ACS (Aerodynamic Control System) allows high speed vehicles to brake safely.
It work so that when the player accelerate, the "drag multiplier" will set into a low value,
giving the vehicle more aerodynamic and a progressive acceleration and top speed. When the player is braking,
the "drag multiplier" will set into an high value, giving the vehicle less aerodynamic and braking earlier than normal,
even on air. It's switching between acceleration and brake keys automatically.
In this update is there a script which applies to all cars and some presets of settings.
A detailed information is in the instructions text.