concern about the IPV weight resulted in a project by the Texas DOT on trailer-mounted attenuators since the trailers and tractors are lighter than regular IPV. The research concluded that heavier vehicles are still preferential for this type of operation and that the Texas DOT should maintain the current 20,000 lbs requirement [88]. While using IPV provides a great safety benefit for workers, the IPV driver remains in harm’s way. Swedish researchers conducted impact tests on three different attenuator-IPV combinations including a TMA on a tractor (Figure 35), a TMA on an articulated front-end loader, and a TMA on a trailer demonstrating the dangers of an impact to the driver [89]. Using a lighter IPV like a tractor can cause severe neck injuries to the driver.
Figure 35: Impact testing of TMA on a tractor [89] Usually, errant vehicle impacts are head-on and cause the IPV to accelerate forward [88]. Initially, the support of the seat and headrest will restrain the driver from flailing rearward which is a generally less dangerous movement than forward movement. When assenting the risk of injury for the IPV driver, ridedown acceleration of the support vehicle is the recommended criteria [90]. It is known that the weight difference between the IPV and the errant vehicles is a key factor in the IPV accelerations [91]. The use of a heavier IPV is indicated to reduce the risk and gravity of injuries for the IPV driver [88]. Nevertheless, even when using attenuators attached to extra-heavy vehicles, serious damages can occur as seen in Figure 36 especially considering that the errant vehicle can be an 80,000 lb tractor-trailer traveling at 65 mph. In addition, there are concerns with the psychological harm that the IPV driver may suffer daily. 55
