[Jim Sims]

If one can't stop in time to avoid a car braking in front of you, one or more of the following must apply: the driver of the "following" car is not paying attention or has diminished reaction times due to other factors (age, fatigue, medications, etc.), the "following" car's braking is inferior to the leading car due to mechanical and/or traction issues, the "following" car's driver has poor braking technique, or insufficient following distance was maintained. There is no other explanation unless the leading car went into reverse somehow.

If you insist on driving under the assumption that all the drivers on the road are competent and alert you will bend metal again sooner than you wish. Drive defensively, especially in a 911 - SUV and truck drivers often don't even see you!