I recently solicited motorists' pet peeves about other motorists [Dr. Gridlock, Aug. 14]. Not surprisingly, there are plenty of bad habits that drive people bonkers. Here are some:

Dear Dr. Gridlock:

My pet peeve is people who refuse to also turn on their headlights when they have turned on their windshield wipers. It's a simple act, but most helpful.

Gene McClung

Potomac Falls

It's also the law.

Dear Dr. Gridlock:

Here are my pet peeves:

* People who treat the world as their ashtray, flicking cigarettes out their car windows. I once saw someone empty their car's ashtray out their door while they were waiting for a traffic light. It's not only littering, but it could be dangerous if a still-lit butt flies into the window of a car behind you.

* The folks traveling solo in the HOV lanes by virtue of the "blue light" they purchased and affixed to their dashboard. I saw a fellow in a Ford 500 sedan traveling solo in the HOV lanes of Interstate 95 this morning with an aftermarket blue light on his dash. Maybe we should all look into that method, since it's obviously cheaper than buying a new hybrid car.

John Braun

Lake Ridge

A blue light is the exclusive domain of law enforcement. I suppose the aftermarket devices you are seeing could be for undercover police work. Impersonating a law enforcement officer carries a serious penalty.

Dear Dr. Gridlock:

Perhaps your reader who complained about drivers who speed up or slow down to prevent others from entering their lane is, in fact, the real jerk [Dr. Gridlock, Sept. 11].

Your reader may be one of those people who try to speed past everyone else in exit lanes so they can merge (and cut others off) at the last minute, gaining an advantage over the sane, responsible drivers.

Anyone who travels south on Interstate 495 toward Tysons Corner can attest to that kind of behavior.

Drivers speeding along in the three left lanes suddenly attempt to cross two to four lanes to get on the Dulles Toll Road exit ramp before Tysons Corner. Their actions do nothing but cause stop-and-go, bumper-to-bumper tie-ups.

Responsible drivers anticipate which lane they should be in when approaching their exit and do their best to help all traffic move smoothly.

Such responsibility is often in vain because of the jerks who want to gain a 15-second personal advantage but end up delaying everyone by 15 to 20 minutes.

Herb Miller

Vienna

Dear Dr. Gridlock:

Among my pet peeves are:

* Drivers who flick their cigarette ashes or butts out of their window instead of using the ashtray. Convertible drivers are rewarded with ashes or worse flying into their cars.

* Drivers who take nap time at a traffic light, particularly in "turn only" lanes.

* Pokey "left-laners." At first I thought all these people were British, since they head for the left lane as soon as they turn onto a roadway!

* "Swingers" who make a wide swing in the opposite direction when turning.

* Those who apply makeup or write when driving.

David Wase

Arlington

Dear Dr. Gridlock:

My pet peeve is drivers in the left lane who, when a traffic light turns green, stay behind the stop line and fail to move up into the intersection and/or turn until the last moment.

I have even seen some of these folks -- who are always ahead of me, of course -- stay behind the stop line through the complete green light cycle until the light turns red again.

Robert Van Epps

Arlington

Dear Dr. Gridlock:

My pet peeves are:

* Rolling stops. Stop signs and red lights are there for a reason. Living in a community with direct access to Interstate 395, I can't count how many times I have witnessed drivers barely slowing down for the stop signs. That is not only dangerous, it's idiotic.

* Constant speeding, especially on George Washington Memorial Parkway. The parkway is not an interstate. Stay within the speed limit (40 mph for a long stretch in the vicinity of the airport and 50 mph on other parts). I routinely am passed by vehicles driving in excess of 50, even 60 mph.

* Combining driving with other activities such as reading, eating, smoking, talking on a non-hands-free cell phone or watching a TV or video screen.

Robert Johnson

Alexandria

Dear Dr. Gridlock:

Two letter writers mentioned pet peeves that involve backing out of parking spaces [Dr. Gridlock, Sept. 11]. That brought up one of my ongoing puzzlements: Why do drivers pull front first into spaces in parking lots so they then have to back out blindly and awkwardly into traffic in the lot?

Unless there is a notice requiring otherwise (front-end-in only, to preserve shrubbery, for instance), I have always backed into a chosen spot. That means backing into a dedicated, defined space without traffic or pedestrians.

When leaving the space, there is no craning to see over your shoulder, no nearly blind attempt to check for pedestrians or vehicles (especially if an SUV has parked beside you, effectively cutting off almost all side visibility) and no jockeying around one or more vehicles cruising to take over your space.

It seems like a no-brainer to me. It's easy in, easy out.

Nancy Ruth Davis

Arlington

Dear Dr. Gridlock:

You asked for annoying driving habits:

* Failure to signal, particularly when making an abnormal turn (for example, turning right from the center lane), or when changing lanes at higher speeds. Signaling helps other drivers know what you are doing and therefore reduces your chances of having an accident.

* Talking on cell phones while driving in traffic. Illegal or not, it happens all the time, with costs to both attention and control.

* Aggressive driving and speeding on Interstate 395 (Shirley Highway). It gets worse every day with trucks, vans and cars swerving in and out of traffic. State police and other law enforcement officers apparently pay little attention. No wonder there are so many accidents on that highway.

* Speeding on Rock Creek Parkway by the Kennedy Center. If I drive there on cruise control at 30 mph (in a 25 mph zone), I am passed by everybody else, including D.C. police officers. Some drivers yell at me or make obscene gestures. Why is the speed limit 25 mph if nobody observes it and nobody enforces it?

Allan Cameron

Washington

Transportation researcher Diane Mattingly contributed to this column.

Dr. Gridlock appears Thursdays in Extra and Sundays in the Metro section. You can write to Dr. Gridlock at 1150 15th St. NW, Washington, D.C. 20071. He prefers to receive e-mail, at drgridlock@washpost.com, or faxes, at 703-352-3908. Include your full name, town, county and day and evening telephone numbers.