[lunarhighway]

I believe i read somewhere on some cars these fences where to reduce lift induced when, due to cornering, airflow would pass over the hood sideways (i assume situations like drifting when the car does move at high speeds sideways and conventional spoilers become uneffective at the same time). this apparently produced enough lift to cause undesirable handling.

As such these devices, like more race car aero devices, will be primarry to reduce lift and not drag. because no sensible person will ever go sideways on public roads i don't think these things have any value on a roadgoing car. they are interesting however, because they show that the airflow is not always front to back and, even under normal driving conditions, the direction of the airflow to the cars central axis will change often.

i imagine they might actually make a roadgoing car slightly less stable as they add more surface area to the side profile at the front, in side wind conditions you want most of the surface area to be at the back of the car, so that when the wind pushes the car sideways the back will be pushed out more and the front will steer into the wind, compensating the change of direction... a few (mostely experimental) cars like the tatra, and also salt lake racers used dorsal fins at the rear to enlarge the rear surface and make the cars more stable in side wind conditions.