Suppose you go to Dallas and you want to drive the same route as Kennedy's motorcade (minus the part where you get shot, of course.) You won't be able to do it.
Because the motorcade headed west on Main St., turned right (north) onto Houston St., then left onto Elm St., and then Kennedy got shot.
But that right turn onto Houston is currently illegal, as Houston is a one-way street; southbound only.
So, either Kennedy's motorcade got special permission to drive the wrong way on Houston, or it used to be a two-way street back then.