There is a standard vehicle acceleration number for most types of cars.  The number tells you that your car has been tested; and that the numbers you are given show how the car performs when it accelerates to its highest speeds.  This is supposed to help the driver determine how fast the car will go when you are driving on the highway, and make the decision to pass another vehicle.   You are supposed to make a more informed decision about passing other cars, if you know how fast your car will travel, when you accelerate and pull out into another lane to pass a car or truck.  Of course, there are other factors that must be considered when passing other vehicles such as:  are you driving into the wind, is there enough car length in the on-coming traffic lane, to be able to safely enter the on-coming lane for 30 seconds or more, and does the road surface seem to be impeding your travel speed.  I don’t think that anyone, or any set of numbers can guarantee a driving decision will always have a certain result.  There are too many variables in that situation, that cannot be controlled.  However, I do think that having this information must be valuable, because they have gone to a great deal of trouble to research and confirm this testing mechanism.  They have even given the result a set of numeric values. You do need to know how many car lengths it will take for your car to stop safely, when you firmly press the brakes.  It's better to know this information BEFORE you need it.