Governor Cuomo came to Manhattan this morning for a press conference marking the start of construction at Moynihan Train Hall, the forthcoming Penn Station expansion into the old Farley Post Office on Eighth Avenue.

The $1.3 billion project will transform the old post office into a “state-of-the-art” waiting area for Long Island Railroad and Amtrak passengers, increasing concourse square footage by more than 50 percent. Moynihan will also include 700,000 square feet of new commercial and retail space.

“The subway system is the economic circulatory system of the entire city,” the governor said today. But while Moynihan will reduce crowding at Penn and create a more pleasant waiting environment, it doesn’t affect subway service. In fact it makes subway connections more inconvenient for intercity and commuter rail riders. As Second Avenue Sagas’ Ben Kabak noted on Twitter, the new waiting area will be a whole avenue farther away from subway stations on Seventh and Sixth avenues.

Expensive transit edifices with no concurrent service improvements, like the Moynihan Train Hall or the new World Trade Center PATH station, have become all too common in New York City. But there’s a way to improve connections between Moynihan and the subway system: a 34th Street transitway.

During the Bloomberg administration, DOT proposed a full-fledged busway on 34th Street, with transit lanes physically separated from other traffic and a large new pedestrian plaza between Fifth and Sixth avenues. It would have been a new standard for prioritizing surface transit on city streets, but that design died in 2011 thanks to opposition from Midtown property owners.

The conventional bus lanes on 34th Street are prone to all the problems that an exclusive transitway is supposed to avoid. They are constantly obstructed, and as a result crosstown service remains slow and unreliable.

The rationale for a full transitway has only gotten stronger in the years since the city abandoned the idea. More development at Hudson Yards is coming, and buses need better self-enforcing street designs to bypass increasing traffic congestion. Maybe some of those influential Midtown property owners have seen the light.

The construction of a new rail concourse without adequate connections to the subway adds one more powerful reason to make 34th Street a great transit street. Riders won’t think the Moynihan hall is very “state-of-the-art” if they feel separated from the rest of the transit system. A fast, reliable busway on 34th Street can connect them.