Create a new City object with the specified number of East-West
and North-South Roads, keeping in mind the space limitations of
the provided GWindow dimensions.
Scan all of the Roads lying perpendicular to the given Car's
path to see if the Car will be at or inside any of those
intersections at the end of its next movement.
Return the TrafficLight object that exists at this
intersection, or null if no light at that intersection can be
found (perhaps because the intersection does not exist).
Total the car after an accident with another Car! Turn the
body red, send it spinning out of control according to the
direction and speed of the other Car, and set totaled to true.