We all know how hard it is to find curbside parking in the District, particularly on weekdays in the downtown area. But apparently there is a way to reserve some of it for your exclusive use: Obtain a limousine and get the city to post signs in front of your business that reserve the space for limos only. Some residents don't believe that is quite right, and have complained to Dr. Gridlock. D.C. officials, asked about that, agree with the readers. Here are the concerns that initiated a look at limo stands: Dear Dr. Gridlock:

Everyone who drives to Georgetown knows how critical the parking problem is. I understand, and have no complaint with, the two-hour parking restriction that does not apply to cars with resident parking stickers. But I don't understand the signs posted in front of the building at 1219 28th St. NW in Georgetown. The signs display this notice: NO PARKING LIMOUSINE ONLY 7 A.M.-6:30 P.M. MONDAY-FRIDAY

I don't want to believe that someone was bold enough to install their own signs, nor do I want to believe that the D.C. government is beginning to establish reserved parking places for the stretch-limo set.

Can you please check with the D.C. government to determine if the signs are legally posted and what is the justification for them? JOHN F. JONES Washington Dear Dr. Gridlock:

I am curious as to what is required to have a space designated as a limousine stand. There is a three-space limo stand at 1708 New Hampshire Ave. NW that seems to benefit Anderson, Hibey, Nauheim and Blair exclusively. The closest hotel is more than a block away and across the street.

The three spaces are reserved on the street as a limo stand from 7 a.m. to 6:30 p.m., during which time a limo with personalized plates reading AHNB is usually parked there. As one who lives in that neighborhood and experiences the frustration of trying to find any unrestricted parking, I find it extremely unfair that a firm should have parking spaces reserved for its exclusive use, while residents of the area circle in vain looking for places to squeeze into.

Are there any requirements for designating a strip of parking as a limo stand? Or is it just a matter of what politician someone at Anderson, Hibey happens to know? LARRY ANTHONY Washington

Well, as Church Lady on "Saturday Night Live" might say, "Isn't that special!" Business folks, apparently, can reserve curbside space for their exclusive use by asking the city to install signs that reserve the spot for the business limos. Says Tara Hamilton, spokeswoman for the Department of Public Works: "We view a limousine stand as we would a tour bus or a taxicab stand, that these are areas where people would be picked up and dropped off."

What is a limo is a little less clear. Is a Mercedes-Benz a limo? A dark-colored Cadillac? And whose limos qualify? The spot in front of 1219 28th St. NW is in front of the Hotel and Restaurant Employees International Union. A union employee said the stand does not belong to the union, but to Seasons Travel, which is next door at 1207 28th St. NW. The union normally parks its limos (union limos?) in a nearby underground garage, according to a union employee, and those limos have been ticketed when parked in the curbside limo spaces "belonging" to Seasons Travel. Dr. Gridlock tried to contact Seasons Travel mid-week, but no one was home. Maybe they were off in their limo.

The law firm on New Hampshire Avenue NW, which occupies an elegantly renovated four-story building, issued the following statement about its curbside limo spaces:

"The signs were produced and placed by the District of Columbia. The District has full discretion over the use of the spaces in front of the building and apparently believed that to be the appropriate designation. There are 'No Parking, Entrances; No Parking, Loading Zones; and No Parking, Diplomats' signs at buildings all over the city."

A law firm spokesman said he did not know who had requested the limo parking, and declined to say why the firm needs such reserved parking.

D.C. officials could not find any paper work history on the signs at either location. After visiting the sites, the city decided that given the residential character of the general areas, the spaces now would be better used if turned over to the general public. The "Limo Only" signs will come down. That may take a few months, as the change must be processed and published in the D.C. Register, Hamilton said.

Hamilton said the city depends on residents to be its eyes and ears and will visit any other such "Limo Only" stands to determine whether they still make sense. Write to the Bureau of Parking Services, 65 Massachussetts Ave. NW, Washington, D.C. 20001. Raised Exhausts Urged for Buses Dear Dr. Gridlock:

Thanks for the recent information about bus fumes. I, too, have been overwhelmed by them and suggest a fairly simple means to reduce the direct impact of the fumes: Buy buses that exhaust out of the top, like many tractor-trailer trucks. At least one brand of transit bus is manufactured this way.

I used to bicycle in a midwestern city that had a mixed fleet of buses, and following a low-exhaust bus was terrible. Unlike the car driver, a bicyclist keeping up with traffic is gulping down great amounts of air into pockets of lung. ALAN ERNHART Annapolis

It costs enough that the largest bus provider, Metro, isn't planning on buying any. Metro has one bus in its fleet that has top exhaust, but that was manufactured in the 1970s. The agency hasn't bought any more because there is additional purchase and maintenance expense for the extra exhaust piping, which has to run past and be insulated from the air conditioning and heating units.

Beverly Silverberg, a Metro spokeswoman, said she believes that the raised exhaust pipe makes not a significant difference because the particulates settle downward anyway.

The Art of Transportation Compromises Dear Dr. Gridlock:

Thoughtful letters by two of your readers in your Jan. 25 column illustrated the plain truth: Building roads in a democracy isn't easy. On one hand, you have an Arlington reader opposing the idea of more HOV {bus and car pool} traffic coming through her community. On the other, you have a Silver Spring resident complaining that there are HOV lanes on Interstate 66 at all, because they parallel a Metro line.

Remember, the only way Virginia was allowed to complete I-66 inside the Beltway was to make it HOV during rush hour AND commit to completing Metro in that corridor. Like most roads in a democracy, this one was built on compromise.

Mr. Bailey of Silver Spring believes mass public transportation is the answer. Most transportation planners would respectfully respond that no one transportation mode is suitable for everyone. The best transportation systems give commuters choices that recognize their varied commuting patters and destinations. That means rail and bus service for some, HOV lanes for others -- helping to clear the conventional lanes for individuals such as Mr. Bailey, who has a Silver Spring to Tysons commute and truly can't take advantage of the faster, cheaper modes.

Thank goodness for the million-plus commuters in the Washington region who travel to work in car pools, van pools and buses! Can you imagine our roads if they were on them, too? MARY ANNE REYNOLDS Virginia Department of Transportation Dear Dr. Gridlock:

I am responding to several residents who wrote to you last week, stating that there is no one for them to car pool with. I would like to invite them to join the Ride Finders Network. This is a free ride-sharing service sponsored by the Metropolitan Washington Council of Governments, and state and local governments.

Ride Finders has 16 offices to serve Northern Virginia, suburban Maryland and the District. We have 15 years' experience putting people into car and van pools, and our database currently contains the names of more than 10,000 people who are looking for a pool of new riders.

So, for all you frustrated commuters who wish you had someone to share a ride with, please contact us at 202-783-POOL and let us help you. More than 500,000 Washington area residents share rides to work, about a quarter of all commuters here. Many of these have been helped by Ride Finders. Give us a call before deciding that car pooling doesn't work.

Dr. Gridlock appears in this section each Friday to explore commuting matters. He'll try to find out why bad situations exist and what is being done about them. You can suggest topics by writing (please don't phone) to DR. GRIDLOCK, The Washington Post, 1150 15th St. NW, Washington, D.C., 20071. Please include your full name, address and day and evening phone numbers.