Dear Dr. Gridlock:

I want to bring to your attention something that happened to me and that perhaps your readers should know:

On a recent night around 9 p.m., I was driving on I-295 when a man started honking his horn and pointing to my front tire.

I rolled down my window and he shouted, "Your wheel is about to fall off."

Although I had not noticed anything particularly different in the way the car was handling, I pulled off the road.

The man got out and showed me that the wheel seemed to be loose. He said he was a mechanic who worked for Goodyear, and that if I took the car into a shop it would cost $600 to fix, but he would fix it on the spot for $500.

I did not know if he was lying or not, but I told him I couldn't pay that amount, that all I had was $50.

He then "fixed the tire" and took the money.

The experience was disturbing, and although I had doubts about this man and what was said and what he had done, I didn't feel I could take a chance of having an accident since I was on the way to Reagan National Airport to pick up my mother.

The man was very friendly and pleasant, but I believe he perpetrated a scam on me.

It might be helpful for your readers to know that such people are on our roads.

Raena Price-Kaufman

College Park

First, I am grateful that all you lost was $50. An inexpensive way to learn a lesson. And it was good of you to share your story with our readers.

I'm afraid you could have lost a lot more than money to this man.

It's generally not a good idea to pull over at the behest of a strange driver, or to agree to have repairs done on your vehicle by a stranger whose office is the street.

I have been approached by men wanting to "repair" dents in my vehicle while I was parked in a lot. I waved them off. Who knows where that would lead, or what kind of job they would do? And there have been reports of drivers deliberately rear-ended by other drivers who then file claims with the victim's insurance company.

What kind of scams have you folks encountered on our roadways?

Overnight Metro Parking

Dear Dr. Gridlock:

Is it possible to park at Metro lots overnight? What would happen if I parked at one while on vacation?

Lucy Whitley

Falls Church

Metro has three stations with parking spaces set aside for overnight use. They are at the Franconia-Springfield, Huntington and Greenbelt stations, according to Metro spokeswoman Lisa Farbstein.

There are 15 to 17 spots available at each station, on a first-come, first served basis, with no limit on the length of stay, she said. Customers exiting these stations would be charged only for parking that day.

Other than those spots in the three stations, "people are not to park their cars in lots for more than 24 hours, or they risk getting a ticket," Farbstein said.

Vive le Traffic Circle!

Dear Dr. Gridlock:

Just returned from two weeks in France and am more convinced than ever that traffic circles are the answer to some of our problems.

On the way home from our airport, we sat in six intersections with no traffic moving through them during green lights. There were plenty of vehicles waiting to cross, however, on red lights.

Bob Bailey

Silver Spring

It makes no sense to have vehicles stopped at a red light when there is no one waiting to cross on green. We have to fix that.

Most traffic lights in this area work on sensors embedded in the pavement to trigger a change, or on fixed times. Seems to me we should get rid of the timed phases, because they can cause motorists to sit for no reason.

Traffic circles eliminate red lights altogether. This seems to me to be a good thing. They also drastically reduce dangerous side-angle collisions.

Maryland has bought into traffic circles in a big way, installing dozens throughout the state. Virginia is slower to embrace the concept: The Virginia Department of Transportation has one on the books -- at the dangerous, congested intersection of Routes 15 and 50 in Loudoun County. It is not scheduled for completion until 2009.

Transportation researcher Diane Mattingly contributed to this column.

You can write to Dr. Gridlock at 1150 15th St. NW, Washington, D.C. 20071. He prefers e-mails at drgridlock@washpost.com or faxes at 703-352-3908. Include your full name, town, county and day and evening telephone numbers. Dr. Gridlock cannot take phone calls.