we automobile drivers know that we are supposed to stop (+ yield) to pedestrians in cross walks and remain stopped until they have completed crossing.
however, i believe it is also required of the commencing pedestrian to wait until it is safe: in other words to not just keep walking without stopping to look and see if it is safe to cross.
today a single person just about jumped into the street in front of me, had to jam on the brakes and was stuck in the middle of the intersection, blocking a side street (near Martha's Restaurant, across from Rite Aid).
my personal practice when crossing the street is to look around myself all the time (360 degrees) as I've almost been run over by huge trucks, etc. !!
I see people crossing and they don't seem to look at the vehicles coming at them at all.