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:

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:

I've found that almost always someone will let me in when I'm signaling in heavy traffic.

As for your remark about your occasionally forgetting to use the turn signal, I'd argue that a well-disciplined driver would never do that. Using the turn signal should be second nature, like fastening your seat belt or tying your shoes.

When I see someone next to me signaling, I will always let him in, the only exception being obvious line-cutters. If I can see someone is trying to cut in front of me but isn't signaling, I will actively box that person out, within the limits of safety. Defensive-driving proponents may chide me for that, but I figure I'm just doing my small part.

I don't blame drivers' laziness for the problem. None of the local police departments has any interest in enforcing turn signal rules. Nothing irks me more than seeing a cop turn without signaling.

When I see someone turn without signaling (while yapping on the cell phone), it reminds me why my auto insurance is so high despite my clean driving record.

Greg Parker

Alexandria

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

Dear Dr. Gridlock:

The turn signal has evolved into a visual Pavlovian cue inducing the driver in the next lane to stomp on the gas and close the gap.

That response has developed over decades of ever-increasing road congestion and driver frustration to produce a "you-ain't-getting-in-front-of-me-buster" mentality, which was a shock to me when I moved here from Seattle 13 years ago.

Fortunately, I've learned how to use the "blinker effect" to my advantage. With proper timing, my turn signal induces the person in the next lane to speed up while I decelerate and glide in behind that car. This little maneuver works like a charm!

Steve Alexander

Alexandria

I find that about half the time when I use my turn signals, the driver in the next lane will speed up to prevent the turn. I like your adaptation and will try it.

Get Bikes 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 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 right 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.

Double-Parkers Moved

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 at around 4:45 pm.

Looks like e-mails to the mayor as well as comments to Police 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.

Bus Beats Slug Lines

Dear Dr. Gridlock:

This letter is in response to a question asked by Hal Nesbitt of Dale City on May 20. Mr. Nesbitt needs transportation between Woodbridge and Springfield and asked about slug lines so he can get to job interviews.

There is a great resource right in Mr. Nesbitt's back yard: PRTC. The Potomac and Rappahannock Transportation Commission has a bus route, the Prince William Metro Direct, that loops continuously between eastern Prince William County and the Franconia-Springfield Metro station.

Buses start running at 5:30 a.m., and trips are offered hourly (even more frequently during rush hours) until 11 p.m.

The fare is $2.50 each way. Passengers can purchase 10 tokens for $20. Free regional transfers are available for passengers transferring to other bus lines.

The Prince William Metro Direct includes stops at the Horner Road commuter lot, Potomac Mills mall and the PRTC Transit Center on Potomac Mills Road.

Customers who don't live near the Metro Direct bus route can access it by riding a local OmniLink bus.

By taking the bus, Mr. Nesbitt can start his trip home as soon as his job interview is over rather than waiting until the afternoon slug lines start forming.

For more information, call PRTC at 703-730-6664 or go to www.PRTCtransit.org.

Christine Rodrigo

Public relations specialist

Potomac and Rappahannock Transportation Commission

Thanks for the tip. That is bound to help some people.

Transportation researcher Diane Mattingly contributed to this column.

Dr. Gridlock appears Sunday in the Metro section and Thursday in Fairfax 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.