Emily wrote:

How big is it (I don't check luggage, so I'm very limited on space).

My device is similar to this one at about 5 inches long by 2.5 inches high:

http://tinyurl.com/rra65

I did note that this new model does not appear to offer white noise as one
of its twenty sounds, however, unless they renamed the sound.

And more importantly, will it drown out interstate traffic just outside
the hotel window?

Interstate traffic is tough, depending on how close it is to your window
and whether the roads are wet. I will say that the device would make it
much more tolerable, as the white noise will drown out most of the variable
sounds outside your window. It probably won't do anything with the noise
of trucks as they downshift right outside your window, though.

If it is that bad, you have no choice but to demand of the hotel management
to put you in a room away from the highway if they desire your recurring
business. I had to do that once in a hotel in Buffalo, NY, that was
literally right along the highway in the city.

After tossing and turning all night to the din of trucks and cars hitting
the pavement cracks, I demanded a room that week and every week thereafter
on the "quiet" side of the hotel or else my weekly room revenue would be
given to another hotel.

--
Peter