Benefits and Costs of Four Approaches to Improving Rollover Stability of Cargo Tank Motor Vehicles

Four broad approaches to decreasing the number of cargo tank rollovers were evaluated: driver training, electronic stability aids, improvements in design of the vehicle itself, and highway design. A study of rollover crash statistics confirmed many expectations, but a few of the factors were not as strong as might have been expected. The portion of rollovers that occur on freeways is 15% to 20%. A driver error of one kind or another (e.g., decision or performance error) figures in about three-fourths of cargo tank rollovers. Inattention and distraction account for about 15%. Evasive maneuvers were a factor in 5% to 10% of rollovers. Drivers must be trained to appreciate the diverse causes for rollovers and to anticipate the situations that lead to them. Adherence to viable work and rest schedules is crucial. Electronic stability aids automatically slow the truck when it rounds a curve too fast. They can be remarkably effective in preventing this scenario. However, crash statistics and anecdotal accounts consistently show many other factors that can lead to rollovers. Significant reductions in rollover rates can be achieved with modest changes in vehicle stability. Cargo tank trailers of improved stability are currently available for some cargoes. When mountainous terrain or other factors dictate highway designs that can contribute to rollovers, drivers need to be made aware through signage or dispatch instructions. A comprehensive benefit-cost analysis, conducted from a societal point of view during a 20-year window, projected that the improvements will be cost beneficial.