The snowstorm predicted this weekend by the Capital Weather Gang will be a challenge for anyone trying to get around Washington. But transit users might encounter some unique problems.
Although you'll see many local officials advising people to take transit if they must travel, there's still reason to be cautious. The bus services people use to get to work Friday might encounter some difficulties in getting them home. This could involve slow trips and detours. It's possible -- as we saw in the December storm -- that some buses won't be able to complete their trips. Have a plan for getting home, and leave work early if possible.
What happens on specific bus routes depends on the conditions drivers are encountering and what they are telling their supervisors. The decisions they make about whether to proceed or detour on certain routes will be made quickly. It's very unlikely that Metro's alert systems will be able to keep up with conditions on specific routes.
Metro has a bus service alert on its Web site, and it uses a Twitter feed for service alerts. There is an e-Alert system for problems on the train lines and MetroAccess, but not for problems on specific bus routes.
If conditions deteriorate significantly, as they did in December, Metro could restrict bus service to snow emergency routes.
Bus travelers can try Metro's Next Bus real-time arrival system, available by phone or online. But don't bet your life on the system's accuracy in predicting when a bus will arrive at your stop in a storm.
In some cases, it will be a lot more accurate than the printed bus schedule. But the GPS-based system relies on a computer model of how long it should take buses to get from one stop to the next. A detour, an icy patch in the road, a sudden traffic jam will throw off the prediction.
One aid to navigating with Next Bus: If you're waiting at a stop and getting a Next Bus prediction, look as far down the road as you can see. Is the traffic jammed or moving well? If it's jammed, then it's likely that the Next Bus prediction will be thrown off.
Some precautions apply in any snowstorm: Be careful walking on the brown tiles on station mezzanines and platforms. Even if they are not directly exposed to the outdoors, they can become wet and slippery.
I thought Metro did a good job this week in treating the exposed parts of the outdoor platforms. But in a very big storm, there is only so much that can be done. Metro crews cannot simply push all the snow from the platforms onto the tracks. That would have a bad effect on the trains. Metro must wait until after the train system shuts down at night to bring in specialized railcars that can take away the platform snow.
The big issue will be this: Metrorail operates very close to a normal schedule in snowfall of up to six inches. Once snow reaches a depth of eight inches, snow starts to cover the third rail. Also, snow can interfere with the railcar power system, although Metro takes the precaution of hardening the undercarriages before a storm arrives.
So if the snow on the tracks reaches eight inches, Metro's policy dictates that aboveground operations be shut down. It's difficult to predict when or if that will happen this weekend. You won't be able to tell just by monitoring what the weather people say about accumulations at Reagan National Airport or in downtown Washington. What counts is how much snow is piled up along the tracks.
As you plan your travels, especially if you travel in from suburban stations, be aware that the train line that takes you in might not be able to get you home. In other words, you could be stranded.
This happened to some people during the December blizzard. If the aboveground stations close, you might have few travel options. At that point, the snow will be so deep that it will be difficult if not impossible to find a bus or a cab. Even walking will be hard.