We have one day of spring training today for the D.C. transportation system to get ready for the 2012 baseball season. At 3:05 p.m., the Washington Nationals will begin an exhibition game with the Boston Red Sox at Nationals Park.

Though the regular season opener is more than a week away, and this is going to be a cool afternoon for sitting around in a stadium, according to the Capital Weather Gang, there’s still likely to be extra traffic at midday and during the afternoon rush.

Look for that in the blocks around South Capitol and M streets, on the Southeast-Southwest Freeway and on the 14th Street, Douglass and 11th Street bridges.

For returning fans, the neighborhood will look relatively unchanged from last season. Marc Fisher had a great description of the neighborhood’s past and future in Sunday’s Post.

Note that the river walk is now open along the Anacostia River between Nationals Park and the Navy Yard.

Metro will be on a regular off-peak scheduled at midday, but there are more eight-car trains in service this week because of the Cherry Blossom Festival. Fans tend to spread out their arrival at games, another factor likely to limit crowding on the Green Line and at Navy Yard station, the closest to Nationals Park. (Use the Half Street exit. It’s closer to the stadium and is bigger.)

By the time the game ends, we’ll be into the afternoon rush. That means Metro will be running the usual peak schedule on the Green Line and everywhere else.

Metro does a good job controlling crowding on the Navy Yard platform, and riders on trains heading toward downtown to make transfers to other lines will be going against the rush-hour flow.

But they are likely to encounter extra crowding at the major transfer stations, L’Enfant Plaza (Blue and Orange lines) and Gallery Place (Red Line).

A fan heading for a Red Line destination on the eastern side of the line might be better off skipping the transfer at Gallery Place and instead continuing on the Green Line to Fort Totten and transferring there.

Those transferring to the Blue or Orange lines will probably be better off doing so at L’Enfant Plaza, even if the station looks crowded, rather than continuing north to Gallery Place, switching to the Red Line over to Metro Center and then boarding a Blue or Orange train.

The design of the Red Line platform on the Shady Grove side at Gallery Place doesn’t match up well with the stopping point for the trains.

They go all the way to the end of the platform before stopping, so a six-car train’s last car is farther up the platform than many people expect, especially if they ride only occasionally. So sometimes, when the six-car train arrives, passengers surge up the platform to try to cram into the last car. (This isn’t a problem with eight-car trains, which fill the entire platform.)

And if you do need to transfer at Gallery, remember to move all the way to the end of the platform. People tend to bunch up near the rear of Shady Grove-bound trains due to the station’s design.

Fans leaving the game may find the Half Street entrance to Navy Yard station very crowded. If they don’t want to wait, they could walk east on M Street and cross over to the New Jersey Avenue entrance. That’s likely to be less crowded, and sometimes puts them in a better spot to get a seat — or at least some breathing room — on the train.

Before heading to the game, check your Farecard or SmarTrip card to make sure it’s loaded with enough value for the return trip. You want to avoid waiting on a long line at the Navy Yard fare vending machines.

There are Metrobus stops in the area for Routes 70, P1, P2, V7, V8, and V9. Check the Metrobus timetables on Metro’s Web site.

The D.C. Circulator bus is scheduled to arrive every 10 minutes by the Metro station’s New Jersey Avenue entrance. It connects riders with the Barracks Row neighborhood, Eastern Market Metro station on the Blue and Orange lines and Union Station, on Metro’s Red Line, as well as the MARC and VRE commuter train lines. (The bus no longer stops inside the Union Station garage.)

While sitting in the stands this afternoon may be a bit cool, it should be a beautiful afternoon for walking. Fans could walk down New Jersey Avenue SE from the Capitol Hill area.

Biking is another option. Check the locations of Capital Bikeshare stations.

Drivers will find parking lots to the north and east of the stadium. Street parking for non-residents is either banned or very expensive all the way up to Capitol Hill.

Metro parking, even at the crowded stations at the ends of the lines, tends to ease up in the early afternoon, so it’s likely that fans would find space in them today. This is a weekday, so they’ll have to pay at the exits.