Walk to the left, stand to the right? Metro General Manager Paul Wiedefeld said Metro would prefer that you stand.

The head of Washington's Metro system said Wednesday that the custom of standing on the right side of a Metro escalator to clear the way for people to walk on the left damages escalators.

"We do not promote, obviously, the walking on the left. These are very sensitive pieces of equipment," he said as officials unveiled a new escalator at the Bethesda station.

It's best for escalators when riders stand on both sides of the steps, Wiedefeld said.

He seemed resigned to the notion that commuters will continue to follow widespread escalator etiquette.

"We prefer that they stand as they move up the escalator, but also we know what people will do what they want to do," he said.

On the "Metrorail Rules and Manners" page of the transit authority's website, passengers are advised to "Stand to the right facing forward. Walk on the left."

When asked on Thursday about his remarks, Wiedefeld said Metro riders need to stay safe on escalators to avoid accidents.

"My point is, you've got a 10-story moving escalator, and if you fall, it's not going to be good. That's what I was trying to get to. Just look at those escalators. There's no landings. Once you fall, you're going. That's what I was suggesting," he said.

The escalator company Otis, which calls itself the world's largest escalator manufacturer, recommends that riders stand in the center of the steps.

"It has always been our position that one should not walk on escalators," a company spokeswoman said. "Codes and standards vary from jurisdiction to jurisdiction, but our recommendation is for escalator passengers to step on, hold on to the rail and stay alert."

Walking on an escalator should not damage it, the Otis spokeswoman said.

Kone, the company contracted to provided Metro’s newest escalators, also recommends for safety reasons that escalator users stand rather than walk. A company spokesman said most people are accustomed to stepping up and down steps that are each 7 inches high. Escalator steps are typically 8 1/2 inches high, he said.

“The one-and-a-half-inch difference plays tricks on your subconscious mind and creates the trip-and-fall hazard,” the Kone spokesman said.

The director of San Francisco's Bay Area Transit (BART) System received a flood of angry tweets when he made remarks on Twitter earlier this year that were similar to Wiedefeld's, the San Francisco Chronicle reported.

“My Twitter feed has been explosive,” Bevan Dufty told the paper. “It’s like I had a fire hose pointed at me: ‘This is a conspiracy,’ ‘Don’t believe it,’ ‘It’s a lie.’”

Dufty cited a Wall Street Journal article that said transportation chiefs in China found that standing on the right damaged that side of the equipment.

Two British researchers found in a study of the London subway system last year that the overall group of people in a subway station can move through the station faster if everyone stands on the escalators.

"...[A]verage queue lengths would drop by enforcing the standing policy," Shivam Desai and Lukas Dobrovsky found. "This means less time spent at the bottom of the escalator, and more people can flow through the station."

Another escalator company NBC Washington contacted, Schindler, did not immediately respond to an inquiry about how best to ride an escalator.