Sport utility vehicles (SUVs) have been criticized for a variety of environmental and safety-related reasons. They generally have poorer fuel efficiency and require more resources to manufacture than smaller vehicles, thus contributing more to climate change and environmental degradation. Their higher center of gravity significantly increases their risk of rollovers. Their larger mass increases their momentum, which results in a larger braking distance and more damage to other road users in collisions. Their higher front-end profile reduces visibility and makes them at least twice as likely to kill pedestrians they hit. Additionally, the psychological sense of security they provide influences drivers to drive less cautiously or rely on their car for their perceived safety, rather than their own driving. Safety Generally, drivers in SUVs are safer than those in small and mid-size cars. In a 2011 IIHS survey of death rates per million registered vehicles per year in the US, by vehicle style, smaller cars fared worse than bigger ones. Four-door minivans have a death rate (per 100,000 registration years rather than mileage) of 82, compared with 46 for very large four-doors. This survey reflects the effects of both vehicle design and driving behaviour. Drivers of SUVs, minivans, and large cars may drive differently from the drivers of small or mid-size cars, and this may affect the survey result. Rollover A high center of gravity makes a vehicle more prone to rollover accidents than lower vehicles, especially if the vehicle leaves the road, or if the driver makes a sharp turn during an emergency maneuver. Figures from the US National Highway Traffic Safety Administration show that most passenger cars have about a 10% chance of rollover if involved in a single-vehicle crash, while SUVs have between 14% and 23% (varying from a low of 14% for the all-wheel-drive (AWD) Ford Edge to a high of 23% for the front-wheel-drive (FWD) Ford Escape). Many modern SUVs are equipped with electronic stability control (ESC) to prevent rollovers on flat surfaces, but 95% of rollovers are "tripped", meaning that the vehicle strikes something low, such as a curb or shallow ditch, causing it to tip over. According to NHTSA data, early SUVs were at a disadvantage in single-vehicle accidents (such as when the driver falls asleep or loses control swerving around a deer), which involve 43% of fatal accidents, with more than double the chance of rolling over. This risk related closely to