Dear Dr. Gridlock:

When is the interchange construction of Route 50 (John Hanson Highway) and the Beltway going to be finished? The construction is causing a lot of headaches. DERRICK C. CEPHAS Glenarden

Better stock up on aspirin, Derrick. It looks like two more years before that work is done. The interchange is one of the last pieces of a mammoth undertaking to convert the four-lane John Hanson Highway into a six-lane interstate highway, from Rowe Boulevard in Annapolis to just inside the Beltway.

Other segments of the project are scheduled to be completed sooner. Moving from Annapolis toward the Beltway, the finish dates are as follows:

From Rowe Boulevard to Interstate 97, mid-1991.

From I-97 to the Anne Arundel County line, 1993.

From Anne Arundel County line to Route 301, including the Route 301 interchange, 1993.

From just west of Route 301 to just west of Route 197, mid-1991.

From west of Route 197 to just east of Lottsford Vista Road, end of this year.

From east of Lottsford-Vista Road to just west of Whitfield Chapel Road, spring 1992.

From just west of Whitfield Chapel Road to just west of the Beltway, late 1992.

The Route 410 interchange, spring 1991.

If there's any consolation to the long lines of rush-hour pain between the barriers, it is that something is being done to make that corridor easier to navigate. This is a result of Maryland's aggressive posture in obtaining federal interstate money. Your fellow commuters in Northern Virginia are seeing nothing on that scale to improve their lot. Virginia officials are taking a more aggressive posture now in obtaining such funds, but for roads such as Interstate 66, that is years behind the need. Unfinished Business Dear Dr. Gridlock:

How does the D.C. government cooridnate street repairs with utility diggings? For example, about a couple months ago, the city (according to its sign) spent $1 million for street and sidewalk repairs around the 1000 block of Vermont Avenue NW.

The repairs included removing the top surface and resurfacing the street, installing new curbs and installing new sidewalk pavers. About a week after this was done, the utility company moved in and removed some of the sidewalk and street paving. They did backfill the street surface, however, certainly not in A-1 condition. I can visualize the potholes that are going to appear.

What is the net effect? A lot of taxpayer dollars spent on replacing the street surfaces.

Is there logic behind this? DAVID L. PRYOR Washington

In theory. The city tries to coordinate utility work with street repairs to avoid just such a situation. That's why recent downtown improvements in the 14th Street corridor and on New York Avenue took so long. In this instance, the street disruption you are seeing is not as serious as it seems because Vermont Avenue has received only the road base. The final coat of asphalt will be applied after the Potomac Electric Power Co. work, which is supposed to be completed at the end of this month. You can tell when a road is not completed when you see the manhole covers well above grade.

As for the sidewalk cut at Vermont and L NW: Oops! Pepco's request came through the pipeline after the sidewalk was finished, according to Tara Hamilton, spokeswoman for the D.C. Department of Public Works. Said Hamilton: "We would have preferred if they had plans and design ready before we started putting down the surface, but it didn't work out that way. They {Pepco} will bear the cost of the total restoration of the sidewalk. It should be finished by the end of October."

Try Using the Ashtray Dear Dr. Gridlock:

While canoeing last summer, a cigarette smoker ahead of us carelessly tossed a butt out of the canoe. When we came abreast of where he had thrown it, a small fire had started in the reeds by the side of the river. And smokers say I'm silly for being afraid of cigarette butts being thrown out of moving cars. Just because it leaves your fingers doesn't mean it is not lit anymore. MARY S. O'BRIEN Waldorf

Just when you thought you'd heard it all . . . . Not to excuse this, but a canoe may not be equipped with an ashtray (the water should do). There's no excuse for flipping a cigarette out of a car, and it's a mystery to the doctor why people do it.

Two-Way Reports Needed

Nearly two years ago I began a "reverse commute" from my home in Washington to Fairfax County. In this short time, I contend there is no such thing as a reverse commute anymore. Granted there is not as much traffic going west on I-66 in the morning as there is coming east (just the opposite in the evening), but there are constant traffic jams near the Sycamore Street exit and Dulles Toll Road. A suggestion:

Why can't the radio traffic announcers talk about the congestion on our side of the road? The only time they mention it is if there is an accident. I can take a different route if I know there is a traffic tie-up, but I need to know before I reach it. GAIL S. KEARNEY Washington

The airborne troops probably have their hands full with the more congested, rush-hour arteries. But they can note the request.

Two Tales of Bicycling Dear Dr. Gridlock:

Bicyclists need to remember one rule above all others: RIDE AS IF YOU WERE INVISIBLE! The vast majority of motorists are oblivious to their surroundings. Considering the rate at which they rear-end each other daily on the Beltway, does anyone really think the typical motorist pays much attention to cyclists?

If you consider yourself an "invisible rider" and continually monitor situations as they develop around you, planning contingencies in case someone opens a car door, turns in front of you, or runs a red light, you switch the survival odds tremendously in your favor.

About five of my daily 31 miles bike commuting are on the Rock Creek bike path, and the invisible rider theory works there as well. Most joggers "cut" every corner on the bike path with never a thought for other users, so I plan for their inattention.

I ride fast and aggressively, but predictably and defensively. It's known as "effective cycling," after the book and course by that name, and it works. In nearly 30 years of driving, I've never had or caused an accident, and in over 21 years of bicycle commuting, I've had one minor accident with a car (16 years ago).

If I'm hit tomorrow, it doesn't mean my theories are wrong; it just means, like everything else in life, there is some luck involved. But for the most part, you make your own luck.

A person on a bicycle is the most efficient moving thing on earth. Commuting or running errands by bicycle allows you to get "free" exercise when you have to be going somewhere anyway. And most of all, it's fun. DENNY FREEZER Silver Spring

Thanks for the tips, Denny. Motorists would be well advised to drive defensively too. Now, the next letter comes from a lady with an experience with a different sort of bicyclist, the exception, we hope: Dear Dr. Gridlock:

On Sunday, Sept. 16, my car, my passenger and I were attacked by two bicyclists as I drove south on 14th Street NW.

Midway through this nasty incident, I realized that I was unable to identify my two attackers, since their bicycles did not have tags and they were unlikely, in their vicious frame of mind, to give me names or addresses.

As a result of this very bad experience, I am convinced that bicycles, like all other vehicles, should be registered and carry tags, and their riders, like all other vehicle drivers, should carry identification cards.

Both bicyclists were riding in my lane ahead of me, randomly riding at first single file and then abreast across the lane (My passenger noted that this is illegal in her city, Madison, Wis.)

I moved well to my left, passed them, and pulled ahead. To the best of my knowledge, I came no closer to either of them than I would have come in safely passing any other vehicle.

As I stopped at the intersection ahead, one bicyclist roared up to my passenger's side and began pounding on the window, screaming at me about his rights.

Not getting the response he wanted, he rode to my side, snatched open the car door (another lesson learned) and struck me hard with his closed fist.

Meanwhile, his companion had flung down his bicycle in front of my car, and was shrieking profanity at me.

Eventually, the car behind me created a space, and I backed up and away from the two. Though the episode took no more than a few minutes, its irrationality and violence were stunning.

Bicycle terrorists such as these will not want to be identified by tags or registrations, which is all the more reason to have them; had I known the names of these two, I would have at the very least reported them to the police and considered a lawsuit.

Most responsible bicyclists -- and there are many -- will see this step as a protection for them too, while drivers of other vehicles will see it as a simple act of equity.

A new city council would well serve drivers of all vehicles, including bicyclists, by legislating such protection.

Until then, this driver will never again hear a bicyclist talk about his rights without remembering this incident. ELSIE T. FREEMAN Washington

The doctor's condolences. You have a right to be outraged. All bicycles in the District are required to be registered, according to the city's bicycle coordinator, Tom Pendleton, but there is no requirement that they display any ID number. "No practical way has been found to mount a plate large enough to be seen," Pendleton said.

The D.C. Council, in response to complaints in this column and elsewhere, passed a law requiring that couriers be tested and licensed. That law also requires couriers to wear identification that can be easily seen. However, the District government, with "only" 48,000 or so employees, has not been able to detail anyone to issue the licenses. Maybe the next administration . . . .

Cyclists Get Boost on Hill

Judging from the mail received here, a large number of people either use bicycles to commute to work or advocate better paths and consideration of bicyclists to ease traffic congestion, save fossil fuels and avoid damaging the environment.

Here's a note of interest:

Last month Rep. Peter A. DeFazio (D-Ore.) introduced House Concurrent Resolution 369. The bill details many reasons why bicycling is important. The bill recommends that:

The Department of Transportation should detail how bicycle use will be promoted.

The National Highway Traffic Safety Administration should give bicycle safety a high priority.

State and local governments should give bicycle safety a high priority.

State and local governments should encourage engineers and planners to provide for bicyclists in the design, construction, reconstruction, maintenance, operation and management of the nation's transportation system.

Because this session of Congress is about to end, there is little hope that this bill will be passed. The intent, according to Brad Devries in DeFazio's office, is to build knowledge among members of Congress to help obtain money and policy embodying this sentiment when the Surface Transportation Act comes up for reauthorization next year.

For more information, call Devries at 202-225-6416 or Andy Clarke at the Bicycle Federation of America 202-332-6986.

Dr. Gridlock appears in Metro 2 each Friday to explore what makes it difficult to get around on roads, from misleading signs to parking problems to chronic bottlenecks. 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.