Organizers of the Marine Corps Marathon announced on Wednesday changes to the 26.2-mile race and accompanying 10K, including course alterations and extra time for runners to cross the starting line. The adjustments are due to ongoing repairs of the Washington, D.C., Metro system that could affect travel to the starting line on October 30.

The changes were announced at a press conference in Rosslyn, Virginia, which was broadcast over Facebook Live. 

The Washington Metropolitan Transit Authority has eliminated the early openings that have previously accommodated special events like the marathon. In past years, rail service began at 5 a.m. on marathon weekend. It will not be available until 7 a.m. this year, though the marathon will maintain its planned start time of 7:55 a.m.
Because of the restricted transit options, race organizers are implementing a few measures to help participants. For example, the traditional time cutoff point for the marathon requires runners to get to the 14th Street Bridge, the 20-mile mark of the course, by 1:15 p.m. or be shuttled to the finish area.
That time cutoff remains, but due to course alterations, the 14th Street Bridge is now the 18th mile of the course instead of the 20-mile mark. The new route reduces two miles from the segment on the Rock Creek Parkway and adds mileage to the course in Arlington and Crystal City later in the race.
The starting line will also be open until 8:55 a.m. to give all runners ample opportunity to cross the starting line timing mat.
“All of the changes have been governed by the principle that every participant deserves a fair chance to accomplish the goal of finishing the Marine Corps Marathon within the required 14-minute-per-mile time limit," said Rick Nealis, the Marine Corps Marathon director, in a statement.
Race organizers urged runners to consider alternate means of transportation to the race start. Those include driving to designated parking lots where runners can take a shuttle to the start. 

A How to Break 4 Hours in the Marathon can be found on the race website.

The race expo also has a new location this year, the Gaylord Resort at the National Harbor in Maryland. For runners staying at that hotel, shuttles will run directly to the start.

For athletes who want to rely on the Metro, train service will be increased  between 7 a.m. and 9 a.m. on the yellow line and between 7 a.m. and 4:30 p.m. on the blue line.

To prevent the marathon from running into the 10K, the 10K starting line will move from the National Mall to the Pentagon north parking lot. It will still start at 9:15 a.m. 

According to Running USA, 23,184 CA Notice at Collectionth How to Break 4 Hours in the Marathon.

On race morning in 2015, a Metro railcar hit a deer on the track, delaying runners on their way to the start. Security checkpoints then became overloaded as many thousands of runners tried to enter the race staging area at once, while several metal detectors malfunctioned. Some runners waited as long as an hour to pass through the security and missed the start of the race. 

The press conference can be viewed below: