Victoria?s road crash database does not directly identify truck underrun crashes. A total of 3,488 potential underrun crashes were selected on the basis of DCA codes for the period 1996-2000 inclusive. The three most common types of crashes involved rigid trucks ? a rigid truck hitting the rear of a lighter vehicle, followed by a lighter vehicle striking the side of a rigid truck, and then a rigid truck running into the side of a lighter vehicle. The fourth, fifth and sixth most common types of crashes involved articulated trucks: an articulated truck hitting the rear of a light vehicle, followed by an articulated truck running into the side of a lighter vehicle, and then a lighter vehicle striking the side of an articulated truck. Fatalities were most likely to occur in crashes involving the front of a truck.
A number of assumptions underpinned the calculation of benefit:cost ratios (BCRs), including the actual occurrence of underruns and the effectiveness of underrun protection. For all of the underrun protection scenarios examined, the BCRs were higher for articulated than rigid trucks. The package of front, side and rear underrun had a BCR of greater than 1 for both articulated trucks and rigid trucks, regardless of whether the cost was $500 or $1,000 and whether a 15- or 25- year lifetime is assumed. The BCR also exceeded 1 for each type of underrun protection ? front (at a cost of either $100 or $200), side or rear ? for both articulated trucks and rigid trucks; again regardless of the lifetime.