Examples
Allowed
Allowed since all 3 routes cross at approx the same point on the block.
Not Allowed
NOT allowed since the blue (left) and orange (right) path never intersect or come close to each other on the same grid.
The car has to pass through the same 1x1x1 grid (yellow box in screen below) 3 times. As long as the intended (and fastest) path cross that box 3 times, you are fine.
In this example, driving two times over the blue floor and once on top of the white hall thingy does NOT count as a 3-use.
Flying through does not count as driving on the block.