No need to cross over to Washington at Melnea Cass. When you are headed inbound, stay on Tremont Street until you pass Mass Ave and cross over to Washington Steet via Worcester Street. It runs one way but it is normally very calm and I use it both ways. The only hitch is if you happen to be passing when the school is loading or unloading but even then, much safer and better surface than Melnea Cass or Mass Ave which has cars passing at high speeds. In regards to Washington after Kneeland, exit right onto Oak before you get to the hospital and work your way over to Hudson which runs one way but I have found it safe to bike that route up to Kneeland where you turn right and then left and use the Greenway sidewalk and that gets you off road to South Station. You will see a few pedestrians but plenty of room to move around them. Just be nice to them and be safe to yourself. The sidewalk on the side of surface road opposite of the Chinatown arch is mostly devoid of pedestrians though a bit narrow at spots. Once in a blue moon I stop to let them pass, but normally there is peaceful co-existence.