Many motor vehicles are known to have a tire carrier that mounts the vehicle's spare tire beneath the vehicle, such as beneath the passenger compartment or trunk of a passenger car or beneath the bed of a truck. A spare tire carrier assembly typically includes a housing that is mounted to the vehicle. A sheave or spool is positioned in the housing, and a cable is wound about the spool, with a free end of the cable extending out of the housing and connected to the spare tire, retaining it in position beneath the vehicle until it is needed. To release and secure the tire to the vehicle, a shaft on the tire carrier is rotated from above. With the spare tire carrier assembly located underneath the vehicleof Daniel Yergin, chairman of its IHS CERA division, formerly known as Cambridge Energy Research Associates. Yergin's books include the best-seller The Quest, about the evolution of energy markets since the end of the Cold War, and 1993's The Prize, a Pulitzer Prize-winning history of the oil industry.

The firm's outlook is gloomier than some economists' assumptions earlier. In an interview earlier this month, Moody's Analytics chief capital markets economist John Lonski said U.S. gasoline prices would reach $4.75 a gallon if Iran closed the strait.

The impact would be so large because global oil supplies are so tight, said Burkhard. The world has only between 1.8 million and 2.5 million barrels per day of unused production capacity, down from 6.2 million in 2009. Tight inventories magnify the impact of