for passenger cars which collide with the rear of the trailer. Public awareness of this safeguard was increased in the aftermath of the accident that killed actress Jayne Mansfield on 29 June 1967, when the car she was in hit the rear of a tractor-trailer, causing fatal head trauma. After her death, the NHTSA recommended requiring a rear underride guard, also known as a Mansfield bar, an ICC bar, or a DOT bumper. The bottom rear of the trailer is near head level for an adult seated in a car, and without the underride guard, the only protection for such an adult's head in a rear-end collision would be the car's windshield and A pillars. The front of the car goes under the platform of the trailer rather than making contact via the passenger car bumper, so the car's protective crush zone becomes irrelevant and air bags are ineffective in protecting the passengers. The underride guard provides a rigid area for the car to contact that is lower than the lip of the bonnet/hood, preventing the vehicle from squatting and running under the truck and ensuring that the vehicle's crush zones and engine block absorb the force of the collision. In addition to rear underride guards, truck tractor cabs may be equipped with a Front Underrun Protection System (FUPS) at the front bumper of the truck, if the front end is not low enough for the bumper to provide the adequate protection on its own. The safest tractor-trailers are also equipped with side underride guards, also called Side Underrun Protection System (SUPS). These additional barriers prevent passenger cars from skidding underneath the trailer from the side, such as in an oblique or side collision, or if the trailer jackknifes across the road, and helps protect cyclists, pedestrians and other vulnerable road users. In Europe, side and rear underrun protection are mandated on all lorries and trailers with a gross weight of or more. Several US states and cities have adopted or are in the process of adopting truck side guards, including New York City, Philadelphia, and Washington DC. The NTSB has recommended that the National Highway Traffic Safety Administration (NHTSA) develop standards for side underride protection systems for trucks, and for newly manufactured trucks to be equipped with technology meeting the standards. In addition to safety benefits, these underride guards may improve fuel mileage by reducing air turbulence under the