Our exercise consists of staging two vehicles, a lane apart, on the airport taxiway. I generally drive the so-called rabbit. The student is in the other vehicle, with an instructor riding shotgun. The drill is that I accelerate to about seventy kilometres per hour, then stabilize at that speed. The student maintains station about half a second to one second behind, a common spacing in heavy traffic. Without warning, I perform a full emergency stop, while the student tries to get his or her own vehicle halted in time. They never succeed, despite, as the instructors point out, being as ready to act quickly as they are ever likely to be in everyday driving. In fact, I have had the other vehicle overshoot by thirty metres on occasion.
If you are following too closely behind a modern, well-designed car, and the driver goes to true threshold braking, you will not stop in time. Note the phrasing. It is not that you might have difficulty, or be unlikely to avoid the wreck. You will crash, just as someone who is in a so-called terrain trap will be buried if an avalanche occurs.
These days more and more cars are coming equipped with brake assist, which means even a tentative motorist can achieve maximum emergency slowing. In the past, the fact that most drivers couldn’t execute a proper panic stop gave the tailgater a bit more of a chance. That, increasingly, is no longer the case. Teasing grizzlies might be a better gamble.