Noun
shoulder belt (plural shoulder belts)
(chiefly automotive) A seat belt worn over one shoulder and diagonally across the upper body (following the lower margin of the ribcage as it descends), providing restraint for the upper torso (often coupled with a lap belt which restrains the pelvic area and prevents submarining).
Since September 1, 2007, all new cars sold in the U.S. require a lap and shoulder belt in the center rear seat. citation Besides regulatory changes, "seat belt syndrome" has led to tremendous liability for vehicle manufacturers. Source: Internet
Motorists who would normally wear seat belts must still fasten the manual lap belt, thus rendering redundant the automation of the shoulder belt. Source: Internet
The shoulder belt is fixed to the aft upper corner of the vehicle door, and is not motorized. Source: Internet
Those who do not fasten the lap belt wind up inadequately protected by only the shoulder belt; in a crash without a lap belt such a vehicle occupant is likely to "submarine" (be thrown forward under the shoulder belt) and be seriously injured. Source: Internet
Vehicle owners tend to disconnect the motorized or door-affixed shoulder belt to alleviate the nuisance of entering and exiting the vehicle, leaving only a lap belt for crash protection. Source: Internet