How does following distance for doubles compare to single-trailer combinations?

Doubles combinations need longer following distance than single-trailer combinations for two reasons. First, the combination is longer (often 65-75 feet for a typical double versus 55-65 feet for a single), and the 'one second per 10 feet of vehicle length' rule of thumb requires more space. Second, the consequences of having to brake hard or steer suddenly are worse because of rearward amplification and the increased rollover risk. Add at least one extra second of following distance for doubles, and more for triples. The defensive driving philosophy applies more strictly: leave yourself enough margin to avoid panic maneuvers entirely.