I want to catch up with your responses to a May 2 column in which I asked why drivers don't use turn signals. Here are some of your thoughts:

Dear Dr. Gridlock:

From countless observations over decades (not just of failure to use turn signals when turning and changing lanes, but also of drivers using their turn signals after entering turning lanes), I believe many drivers fail to understand the basic philosophy of what turn signals are for. They're not to ask for permission or help; they're to inform other drivers of your plans so they can react accordingly.

Failure to properly use signals creates surprises that lead to accidents and road rage.

Some people won't use turn signals because other drivers will speed up to cut them off.

In reality, I think that if a driver uses turn signals properly (to notify other motorists of their intentions), they will discover, as I have, that having a driver speed up to cut you off is actually very rare. When turn signals become second nature you realize that, by far, most of the drivers react properly.

Once you understand that your turn signals are really there for the other guy, you start to appreciate how they help everyone. The bottom line is: Use them for all turns, all lane changes, all merges.

Just use common sense and common courtesy when you drive. It benefits everyone.

Frank Detaranto

Sterling

Dear Dr. Gridlock:

I think the main reason people don't use them is because drivers will speed up and close the gap when they see another driver signaling. I use my turn signals, and that occurs more often than not.

Because of all the daily traffic delays, drivers in this area just don't want to allow another vehicle to get between them and their destination. If you do not signal, you have a better chance of making that lane change.

I don't condone that, but it is what I observe.

Michael Tubbs

Springfield

Dear Dr. Gridlock:

Failure to signal, especially when changing lanes, may not be just another me-first cultural manifestation. It's a practical impossibility to simultaneously signal, steer and yak into the cell phone!

It happens so commonly in recent years. Why don't police ticket?

John Bauer

Reston

Dear Dr. Gridlock:

I drive on the Beltway toward Tysons every morning, and I've seen this a million times: A driver signals to change lanes, and the driver in the other lane speeds up to prevent it.

It infuriates me every time I see it. If I see someone signal, I make it a point to give him room to merge.

Debra Cook

Burke

Dear Dr. Gridlock:

My one-word answer: stupidity!

Mike Motsko

Springfield

Bikes Should Stay Off Parkway

Dear Dr. Gridlock:

On Rock Creek Parkway this morning, southbound traffic suddenly slowed to a crawl between the Connecticut Avenue and P Street exits. The rare rush-hour backup on Rock Creek is usually attributable to a broken-down car that can't get off the road, but today's slowdown was because of a cyclist who was on the parkway rather than on the bike path.

I understand the need to share most roads with cyclists, but it seems absolutely ridiculous (not to mention rude and a little insane) for a cyclist to use Rock Creek Parkway -- a relatively high-speed, curvy road -- when a safe path is available next to it.

I'm curious about the law here, as well as your take on this from a safety and driving ethics perspective.

Amy Levin

Washington

Bicyclists are entitled to use a lane of traffic, as are operators of motor vehicles. However, the situation you describe sounds dangerous for the bicyclist. The driver of a motor vehicle coming around a curve may not see the bicyclist in time to stop.

Of course, motorists should be more careful, and should share the road, but that will be of little consequence to a flattened bicyclist.

Targeting Double-Parkers

Dear Dr. Gridlock:

The bottleneck on 18th Street NW between M Street and Connecticut Avenue, caused by double-parked cars and trucks on 18th Street, has created havoc daily for commuters. Well -- for the time being, anyway -- the police have taken notice and have been present each day this week as I have passed by that block around 4:45 pm.

Looks as though e-mails to the mayor as well as comments to Chief Charles Ramsey during his online discussions at washingtonpost.com regarding this problem have paid off! Let's hope it lasts!

Thanks to both of them for reacting and to you for your terrific column.

Bob Henkel

Washington

I do hope police are turning their attention toward chronic downtown bottlenecks caused by illegal parking. Eighteenth, 19th and 23rd streets, and H and I streets -- all in the downtown business area -- are places where illegal parkers take away a lane of traffic, causing significant backups.

Transportation researcher Diane Mattingly contributed to this column.

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