walter reed shuttle to the white house?

my office window downtown looks over 16th street between l and m. every friday morning, police block traffic so a few buses with walter reed logos on the side can get through southbound unimpeded by traffic. now, i'm curious, what are these buses doing? i can't find any information about this with a cursory glance around the web. are injured soldiers being brought down to the white house for press availability?

please tell me if i'm wrong about this, but if injured troops are being paraded in front of the cameras for propaganda purposes, i think that's pretty low. hopefully, these shuttles are for something less sinister.