It's not the question of going over the white line. The white line is 1 feet in width. There is a set of sensors before and after the white line. The sensors before the line must be armed with the car's axle by being right over it or beyond. There is further 1 feet between the sensor and the white line which means that you can be well over the sensor without going beyond the white line. I think it cannot get any simpler than this to understand.