Even a 12 mph reduction can greatly reduce the severity of a crash. Every foot per second makes a difference.
One problem with suddenly braking hard to avoid a collision in front is then you get rear ended (happened to me). Sometimes the best approach is to swerve onto the shoulder instead (also happened to me, and I watched the guy behind me plow into the guy in front).
One problem with suddenly braking hard to avoid a collision in front is then you get rear ended (happened to me). Sometimes the best approach is to swerve onto the shoulder instead (also happened to me, and I watched the guy behind me plow into the guy in front).