The Institute rates vehicles good, acceptable, marginal, or poor based on performance in high-speed front and side crash tests plus evaluations of seat/head restraints for protection against neck injuries in rear impacts. The first requirement for a vehicle to become a Top Safety Pick is to earn good ratings in all three Institute tests. Another requirement is that winning vehicles must offer electronic stability control. This requirement is based on Institute research indicating that ESC significantly reduces crash risk, especially the risk of fatal single-vehicle crashes, by helping drivers maintain control of their vehicles during emergency maneuvers.