Types of seat belts

Lap: Adjustable strap that goes in excess of the waist, Used often in older cars, now uncommon except in some rear middle seats. Passenger aircraft seats too use lap seat belts.
Sash: changeable strap that goes over the shoulder. Used mainly in the 1960s, but of limited advantage because it is very easy to slip out of in a collision.
Lap and Sash: Amalgamation of the two above (two separate belts). Mostly used in the 1960s and 1970s. Generally outdated by three-point design.
Three-point: Similar to the lap and sash, but one single nonstop length of webbing. Both three-point and lap-and-sash belts assist to spread out the energy of the moving body in a crash over the chest, pelvis, and shoulders. Until the 1980s three-point belts were usually available only in the front seats of cars, the back seats having only lap belts. Evidence of the possible for lap belts to cause separation of the lumbar spine and the sometimes associated paralysis, or "seat belt syndrome", has led to a review of passenger safety regulations in nearly all of the developed world requiring that all seats in a vehicle be equipped with three-point belts. By September 1, 2007, all new cars sold in the US will need a lap and shoulder belt in the center rear.