Dear Dr. Gridlock:

I am writing to inform you of a recent development regarding the George Washington Parkway, specifically the stretch south of Alexandria. I recently noticed that signs have been placed along the parkway saying “No Bicycles.” I have learned that the superintendent of the parkway issued a “Certificate of Determination” on Aug. 5 stating that bicycles are not allowed on the parkway.

It appears that there was no discussion with members of the bicycle community or motorists regarding this decision. The Washington Area Bicyclist Association has sent a letter to the superintendent requesting a meeting to discuss this matter and challenging the decision.

I am an avid cyclist and have cycled this part of the parkway for over five years. I believe I should have the right to continue to do so. I don’t think that cars should have sole use of the parkway. It is possible to share the road.

— Ken Waigand, Alexandria

The statement signed by Superintendent Dottie P. Marshall “reconfirms and restates” a National Park Service policy dating from 2007 that bars bicycles from the George Washington and Clara Barton parkways for safety reasons. The statement anticipated that additional signs about the ban would be posted.

The Washington Area Bicyclist Association, one of the D.C. region’s leading advocates not only for the interests of cyclists but for traffic safety generally, has responded with a letter to the Park Service saying that this policy is unfair.

In recent years, I’ve heard from cyclists and drivers on this issue, particularly about cycling on the southern portion of the George Washington Parkway. And just last month, we had an exchange of letters about similar tensions between drivers and cyclists over the safety of the crosswalks on the parkway near the Arlington Memorial Bridge. [Dr. Gridlock, Aug. 14]

The Park Service position is that the parkway is heavily traveled by motorists, is narrow and has limited visibility on some curves. Plus, storm drain grates can catch the wheels of bicycles.

Cyclists have safe alternatives, particularly the Mount Vernon Trail along the George Washington Parkway and the C&O Canal towpath trail by the Clara Barton.

The association’s position is that bikes regularly operate safely on curving roads of similar widths and that there is no evidence they can’t do so on the parkways.

Meanwhile, the trails are crowded and speeds are restricted. There’s no trail on the Virginia side north of Roosevelt Island, and the C&O towpath is dirt and gravel.

As with the crosswalk issue, I favor solutions that emphasize safety over convenience.

I’d separate types of travelers in these particular environments, but I think the cyclists have a strong case about the inadequacy of the trails.

Experience tells me that readers have strong views on this, so let me hear them.

Metro advisories needed

Dear Dr. Gridlock:

There has been almost constant repair work done to the Red Line between Grosvenor and Shady Grove during the past few years. Now it seems we have several more years of disruption to look forward to.

Though weekend single-tracking is still being announced, I never see notices for what seems to be unannounced single-tracking during weekday afternoons and evenings. A recent trip from Arena Stage to Twinbrook on a weekday evening took 90 minutes because of unannounced single-tracking.

Also, I’m surprised I haven’t seen any complaints about the new decision to close stations down completely to speed up the repair schedule.

Do they really think anyone with a car will subject themselves to the shuttle option being offered? I hate driving into the city, but where did I put my keys?

— Elaine Joselovitz, Rockville

Metro has started posting announcements about the weekday single-tracking, and transit authority spokesman Dan Stessel said that will continue.

“These midday track outages had previously been reported by [electronic] alerts as they happened, but we’re now in a position to get a bit of advance warning,” he told me in an e-mail.

We’ll post them early in the week on the Dr. Gridlock blog, at dr-gridlock .

Riders are understandably discouraged about the delays and disruptions, which will be with us for years. But I’ve gotten some positive feedback and few complaints about the strategy that sometimes shuts stations and substitutes free shuttle buses on weekends.

Dr. Gridlock also appears Thursday in Local Living. Comments and questions are welcome and may be used in a column, along with the writer’s name and home community. Write Dr. Gridlock at The Washington Post, 1150 15th St. NW, Washington, D.C. 20071, or e-mail .