Mayor Vincent Gray made another streetcar promise the city may not be able to keep.

On NewsTalk With Bruce DePuyt this morning, Gray said the streetcar should begin passenger service by late January, early February “at the latest.” District Department of Transportation officials, however, have taken great pain not to make any promises about when the streetcar will begin running on Benning Road and H Street NE.

“The streetcars will start actually moving around in December,” Gray said. “We’ll have passenger service probably starting in January, not later than early February when we get an additional car.”

DDOT spokesperson Reggie Sanders said in an email, “As passenger and rail safety are our top priority, we will work to meet that goal.”

In early November, DDOT chief engineer Nick Nicholson declined to provide an exact date when passengers service will begin, instead saying they would get it running “as soon as we can.”

At issue is the testing and certification period, which will begin in December. Passenger service can begin 30 days after that is completed, but a completion date is unclear. Sometime in 2014 was the best Nicholson could do.

As NBC4’s Adam Tuss found out today, getting H Street used to the streetcar could be a long process. Today, Tuss took a trip on a a hi-rail vehicle that “simulates streetcar height/width before the real ones hit the tracks.” This is what he found: “It took us about an hour to go 5 blocks on H street in the test vehicle. We were blocked by 5 other vehicles.” Ticketing and towing begins on December 1.