Doubles combinations: Question Doubles combinations: Answers Are less likely to jackknife than singles. Are less likely to roll over than singles. Require a larger reaction time than singles. Explanation Because doubles and triples are more vulnerable than singles to jackknifing and rolling over, drivers should look far ahead of their vehicles so they can react to hazards well in advance and slow down or change lanes gradually. This questions appears in the following tests: Oklahoma Double South Carolina Double