Competitors run near the Capitol during the 2009 Marine Corps Marathon. (Reuters)

Metrorail’s weekend schedule is usually pretty complicated, but the Marine Corps Marathon will add an extra twist this Sunday. For participants and spectators, Metro remains the best way to get around, but make sure you know the potential for delays.

The rail maintenance program will disrupt service on several lines from 10 p.m. Friday through the midnight closing on Sunday. The maintenance disruption on the Blue Line will be limited to Saturday, because it serves Pentagon, a key station for the Sunday marathon’s start, and Arlington Cemetery, which is nearer the finish line. On Sunday, Metrorail will begin service at 5 a.m., two hours early, to help with the marathon crowds.

Here’s the plan for each disrupted line.

Red Line: Trains will share a track between Twinbrook and Grosvenor and between Forest Glen and Takoma. Trains will operate about every 24 minutes between the ends of the line. But from 9 a.m. to 9 p.m. Saturday and Sunday, Metro will put extra trains in service in the middle of the line, between Grosvenor and Fort Totten. In that zone, trains should reach the platforms about every 10 to 12 minutes. If you travel through the work zones, add about 15 minutes to your normal travel time.

Orange Line: Trains will share a track between Stadium-Armory and Cheverly. They will operate about every 20 minutes. Add about 10 minutes to get through the work zone.

Blue Line: On Saturday, trains will share a track between Franconia-Springfield and Van Dorn Street. They will operate about 20 minutes apart.  Add about 10 minutes to get through the work zone.

Green Line: Trains will share a track between Greenbelt and College Park. Every other train will terminate at College Park, rather than Greenbelt. Between College Park and Branch Avenue, the trains will operate on a normal weekend schedule. But riders traveling through the work zone should add about 10 minutes to normal travel time.

I notice that the marathon’s Web site refers to another work zone where stations will be closed. This is no longer part of Metro’s plan. The only Green Line disruption will be the single tracking between Greenbelt and College Park.

Marathon advice

I’ll have a separate posting for traffic and parking. This is advice for the participants and spectators who will be using Metro.

To reach the start line on Sunday morning, use Pentagon station on the Blue and Yellow lines. Metro will open at 5 a.m., but  the Arlington Cemetery station won’t open till  8:30 a.m. The runners begin at 7:55 a.m., and the marathon sponsors advise getting to the start area two hours early, to get through security.

The Arlington Cemetery station is an easy walk to and from the finish area. But make sure you have enough value on your plastic SmarTrip card or paper Farecard to cover your round trip. The lines at the station’s fare vending machines will be very long.

You also will notice that many out of towners have no idea how to feed their crumpled, soggy paper cards into the fare gates after the event. So be patient. The lines to get through the fare gates are likely to be long.

Smithsonian station on the Blue and Orange lines is closest to the start point for the MCM10K. But the station tends to get very crowded for big events on the National Mall.

Metro will operate extra Blue Line trains between Franconia-Springfield and Stadium-Armory from 5 to 8:15 a.m., and from 11:30 a.m. to 4:30 p.m.

Metrobus:  The Pentagon bus terminal will be closed from 4 a.m. to about 4 p.m. All Metrobus routes that normally use the station will move to Pentagon City station. The Rosslyn bus terminal also will close at 4 a.m. and will reopen about 6 p.m. Its bus stops will move over to Oak Street.