tefilas haderech

Yes, unless it is from brooklyn to lakewood

Probably. The best Eitzah in any Safek about Tfilas HaDerech is to say it in Shma Koleinu during Shacharis.

Do you say Tefilas Haderech between Washington and Boston, since you have to pass through an uninhabited area, and the area is almost 100% built-up in the middle.

It isn’t built up by a long shot. Look at google maps

dafyomi: Why do you assume that?

If you hold that the barrier surrounding I-95 counts as being a rural (outside the city) area with no habitations, you’ll have an oportunity, but we normally don’t hold that a park that is built by design qualifies (i.e. you don’t say Tefilas ha-Derekh when passing through Central Park), and you could argue that the barrier surrounding the highway to protect the local houses should be treated similarly. If so, it is unclear where exactly the northeast “megalopolis” pauses enough to allow for Tefilas ha-Derekh. For all purposes, the Washington-Boston corridor is a gigantic city. The issue is how you extrapolate from a definition designed for an era where people often walked or went a ox-carts in an area in which cities were well definied and surrounded by farmland. If you look out the window on a train you will be hard put to find the uninhabited farmland that categorizes the space between a city that sets up the need to say Tefilas ha-Derekh.