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Article: The History of Seat Belt Development

Compartmentalization | State Laws and Requirements | Web Resources


Compartmentalization

What does compartmentalization mean? The term is at the heart of the Great Seat Belt Debate. It was coined during the 1967 and 1972 Series 1 and Series 2 “School Bus Passenger Protection” collision tests conducted at the University of California at Los Angeles. Although not an element of compartmentalization, the UCLA researchers concluded that after high back seats, next in importance to school bus passenger collision safety is the “use of a three-point belt, a lap belt or other form of effective restraint.”

Other UCLA conclusions included:

  • High back seats of 28 inches or more greatly contribute to the compartmentalization of passengers thereby reducing the chances of injuries sustained by passengers being hurled against one another, regardless of their size. Seatback height for school buses should not be less than 28 inches.”
  • Lap belts should not be used with low seat back seats as this would lead to head and chest injuries caused by belted passengers rotating forward and striking the upright backrest ahead.
  • School bus seats should not be provided with rigid protruding structures such as handgrips, handrails or similar injury producing fixtures.
  • Lap belts would provide substantial additional protection if used in combination with high-back seats equipped with additional efficient padding on the rear panel of the backrest ahead.
  • Standees should not be permitted.
  • Seat belts are not recommended for school buses equipped with seats with hard surfaces, a metal bar along the back side of the top of the frame ahead, weak seat frames, or low-back 24 inch seats.

Compartmentalization became the heart of the federal government’s policy of school bus safety. The concept of compartmentalization envisions children riding in a cocoon or compartment surrounded by an energy-absorbing, passive occupant protection system. Some industry experts use the metaphor “egg carton” as in cushioning the eggs inside, to describe compartmentalization.

This is why standees on school buses should never be permitted.

However, the National Transportation Safety Board (NTSB) found that compartmentalization is “incomplete” and “does not protect passengers during lateral impacts with vehicles of large mass, in rollovers and from ejection.” According to NTSB, an occupant crash protection system should be developed that would protect passengers in most accident scenarios.

In response, NHTSA updated FMVSS 207, 208, 210 and 222 to enhance compartmentalization with mandatory requirements for equipping all small Type A school buses manufactured as of September 2011 with 3-point lap/shoulder seat belts. Partly due to compartmentalization and the higher cost of larger school buses equipped with these 3-point seat belts, NHTSA only published voluntary standards for equipping school buses that weigh more than 10,000 pounds with the occupant securement systems.

In addition to padding, today’s seats also must have a steel inner structure that bends forward to help absorb energy when a child is thrown against it, especially those students seated behind who may not be wearing their seat belt. Also, of course, the seat is required to be anchored to the floor strongly enough that it will not pull loose during this bending action, or during collisions. Federal regulation requires each passenger seat to be anchored to the school bus floor and withstand 15,000 lbs. pulling force per seat. The floor itself must be strong enough that it will not be bent or torn by the pulling action of the seat anchors. The NHTSA final rule in 2008 also required quasi-static testing of these seats to ensure that belted as well as unbelted passengers remain protected, or compartmentalized, in the event of a crash.

Seat manufacturers CE White, IMMI/Safeguard and Takata/M2K have also solved the potential of losing passenger capacity on school buses with seat belts by creating seats flexible enough to fit two larger students, such as high schoolers, or three smaller elementary or some middle schoolers per seat.

Seat backs in school buses are also now made higher, wider and thicker than before. After the most recent final rule, seat backs will be required to be at least 24-inches high. All metal surfaces are covered with energy-absorbing padding. This structure must pass rigid test requirements for absorbing energy, such as would be required if a child’s body were thrown against the padded back. The equivalent of a seat back, called a barrier, is placed in front of the first seat at the front of the bus.

Finally, seat backs cannot be farther apart than a distance that is deemed safe. Clearly, if the seats are too far apart, the child could be thrown too far before being cushioned and/or could be thrown outside the compartment altogether. Following further research by the federal government, 24 inches spacing was established as the optimal distance between school bus seats.

“In compartmentalization, the crash forces are absorbed by the vehicle structure which is designed to protect the occupant,” said Charles Hott. NHTSA’s school bus specifications engineer. “In an occupant restraint system in general passenger vehicles, the crash forces are absorbed by the body of the occupant.”

Source: School Bus Passenger Protection; Institute of Transportation and Traffic Engineering, University of California at Los Angeles, by Severy, Derwyn M.; Brink, Harrison M. and Baird, Jack D. (Los Angeles, CA 1967).


State Laws and Requirements

Of the eight states to pass school-bus, seat-belt laws, only Louisiana has been unable to fully implement the requirement to install belts in new buses due to insufficient funding.

The laws in the Pelican State requires supplemental funding be made available by the state legislatures in order to enforce two-point, lap seat belts. Texas was in the same predicament until June 2017, when the state legislature passed and Gov. Greg Abbott approved a new three-point, lap-shoulder belt to replace the old one that requires all school district purchases of new school buses to included the three-point occupant restraints, unless the local school board votes in a public meeting to defer the requirement due to lack of funds. The previous law passed in 2007 made implementation reliant upon funds being appropriated by the legislature.

Louisiana passed its law in 1999, the same year as Florida, which began requiring two-point belts on buses in 2001 but doesn’t make funding available to school districts. Charlie Hood, the retired director of school transportation at the state Department of Education and currently the executive director of the National Association of State Directors of Pupil Transportation Services (NASDPTS), said funding has never been an issue, as the cost of the restraint systems are less than 2 percent of the overall purchase cost of a new school bus.

“Districts have absorbed that upcharge over the years,” he added.

Hood said that, as of July 3, 2013, about 12,000 of the state’s 15,000 school buses in daily service are equipped with the lap seat belts.

New Jersey updated its existing law in August 2018 to require lap-shoulder belts from the previous requirement of lap belts.

Meanwhile, of the eight states with school-bus, seat-belt laws, California, Florida, New Jersey and Texas require students to use the restraints. California student riders also be taught how to use the three-point restraints “in an age-appropriate manner.” New York allows individual school boards to decide if they will provide lap or lap-shoulder belts on buses but does not mandate students to use them.

Nevada passed its three-point law in June 2017, and Diana Hollander, state director of transportation at the Nevada Department of Education, said requirements that students use the restraints will be written into regulation before the mandated goes into effect for the 2019-2020 school year.

California and Florida law stipulate that transportation providers first allocate lap-shoulder belts on elementary-school routes. Both state laws and the one in New Jersey also protect any rider, school district or organization operating a school bus from being ticketed for not wearing seat belts.

Texas school districts must require students to wear their three-point seat belts on buses equipped with them, and they may develop a disciplinary policy to enforce seat belt usage. Texas law also requires student training on the lap-shoulder systems.

Nevada will begin requiring all new school buses in operation by July 1, 2019 be equipped with lap-shoulder seat belts. Arkansas also has a law on lap-shoulder seat belts but first requires local voters to approve property tax increases to pay for them.

Individually, local school districts in other states may voluntarily install seat belts. The National Congress on School Transportation in 2005 passed a resolution that urged the National Highway Transportation Safety Administration to change the federal regulations to only allow lap-shoulder seat belts in school buses 10,000 pounds GVWR and less. NHTSA’s revised FMVSS 222 published in 2010 requires these three-point retraint systems in small school buses while leaving to school districts and states the decision on requiring three-point belts on school buses over the 10,000-pound GVWR threshold.


Web Resources

Presented below are links to Web pages devoted to seat belts in motor vehicle transportation and in school buses.

Final Rules:

  • School Bus Passenger Seating and Crash Protection: Seating Systems, Occupant Crash Protection, Seat Belt Assembly Anchorages 
    Final rule effective Oct. 21, 2011 that upgrades the school bus passenger crash requirements of FMVSS 222

    • Requires new school buses of 4,536 kilograms (10,000 pounds) or less gross vehicle weight rating (GVWR) (“small school buses”) to have lap/shoulder belts in lieu of the lap belts currently required.
    • Sets performance standards for seat belts voluntarily installed on school buses with a GVWR greater than 4,536 kilograms (10,000 pounds) (“large school buses”).
    • Raises the height of seat backs from 508 mm (20 inches) to 6102 mm (24 inches) on all new school buses and requiring a self-latching mechanism on seatbottom cushions that are designed to flip up or be removable without tools.
    • Each State or local jurisdiction may decide whether to install seat belts on these large school buses.

Web Sites:

  • Alabama School Bus Seat Belt Pilot Program: A three-year study to assess the impact of lap/shoulder restraint systems for passenger safety. The program is a result of a study group formed by Alabama Gov. Bob Riley in November 2007 following a fatal school bus crash in Huntsville. The final report was released in the fall of 2010. Study authors admitted that pilot tests at school districts failed to incorporate data from new flexible-seat technology that allows for either two or three students to be bucked up per seat, depending on the student’s age and size (two per seat for large middle school students or high school students; three per seat for elementary school and most middle school students).
  • National Education Association: Seat Belts, School Buses & Safety
  • Safeguard4kids.com: A public awareness website by IMMI describing the benefits of occupant secure ment systems on school buses.

  • School Bus Safety: The Seat Belt Issue
    A review of the issue by the New Brunswick Department of Education, January 2002 [PDF file]

  • IMMI of Westfield, Ind., offers the SafeGuard 3-point lap/shoulder belt securement system. The company’s Web site describes IMMI’s four year research project, including half a dozen full scale dynamic bus crash tests and more than 70 sled tests, to develop a lap and shoulder belt occupant protection system for school buses.

  • HSM’s C.E. White line features the Student Safety Seat System, a 3-point lap/shoulder belt system.

  • Syntec Seating Solutions is another school bus seat manufacturer that offers a 3-point lap/shoulder belt solution for school districts that need to fit either two or three students per seat depending on their age and size.

  • Users interested in learning the arguments in favor of seat belts on large school buses should visit National Coalition for Seat Belts on School Buses. This site offers extensive documentation about the pro seatbelt position.

  • The Network of Employers for Traffic Safety offers guidance about increasing seat belt usage among employees.

Position Papers:

Advisory Letters:

  • Texas SB 693
    Read a letter from Sen. Sylvia Garcia to all state school district superintendents, school boards, transportation departments and state agencies assisting in the implementation of the law that goes into effect for model-year 2018 school buses that requires them to be equipped with three-point, lap-shoulder seat belts.