For commuters who rely on both the Blue Line and the Red Line of the MBTA, the journey isn't so smooth.

Daphnee Puryear deals with it nearly every day.

"It's pretty difficult," said Puryear. "Because you're switching lines or getting on and off, sometimes you have to walk a distance. It's really inconvenient."

The Blue and Red lines are the only lines on the T that are not directly connected.

Transit advocates have pushed for years to extend the Blue Line at the Bowdoin stop down the road to the Charles/MGH stop on the Red Line.

"That would be great, because if I have to go to Mass. General [Hospital], I have to ... get off at Bowdoin and walk, and if the weather's bad, then it's terrible," said Bertha Borin.

The MBTA is currently working on its plan for the future, but in a preliminary draft that was recently released, transit advocates say they were surprised to learn there was no mention of a possible Blue Line extension, which they thought would be a given.

They're now circulating a petition to push transportation officials to move in a new direction.

"It seems like such an obvious thing to want to do when you're talking about connecting health care and jobs and the international airport," said Jim Aloisi from Transit Matters. "These are not trivial destinations."

Aloisi is a former Massachusetts state secretary of transportation.

A direct link between the lines would make travel more seamless between Cambridge, Massachusetts General Hospital, Massachusetts Eye and Ear, Logan International Airport, and communities north of Boston.

Right now, if an MBTA passenger in Cambridge wants to get to the airport, for example, he or she has to transfer from the Red Line to another line and then connect to the Blue Line.

"On the opposite side, we want people in East Boston, Revere, other places in the north to be able to have a one-seat transit ride to Mass. General Hospital," said Aloisi. "That's a high frequency destination for people."

About 530 people have signed the petition so far.

The MBTA is expected to unveil its plan for the future later this year.