Dear Dr. Gridlock:

You wrote about the work underway to add an additional lane to the inbound Roosevelt Bridge, and how that is supposed to cut in half the amount of time it takes to get across the bridge in rush hour. But without improvements on the other side of the bridge, doubling the average speed on the bridge only means that you'll get to the backup on the other side of the bridge twice as fast. Big Deal. G.R. ANGELL McLean

That's a fair observation. Allow the doctor to present a fuller picture, as explained by Rep. Frank R. Wolf (R-Va.), who pushed for the change.

The widening of the bridge from three lanes to four inbound is expected to make a big difference in getting into the city because the bridge itself is now the bottleneck.

Four lanes (two from Interstate 66, one from Route 50, one from the George Washington Memorial Parkway) now merge into three on the bridge. The wait to make the merge clogs up the parkway and sometimes prevents through traffic from proceeding down the parkway toward the 14th Street bridge. The merge also causes lane changing that leads to accidents. There are multiple choices immediately on the city side of the bridge: the E Street Expressway, I-66 past the Kennedy Center to the Rock Creek Parkway, Constitution Avenue, 23rd Street, or through West Potomac Park to Independence Avenue.

"Experts feel it will really make a tremendous difference" to add the extra lane, Wolf said. Average rush hour speed when the widening is finished next spring should increase from 15 mph to 33 mph.

The additional lane is part of a parkway improvement plan that includes an extra lane from Spout Run onto the parkway (eliminating the need for a police officer to direct merging onto the parkway from Spout Run) and a new stacking lane providing access to the Roosevelt Bridge. Those projects should be completed in 1992, Wolf said.

Double-Parking Nightmare

Dear Dr. Gridlock:

The corner of 14th Street and Pennsylvania Avenue is a nightmare every morning for thousands of folks who drive in from Virginia. The biggest problem is that trucks park, and double park, in front of the J.W. Marriott Hotel at that corner during rush hour, forcing three lanes of traffic into one or two.

There seem to be no restrictions whatsoever on deliveries to the hotel and to the National Press Building (14th and F streets), and no police to get them out of the way. It seems outrageous that deliveries to the hotel are not restricted to the midnight to 6 a.m. period or something like that, and prohibited between 7 to 10 a.m. MICHAEL GETLER Alexandria

Illegal parking during rush hour, along with intersection blocking, are probably the two principal causes of gridlock in the city. In this case, there is no parking or standing along 14th Street at this location during rush hours, and that means between 7 and 9:30 a.m. and 4 and 6:30 p.m., but apparently there is an enforcement problem here.

The city does not want to ban deliveries during the day, nice as that may be for motorists, because that's when most commerce traditionally takes place, and when stores are staffed to receive deliveries, according to a city government spokeswoman, Tara Hamilton. "The balance between motorists and commerce is part of the balancing act that urban areas are involved in," she said. "Our busiest time of the day is probably between 11 a.m. and 1 p.m. because that's when most of the deliveries are."

Hamilton said it sounds as though there is an enforcement problem at this location during rush hour, and she would alert the Department of Public Works ticket writers to look into the problem.

Barton Parkway Changes

Dear Dr. Gridlock:

Currently the Clara Barton Parkway becomes one-way towards the District at 6:45 a.m. I would like to suggest that it be made one way beginning at 6:15 a.m., along with Canal Road going into D.C.

The commuter traffic, particularly those who start work at 6:30 a.m., starts building up around 6 to 6:15 a.m. V.B. PANDIT Potomac

Within days of your letter earlier this month, the city and the National Park Service changed the beginning hours for one-way inbound traffic flow on the Clara Barton Parkway (from Glen Echo) and along Canal Road in the city. The one-way direction now begins at 6:30 a.m. and ends at 10 a.m. Officials believe this is early enough, but the city is considering a change to the one-way outbound hours. Currently they are from 4 to 7 p.m., but because of the volume of traffic, the city may start the one-way direction outbound as early as 3 p.m.

Route 48 Construction

Dear Dr. Gridlock:

This is not of the local area, but I'm sure is of interest to many readers who go through Maryland on one of the major routes into the Midwest.

I've seen much construction under way on U.S. Route 48 between Hancock and Cumberland, Md. Can you find out when the final section of U.S. 48 will be completed?

I use that highway quite often and the construction areas have had terrible traffic problems as the vehicles slow to a "snail's pace." Trucks using the road can't traverse the mountains quickly, and traffic behind the trucks comes to a standstill. Any help you can provide would be appreciated. EUGENE BAUER Alexandria

What you are seeing is a 19-mile construction project, just east of Cumberland, that is the last segment of U.S. Routes 40 and 48 to be converted from a two-lane road into a divided four-lane road built to interstate standard. The project began in 1987 and is scheduled to be completed by September 1991, or possibly as soon as June 1991, if weather is good. It is taking more than four years to finish the work because of the mountainous terrain and longer winter in that part of Maryland.

Pohick's Pothole Problem

Dear Dr. Gridlock:

The standard Virginia Department of Highways response to pothole aggravations seems to be a restatement of motorists' responsibilities to report potholes, offering rationale to the effect that "we {the department} cannot drive and inspect every road every day . . . . "

After just so many times, responses of this nature tend to be cop-outs.

There is a nasty, wheel-wrenching, tire-shredding pothole on Pohick Road, about a mile north of the Pohick Road-Route 1 intersection in Fairfax County. The pothole is about 12 to 14 inches across and appears to be four to five inches deep, with sharp edges. It has been there for nearly nine months. I wonder why I should have to report it.

Is not this section of Pohick Road the monitoring responsibility of several echelons of VDOT management? Surely someone's job description or responsibility includes Pohick Road. What is your OWN system for reporting and repairing potholes, VDOT? Are state and county police requested to report potholes they notice? If not, why not?

We motorists need to start getting some accountability from the INDIVIDUALS who are salaried by our tax dollars. BILL FLORENCE Springfield

The Virginia highway department does have its staff monitor the roads regularly and report potholes, according to spokeswoman Joan Morris. State and county police also routinely report potholes. In addition, many homeowner associations spot potholes and provide somewhat comprehensive lists to the state. That said, it is not clear why that pothole has existed for nine months, Morris said. It had been temporarily patched a few weeks ago, she said, but the filling came out. It is now being permanently patched. For more information on potholes, including the state's brochure on facts and efforts, you can call the department's local public affairs office at 934-7350.

Braddock Road Widening

Last week, the doctor neglected to provide the new projected date for the completion of the widening of Braddock Road in Fairfax County, between Guinea Road and Roanoke Lane, near George Mason University. The lastest projected completion date is by mid-October.

Turning Off Pollution

Dear Dr. Gridlock:

May I suggest a simple measure to help reduce air pollution, fuel consumption and vehicular noise that all contribute to Washington's summer misery index: Turn off idling buses.

Tour buses, city buses, commuter buses. They are all over Washington, sitting sometimes for hours, unoccupied, with their engines running. The law requires them to be off. The environment begs for it. And we pedestrians are almost dying for it. Police, enforce the law!

Make bus drivers shut off those engines. Tickets would increase our already legendary traffic fine revenue for the city and enforcement would not add to the police burden since buses are most often idling around tourist sites patrolled by the Park Service and Capitol Police, who, instead of walking by these pollution factories, could be directed to take a moment to enforce the District's law (to mention that this might just help save the very monuments that these officers are guarding is beyond the scope of my simple plea, but should weigh in for enforcement.)

Gentlemen, stop your engines! C.R. KLEIMAN Washington Emergency Metro Intercoms

Dear Dr. Gridlock:

I'm curious about an emergency "intercom" that I see at the Federal Triangle Metro stop, attached to a pillar at the platform. I would think that this device is just what's needed in a variety of circumstances, such as medical problems, individuals on the tracks, other disturbances.

Yet I've not seen this intercom at other stations. Are they standard or not? Useful or not? Visible or not? Thanks for any insights. RUTH SALINGER Bethesda

The speakers connect the user with the station manager's office, and are helpful in alerting Metro personnel to emergencies.

They are at every station, on the pylons that have the station name on them, according to Marilyn Dicus, a Metro spokeswoman. They are not necessarily on every pylon though.

At McPherson Square, where the photo was taken, there are four emergency speakers and 12 pylons. They are sometimes at the back of the pylon, and are not readily seen. Metro is considering flashing red lights or other means to make them more visible.

Dr. Gridlock appears in Metro 2 each Friday to explore what makes it difficult to get around on roads. We'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.