But the road as seen is never traversed.

It is thought of as being traversed because the intrinsic characters of the later events are in general so similar to those of the instantaneous road that we do not trouble to discriminate.

But suppose a land mine under the road has been exploded before the lorry gets there.

Then it is fairly obvious that the lorry does not traverse what we saw at first.
Suppose the lorry is at rest in space {beta}.

Then the straight line r of space {alpha} is in the direction of {beta} in space {alpha}, and the rect {rho} is the representative in the moment M of the line r of space {alpha}.