Winter brings especially slippery floors for Metro, as riders track in sleet, snow and salt. Metro's solution? Mopping.
The transit agency says it mops the floors at stations where slush prevails because its mopping mixture contains a chemical to make the floors less slippery.
"Typically we do not mop station surfaces during rush hour. However, if snow, slush and/or de-icing salt are tracked into the station, the flooring may become slippery. In that case, we will mop the floor with a chemical that neutralizes the salt and makes the walking surface less slippery," Metro spokesman Philip Stewart said in an email.
The practice bewildered riders during last week's mix of rain and snow, who entered stations to find slippery, mopped floors.
"Anyone know what is going on with theslipperyfloors in metro stations? It feels like I'm iceskating on these tiles," wrote rider Matt Seidel on Twitter, using the handle @mseidel.
Some riders said they slipped in the mopped areas.
"I slipped this morning, as I stepped from a freshly mopped floor onto an escalator. Surely there can be a better time to do this?" tweeted rider Andrew Kilby using the handle @KilbyA_.
Rider Chad Magaziner said he almost fell at Metro Center in a spot that lacked "Slippery When Wet" signs.
"Making it wetter. I don't see how that would help," he said, laughing when he heard that Metro used a chemical to make floors less slippery. "I don't think there's much sense behind a lot of things we experience on a daily basis down there."
Metro officials know their tiles are slippery and have a plan to replace the hexagonal tiles with a sturdier, concrete pavement. But they've had that plan since 2009, and so far only six outlying Red Line stations have new surfaces -- Shady Grove, Rockville, White Flint, Twinbrook, Silver Spring and Takoma.
"Everybody knows the hexagonal tiles are not the right tiles," said Metro board member Bill Euille, who slipped on a wet Metro platform in 2011 and tore a tendon in his knee. "Efforts are being made to correct them and replace them when possible."
New stations on the Silver Line will have the new surfaces, and floors will be replaced when finances and timing make it possible, Euille said.
"It wasn't a plan where they were just going to go out immediately and do whatever x number of stations we had, because it's not economically or financially feasible to do all that," he said.
But Metro doesn't have to worry about getting sued over its slippery floors -- a Maryland court ruled last year that the transit agency was immune from slip-and-fall lawsuits because it was a government agency following a policy, not making a discretionary mistake.