No matter who one asks, a second rail line downtown is the most important project on DART's agenda, essential to the transit authority's future. It will expand the capacity, and the possibility, of transit infrastructure that is currently strangled by the manufactured bottleneck of four above-ground train lines running on the same set of tracks all the way through downtown.

Whenever there's a problem downtown — like, say, a car plowing into a train — the whole train system gets delayed downtown and trains throughout DART's services area are affected, DART President Gary Thomas said Monday. The slowdowns are a problem, Thomas and his audience, the Dallas City Council's transportation committee, agreed Wednesday. So are overcrowded Red Line trains during rush hour. There was more disagreement, however, over the best alignment for the planned second downtown line.Thomas was clear Monday that DART prefers some variation of an alignment the agency calls "B4," because it would allow for a stop at the convention center, is cheaper because it's an above ground line and, in DART's view, has a better chance of securing the federal grant money needed to build the project. As originally drafted, B4 has some major problems. Building the alignment would require tearing down First Presbyterian Church's parking garage and several recently constructed townhouses near Dallas Farmers Market. To potential keep the buildings intact, DART has developed a workaround that would redirect the tracks from Young Street to Jackson Street after the rail line passes in front of City Hall.

Council Member Adam Medrano, who represents parts of downtown, said he couldn't support any alignment that would threaten property near the farmers market. His colleague, Philip Kingston, was more pointed in his criticism.

"I'm not a big fan of making a 30-year mistake on the back of talking about funding," he said.

Kingston, like much of Dallas' new urbanist crowd, prefers the Commerce Street subway, otherwise known as alignment B7a. The problem with downtown's current rail alignment was that it was built above ground, he said before asking Thomas whether DART could run more trains if downtown stations were underground (they can).

If second line is built as far south as DART suggest, it wouldn't be the effective alternative to DART's current system DART wants, Kingston said. If the current line is shut down, as periodically happens, riders might be unlikely to make the trek from Pacific Avenue all the way south to Young Street, a straight-line distance of about a third of a mile to three-quarters of a mile, depending on where you get off the train.

DART wants to get the ball rolling on the new line now, because it will have an advantage in applying for the federal core capacity grant it wants if it can submit a proposal to the feds by the end of September. Part of putting that proposal together is getting the City Council to sign off on a city-preferred alignment. The transportation committee will vote on a preferred route to recommend to the full council in two weeks.