Search Interpretations

Interpretation ID: perea

Gilbert A. Perea, State Transportation Director
New Mexico Department of Education
School Transportation Unit
Education Building
300 Don Gaspar
Santa Fe, NM 87501-2786

Dear Mr. Perea:

This responds to your letter asking about the modification of your large school buses (school buses with a gross vehicle weight rating (GVWR) of over 10,000 pounds) by the installation of a new seating system that has an integral lap and shoulder belt system. I regret the delay in responding.

You explain that an equipment manufacturer, Busbelts Development Corporation (BDC), has been promoting its seating systems for school buses in New Mexico. You enclose photographs of the BDC product and copies of material provided by BDC. The seating systems appear to be standard school bus bench seats that have been modified to incorporate an integrated lap and shoulder belt system. The shoulder belt portion of the system attaches to the top of the school bus seat back. You state that Mr. Gary H. Murphy of BDC has informed you that "all of the required tests have been completed to conform to applicable [FMVSSs] in a National Highway Traffic Safety Administration certified and approved testing Lab." (1) Further, a BDC brochure states that its system "enhances and complies with compartmentalization . . . ."

In a telephone conversation with Dorothy Nakama of my staff, you asked that we respond to four questions. Each question concerns the safety of the BDC system and whether a school bus that has had its original seats replaced with the BDC seating systems would continue to meet Federal Motor Vehicle Safety Standard No. 222, School Bus Passenger Seating and Crash Protection. Our answers are provided below. In addressing those questions, it might be helpful to have some background information concerning seat belts on school buses.

In response to the Motor Vehicle and Schoolbus Safety Amendments of 1974, we issued a number of safety standards under our Vehicle Safety Act (49 U.S.C. 30101 et seq.) to improve protection to school bus passengers during crashes. One of these standards was Standard No. 222, which provides for passenger crash protection through a concept called "compartmentalization." Prior to issuance of Standard No. 222, we found that the school bus seat was a significant factor contributing to injury. We found that seats failed the passengers in three principal respects: by being too weak; too low; and too hostile. In response, we developed requirements to improve the performance of school bus seats and the overall crash protection of school buses. Those requirements comprise the "compartmentalization" approach we adopted for providing high levels of crash protection to school bus passengers.

Compartmentalization is directed toward ensuring that passengers are surrounded by high-backed, well-padded seats that both cushion and contain the children in a crash. If a seat is not compartmentalized by a seat back in front of it, compartmentalization must be provided by a restraining barrier. The seats and restraining barriers must be strong enough to maintain their integrity in a crash yet flexible enough to be capable of deflecting in a manner which absorbs the energy of the occupant. They must meet specified height requirements and be constructed, by use of substantial padding or other means, so that they provide protection when they are impacted by the head and legs of a passenger.

It is helpful to bear in mind the following highlights about compartmentalization:

  1. Compartmentalization provides effective occupant crash protection, minimizes the hostility of the crash environment and limits the range of movement of an occupant, without using seat belts;

  2. Compartmentalization ensures that high levels of crash protection are provided to each passenger independent of any action on the part of the occupant; and,

  3. Seat belts are needed on passenger cars and other family vehicles and on small school buses (school buses with a GVWR of 10,000 pounds or less) because the crash pulse, or deceleration, experienced by the lighter vehicles is more severe than that of larger vehicles in similar collisions. Large school buses are inherently safer vehicles because they are larger and heavier than the vast majority of the other vehicles on the road. In addition, occupants in large school buses sit above the forces that are typically imparted to the bus by smaller impacting vehicles during a crash. The training and qualification requirements for school bus drivers and the extra care taken by other road users in their vicinity add to the safety of school buses.

With this background in mind, we now turn to your questions.

  1. Does the Busbelts Development Corporation's integrated shoulder belt and/or occupant restraint system meet all applicable FMVSSs?

Because the BDC system is an item of equipment that is sold separately from a school bus, there are almost no safety standards that directly apply to it. Our safety standards for school buses apply to new, completed vehicles, not to separate components systems such as the bench seat and integrated belt system. As such, Standard No. 222 does not apply to the BDC product, assuming the product is sold in the aftermarket and is not sold as part of a new school bus. Our standard for seat belt anchorage strength (Standard No. 210) also applies to new, completed vehicles. A representation that a product meets crash protection standards that do not apply is misleading.(2)

The only safety standard that applies to the aftermarket product is Safety Standard No. 209, Seat Belt Assemblies. Standard No. 209 specifies strength, ease-of-use and other requirements for seat belt webbing, buckles, and other components. Section S4.1(c) of Standard No. 209 requires that a lap-and-shoulder belt system (a "Type 2 seat belt assembly") must provide upper torso restraint without shifting the pelvic restraint into the abdominal region. Some of the photographs you provided depict children wearing the Type 2 seat belt with the lap portion in the middle of their bodies, above the pelvic region. Placement of the lap portion of the seat belt in the abdominal area of a passenger is prohibited by S4.1(c). A belt positioned over the abdominal area will load the abdomen in a crash, resulting in a greater likelihood of injury to the abdomen and surrounding organs.

It appears from some of the photographs that the lap belt is pulled on to the abdominal area of some of the children by a device that adjusts the positioning of the lap and the shoulder belts on small children. We refer to these types of devices as "belt positioning devices." Due in part to our concerns about positioning a lap belt over a child's abdominal area and about how some devices introduce excessive slack into the shoulder belt, we recently began a rulemaking action to regulate these devices. We issued a notice of proposed rulemaking (NPRM) proposing to require belt positioning devices to be labeled with a warning not to use them with children under a certain size (e.g., a child smaller than the average 6-year-old), and not to have the lap belt positioned over the child's abdomen. A copy of our NPRM is enclosed for your information.

If the BDC system were installed on new school buses, the vehicle would have to meet Standard No. 222 and the other school bus standards with the product installed. Without testing a vehicle, we cannot make a positive determination of whether the standard could be met with the product installed. However, as explained below, we believe that a new school bus may not be able to meet the standard with the seating system. We have other safety concerns as well, apart from whether the requirements of Standard No. 222 could be met.

  1. Would retrofitting a school bus with the Busbelt integrated shoulder belt system make the school bus no longer meet Standard No. 222?

We believe it is possible that the incorporation of a shoulder belt into existing school bus seats would reduce the benefits of compartmentalization. As we explained in the background section, Standard No. 222's compartmentalization requirements rely on the school bus seat backs to help cushion and contain the occupants in a crash. Each seat back protects not only the occupant of that seating position, but also the occupant seated rearward of that seating position. If a shoulder belt were attached to a school bus seat back, the belt may prevent the seat back from deflecting forward in the manner required by S5.1.3 of Standard No. 222 to protect the rearward passenger. In other words, in a crash the seat back will not perform in a manner that would provide protection to an unrestrained passenger.

Even if the seat back deflects as required by Standard No. 222, it is possible that compartmentalization could be compromised by the attachment of a shoulder belt to a school bus seat back. These relate to possible problems resulting from a load application of two different forces on the school bus seat in a severe crash. In a forward collision, a passenger restrained by the shoulder belt would load the belt at an earlier point in time than the point at which the seat back is impacted by an unbelted occupant seated directly rearward of the seat. The forward force on the seat back from the shoulder belt would tilt the seat back forward prior to the impact of the rearward unbelted occupant against the seat back. The unbelted occupant would ramp up the tilted seat back in the crash, rather than be contained in what had been a compartmentalized space. That occupant not contained in the compartment would be at greater risk of injury due to possible ejection and/or impacts against hard or unforgiving surfaces.(3) Both the head of the unrestrained passenger and the head of the restrained passenger could impact, possibly injuring both children.

The head of the unrestrained passenger could impact the head of the restrained passenger, resulting in possible injury to the two passengers.

Compartmentalization could be compromised in other ways as well. The seat backs of school buses must meet head protection requirements specified in S5.3.1. The performance requirements in S5.3.1 generally lead manufacturers to pad their seat backs with energy-absorbing foam and to ensure that there are no hard structures in the seat back that can cause head injuries to the passenger rearward of the seat back in a crash. Anchoring a shoulder belt to the seat back may require the installation of rigid components, which may cause the seat back to no longer meet S5.3.1.

The seat backs must also meet leg protection requirements specified in S5.3.2 of Standard No. 222. The requirements are generally met by padding and other measures to protect passengers' knees as they impact seat backs in a crash. Apparently BDC modifies the school bus seat by installing a cross bar and D-ring structure to mount the belts and by installing a steel lap and shoulder belt retraction system within the seat back. The knee and leg protection requirements of the standard must continue to be met with the retrofitted components in the seat back.

In addition to the issues discussed above, care should be taken to ensure that passengers will not be entangled in the shoulder belt webbing material in a crash. Shoulder belts that have a considerable amount of webbing around the head and neck area of children pose a risk of strangulation or other neck injuries.

For the above reasons, we believe that a school bus seating system with an integrated lap and shoulder belt system might reduce the crash protection provided by compartmentalization. (4) There is limited information about how an integrated lap and shoulder belt system on a school bus seat would perform in a crash or affect the current safety of school buses. We are undertaking a comprehensive school bus safety research program to evaluate better ways of retaining occupants in the seating compartment. As part of that program, we will be looking into possible ways of redesigning the school bus seat as well as integrating a lap and shoulder belt into the seat that is compatible with compartmentalization. Also, we plan on conducting some research on extra padding, not only for the seat itself but also for the bus side wall. Information from this research program will help researchers better understand and develop the next generation of occupant protection systems for school buses.

  1. Would retrofitting a school bus with an integrated shoulder belt system make inoperative the bus's compliance with FMVSS 222?

Section 30122 of our statute prohibits a motor vehicle manufacturer, dealer, distributor, or repair business from installing any modification that "make[s] inoperative any part of a device or element of design installed on or in a motor vehicle in compliance with an applicable motor vehicle safety standard . . . ." Any person in the aforementioned categories that makes inoperative the compliance of a device or element of design on the vehicle would be subject to fines of up to $1,100 per violation and to injunctive relief.

The compartmentalization requirements of Standard No. 222 include requirements that a protective seat back must be provided to protect an unrestrained passenger. We believe that replacing a school bus seat with a seating system that has a torso belt is likely to make inoperative an element of design installed as part of the compartmentalization concept. We are concerned about the continued compliance of the bus with Standard No. 222's seat deflection and head and leg protection requirements. We are concerned about the ability of the bus to continue to provide required crash protection to children regardless of whether a belt is used.

  1. If a school bus were retrofitted with the Busbelt integrated shoulder belt system, will the school bus continue to meet all applicable Federal motor vehicle safety standards?

Compartmentalization is intended to restrain passengers in a crash regardless of whether they buckle up. A torso belt may reduce that level of safety to an unbelted passenger. As previously stated, we have concerns about a product that might interfere with the ability of a school bus to protect unbelted occupants. We will be evaluating integrated lap and shoulder belt systems in our school bus research program. The program will provide information that will help us better assess the merits, costs and feasibility of having integrated seat belts on school buses.

Before closing, we wish to address a statement that BDC made in its marketing literature in support of seat belts on large school buses. BDC states that its "dynamic test data" shows that in a 30 mile per hour (mph) school bus crash, an unbelted occupant "suffered fatal head injuries (2000 HIC level) when his/her head came in contact with a standard school bus seat." These test data apparently result from computer simulations conducted for BDC. The data do not reflect the data we have obtained in actual crash testing of school buses. Actual crash test data from a 30 mph barrier crash conducted by NHTSA indicate that HIC measurements recorded by calibrated test dummies are all well below the 1,000 threshold level.

On a final note, we would like to point out that many of your newer school buses may still be under the school bus manufacturer's warranty. Before you decide to retrofit any school bus with any seat belt, it may be prudent for you to share BDC's information with the school bus manufacturer, and request a determination whether the school bus manufacturer will continue to honor warranties if the BDC seat belts are placed on school buses.

I hope this information is helpful. If you have any further questions, please feel free to contact Dorothy Nakama of my staff at this address or by telephone at (202) 366-2992.

Sincerely,
Frank Seales, Jr.
Chief Counsel
Enclosure
ref:222
d.10/28/99

1. We note that this statement is misleading. NHTSA does not "certify" or "approve" test laboratories or facilities to conduct compliance testing or for any other purpose.

2. Regardless of whether a safety standard applies to the product, our statute at 49 U.S.C. 30120 requires manufacturers of motor vehicles and motor vehicle replacement equipment to provide remedies if it is determined their products have safety-related defects. If it were determined that the seating systems had a safety-related defect, the manufacturer would have to notify all purchasers and repair or replace the defective item without charge.

3. Another concern associated generally to the use of lap and lap and shoulder belts on large school buses relates to the potential for seat failure resulting from combined stresses exerted simultaneously or in close succession on a school bus seat by: (1) the belted occupant of the seat, where the seat belt is attached to the seat frame; and (2) an unbelted occupant, seated directly rearward of the seat, impacting the seat back. In a severe crash, the combined force applications on a particular seat resulting from a belted occupant and an unbelted occupant in the rearward seat could increase the likelihood of seat failure or seat deformation. We do not believe that school buses are frequently involved in the type of severe frontal crashes where this phenomenon is likely to occur. However, there is a risk that compartmentalization could be compromised in this circumstance.

4. The concerns discussed above relating to the compatibility of compartmentalization with existing designs of lap and shoulder belts also apply to the situation where a belt system is retrofitted to existing school bus seats (i.e., where the original bench seat is modified but not replaced).