Dear Dr. Gridlock:

Is it legal in the District, Maryland and Virginia to make a left turn on red from a one-way street onto another one-way street?

Lutz Halfmann

Bethesda

Not in the District, but it is okay to do so in the suburbs after stopping, as long as there is no sign prohibiting the turn.

24-Hour HOV Lanes

Dear Dr. Gridlock:

Last night at about 9:30 p.m., I was returning to Virginia from Annapolis on Route 50. I noticed that the HOV-2 lanes on Route 50 in Maryland are in effect around the clock.

What that meant was that all the car traffic was squeezed into the same lanes as trucks while the HOV lane was empty.

I wonder if you can ask the Maryland Department of Transportation what public good is created by restricting the HOV lanes after rush hours?

Bruce Baker

Falls Church

Maryland officials give the following logic: The Route 50 HOV lanes were converted from a left shoulder, and they want to avoid confusion by restricting the new left lane to just one use. They also want to avoid the shifting-shoulder-lane confusion that they say led to several fatal crashes on the HOV facility on Interstate 66 in Virginia.

This makes little sense to me. The new Route 50 HOV lanes still have a four-foot- wide left shoulder; it's difficult to believe that a motorist would mistake a lane of traffic for more shoulder. Further, the I-66 facility has proved efficient and safe. I can't recall a fatal accident that occurred because of confusion over HOV lane shifts. I'm checking this further.

Special Plate for Hybrids

Dear Dr. Gridlock:

I know solo drivers of hybrid vehicles are allowed on Virginia's HOV lanes, but it is my understanding that such vehicles need Clean Fuel or "CF" license plates in order to be exempt from the HOV minimum-passenger restrictions.

I have noticed more hybrids using the HOV lanes without "CF" plates. Do "CF" license plates cost more?

Rich Roscoe

Prince William County

To be exempt from HOV restrictions, the owner of a hybrid vehicle (gasoline plus electricity or other alternative fuel source) needs to get "clean special fuel plates," which have a string of numbers followed by a "CF," according to Pam Goheen, spokeswoman for the Virginia Department of Motor Vehicles.

The special plate costs $10 a year extra and has the words "Clean Special Fuel," in green, at the bottom of the plate.

Hybrid vehicle drivers without the CF plates are not allowed to use the HOV lanes, Goheen said. Owners who don't want to use HOV lanes can obtain regular license plates.

Maryland, by the way, does not allow an exemption for solo drivers of hybrid vehicles to use its HOV lanes.

In Search of Full Service

Dear Dr. Gridlock:

Much has been made of keeping tires inflated properly, which is good for the tires and for optimum gas mileage. However, this presents a problem for some older people.

They may have physical problems that make it difficult to crouch down.

There used to be "full service" options at gas stations, but they seem to have disappeared.

Perhaps your readers have some suggestions.

Leonard Hudler

Silver Spring

According to industry officials, only about 5 percent of area gas stations still offer full service. That has been the case since station owners figured out that customers would pump their own gas, clean their own windshields and check tire and oil pressure while the attendant focuses on selling junk food.

This can create a problem for the less-than-able-bodied. Some pumps have a button to summon an attendant; some stations will provide full service -- even at self-service pumps -- for a disabled person if more than one attendant is on duty.

I suspect that if you ask at your regular station, the manager will provide help. Best to call ahead. Meanwhile, do any of you know of any full-service gas stations in the Silver Spring area?

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.