on I-66 inside the Beltway be lowered from three to two persons for a period is certainly one Virginia Department of Transportation staff is willing to consider. With construction beginning next spring on HOV diamond lanes on I-66 outside the Beltway, VDOT is looking for every means possible to minimize delays on that already congested corridor.

A bit of I-66 history will remind readers why several agencies must concur in lowering HOV restrictions on I-66. The 1977 decision by U.S. Secretary of Transportation William T. Coleman, which allowed I-66 inside the Beltway to be built, specified that Virginia can change HOV restrictions "only with the concurrence of the U.S. Secretary of Transportation, the authorized transportation planning body for the metropolitan Washington area, and WMATA {Metro} . . . or by the U.S. Secretary of Transportation after consultation with these same parties."

And because any change in HOV restrictions would affect citizens of Arlington and Fairfax counties, their elected representatives should be consulted as well.

As one player in this large cast of I-66 decision making, VDOT is willing to initiate discussion on an HOV-2 demonstration project, which would run concurrent with construction of the interim HOV lanes on I-66. The first step will be to seek the blessing of VDOT's governing Commonwealth Transportation Board. Upon board agreement, VDOT will contact the other appropriate agencies.

I wish we could promise an immediate decision, but the ground rules on I-66 dictate a more deliberate pace. Regardless, VDOT will initiate the dialogue now. CLAUDE D. GARVER JR. VDOT District Administrator

This initiative means that the department could wind up testing the HOV-2 idea starting next spring. That's when construction also is scheduled to begin on a two-year project to build an extra lane for car pools on I-66 from the Beltway outward to Route 50. If such a test were successful, the entire expanded HOV corridor, inside and outside the Beltway, could become HOV-2.

Several questions come to mind immediately: Would HOV-2 siphon commuters off the parallel Metro route or add traffic congestion to streets inside the Beltway? Or would it promote the pooling concept by providing enough incentive that people who now drive alone would pair up, with spouses or neighbors, to get to work faster, thus taking cars off the roads? Regardless of any outcome, something may need to be done about enforcement to make the express lane concept more effective.

Readers Johnston and Taylor get a tip of the hat for making the suggestion, and the Transportation Department gets a Golden Hubcap award for caring enough to give the idea serious consideration. The Old Garage Attendant Ruse Strikes Again Dear Dr. Gridlock:

Your Nov. 2 column on auto theft really hit home with me. On Sunday, Oct. 28, my car was stolen from a garage in the 1100 block of 15th Street NW in the same manner as the Porsche in your column. {Editor's note: In that instance, a man pretending to be an attendant stood by an underground garage before opening hours, took the keys to a $40,000 Porsche from a would-be customer and, when the owner was out of view, drove away.}

My car was recovered later that night. However, I'd like to share the lessons about parking garages that I learned from this experience:

1. Know operating information about the lot or garage, such as the days and hours of operation and the rates.

2. If you are unfamiliar with the garage, look for signs posting this information.

3. Make sure you get a claim check. If the "attendant" can't or won't give you one, DON'T leave your car there.

4. Finally, look for other details, such as uniformed attendants, and the manner in which other cars are parked. If anything appears unusual or suspicious, drive on.

I hope these tips can help someone else. If I had followed them, I could have saved myself a whole lot of irritation. MICHAEL P. KENNEDY Vienna

Thanks for sharing that experience. Since the garage you mention is across the street from The Washington Post, your letter hits us close to home too.

Other Factors Spell No Joy for Wider Route 355 Dear Dr. Gridlock:

The completion of the work on I-270 has sure made my daily commute from Germantown to Andrews AFB much nicer. However, a serious bottleneck still occurs on northbound Route 355 at Watkins Mill Road when it narrows from two lanes to one lane.

Are there any plans in the near future to widen 355 to four lanes as far north as Route 118? CHARLES R. PEASE JR. Germantown

The short answer, apparently, is no.

John Clark, a senior Montgomery County transportation official, says the county understands the need for improvements in that corridor, but the problem is that it would not make sense to widen Route 355 at Watkins Mill Road because just a mile south of that point, the intersection of Route 355 and Montgomery Village Avenue (Route 124) is already at capacity. It can't take the extra traffic that would be generated by the widening of 355 northward. Further, Route 355 has to serve two needs: through traffic and local access. There are numerous driveways onto 355.

The state's long-term plan is to expand northward the Mid-County Highway, a four-lane, limited access road that would run parallel to Route 355 about two miles to the east. Mid-County now stops at Montgomery Village Avenue.

Extending it four miles northward, to Route 27, would cost about $60 million. There is money for planning, but none for construction. Even if the money were available, there are significant environmental concerns to resolve, Clark said.

"The immediate relief is transit and ride-sharing," Clark said. "There is bus service in that corridor. There's relief tomorrow if people want to sacrifice a bit of comfort and convenience for the general welfare. We can never put enough pavement in an urban area if everyone wants to drive alone; the automobile just takes up too much space."

Of course, finding other people who make the grinding commute from Germantown to Andrews might not be easy, Mr. Pease. Nevertheless, the county number to call to make car pool matches is 217-RIDE. Good luck.

Metrorail Has Good News for Big Spenders Dear Dr. Gridlock:

I recently discovered that the Metro station at National Airport has no Farecard machines that will take anything larger than a $5 bill. All I had was a $10 bill, and to get change I had to take a shuttle back to the terminal and then go back to the station.

I've seen Farecard machines elsewhere that will take up to a $20 bill. Since people arriving at the airport may well only have large bills, and it's probably the least convenient place in the entire system to get change elsewhere, why on earth does Metro limit its airport station to $5 machines? GEORGE WYETH Chevy Chase

Of the 432 Farecard machines in the system, Metro has only 27 that will take tens and twenties. Those have been placed at the higher-volume stations, such as Metro Center and Farragut West (about 25,000 boardings a day), rather than stations such as National Airport (about 5,000 boardings a day), said Metro spokeswoman Beverly Silverberg.

The good news is that Metro is replacing all its Farecard machines. Each new one will accept ones, fives, tens and twenties, as well as more readily accept legitimate currency and detect counterfeits. It's a $10 million project spread over four years. National Airport is scheduled to get the new machines in two or three months.

A reminder to send in your New Year's resolutions for local transportation officials: what you wish they would resolve to do, in a sentence or two.

Write (please don't phone) to DR. GRIDLOCK, The Washington Post, 1150 15th St. NW, Washington, D.C. 20071. Include your full name, address and day and evening phone numbers.