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NOTES ON NTSB PUBLIC
MEETING OF 9-21-99 ON HIGHWAY SPECIAL INVESTIGATION: BUS CRASHWORTHINESS
My initial
impression of the meeting is that the NTSB report will be flawed but more
useful than not.
The language of
the conclusions and recommendations is particularly useful while the
presentation by staff and subsequent remarks during the press conference
by staff and Mr. Osterman were negative towards seat belts on school
buses.
First the good
news:
The conclusions
and recommendations related to school buses are these:
- In the
accidents analyzed for this special investigation, school bus
passengers who remained within the seating compartment but not within
the intrusion area during the accident sequence were less likely to
have been seriously injured than passengers who were out of the
compartment before the collision or who were propelled from the
compartment during the collision.
- Because of
compartmentalization, school bus passengers are safer now than they
were before 1977.
- Current
compartmentalization is incomplete in that it does not protect school
bus passengers during lateral impacts with vehicles of large mass and
n rollovers, because in such accidents, passengers do not always
remain completely within the seating compartment.
- All potential
designs for occupant protection systems to be used on school buses
should be tested to uniform performance standards developed by the
National Highway Traffic Safety Administration to ensure occupant
safety.
- It cannot be
determined whether the current design of available restraint systems
for large school buses would have reduced the risk of injury to the
school bus passengers in the accidents simulated for this special
investigation.
- The potential
exists for an occupant protection system to be developed that would
protect school bus passengers in most accident scenarios.
- One of the
primary causes of preventable injury in motorcoach accidents involving
a rollover, ejection, or both is occupant motion out of the seat
during a collision when no intrusion occurs into the seating area.
- The overall
injury risk to occupants in motorcoach accidents involving rollover
and ejection may be reduced significantly by retaining the occupant in
the seating compartment throughout the collision.
- New occupant
protection systems for motorcoaches should be tested to uniform
performance standards developed by the National Highway Traffic Safety
Administration that are based on actual crash testing of motorcoaches
to ensure occupant safety.
- Equipping
motorcoach side windows with advanced glazing may decrease the number
of ejections of unrestrained passengers during motorcoach accidents
and decrease the risk of serious injuries to restrained passengers
during motorcoach accidents.
- Because the
increased size of passenger windows in motorcoaches may affect roof
strength, rollover strength standards must be developed to take into
account the effect of typical window dimensions.
- The Department
of Transportation does not have standard definitions or
classifications for the various bus types.
- The Fatal
Accident Reporting System (FARS) is not a reliable source for
identifying the number of fatal occupant ejections in motorcoaches.
- The
incorporation of bus identification into the vehicle identification
number and the expansion of the use category will correct some of the
inaccuracies of the FARS data, but without standard definitions and
accurate classification of buses within FARS, incomplete data and
inaccuracies will still exist.
- The Model
Minimum Uniform Crash Criteria do not provide specific enough guidance
to the States of bus body type coding.
- School bus
accident injury data are incomplete, and, therefore, injuries cannot
be reliably estimated.
- The use of
onboard recorders may help reduce the accident rates of vehicle
fleets.
- On-board
recorders are needed to provide quantitative data to evaluate the
dynamics of bus crashes.
- Establishing
on-board recording standards for highway vehicles will provide a
necessary foundation for the future use of on-board recorders.
Safety
Recommendations
To the Department
of Transportation
- In one year
and in cooperation with bus manufacturers, complete the development of
standard definitions and classifications for each of the different bus
body types, and include these definitions and classifications in the
Federal Motor Vehicle Safety Standards.
- Once the
standard definitions and classifications for each of the different bus
types have been established in the Federal Motor Vehicle Safety
Standards, in cooperation with the National; Association of Governor’s
Highway Safety Representatives, amend the Model Minimum Uniform Crash
Criteria’s bus configuration coding to incorporate the FMVSS
definitions and standards.
To the National
Highway Traffic Safety Administration
- In two years,
develop performance standards for school bus occupant protection
systems that account for frontal impact collisions, side impact
collisions, rear impact collisions, and rollovers.
- Once pertinent
standards have been developed for school bus occupant protection
systems, require newly manufactured large school buses to have an
occupant crash protect5ion system that meets the newly developed
performance standards and retains passengers, including those in child
restrain systems, within the seating compartment throughout the
accident sequence for all accident scenarios.
- In 2 years,
develop performance standards for motorcoach occupant protection
systems that account for frontal impact collisions, side impact
collisions, rear impact collisions, and rollovers.
- Once pertinent
standards have been developed for motorcoach occupant protection
systems, require newly manufactured motorcoaches to have an occupant
crash protection system that meets the newly developed performance
standards and retains passengers, including those in child restraint
systems, within the seating compartment throughout the accident
sequence for all accident scenarios.
- Expand your
research on current advanced glazing to include its applicability to
motorcoach occupant ejection prevention, and revise window glazing
requirements for newly manufactured motorcoaches based on the results
of this research.
- In 2 years,
develop performance standards for motorcoach roof strength that
provide maximum survival space for all seating positions and that take
into account current typical motorcoach window dimensions.
- Once
performance standards have been developed for motorcoach roof
strength, require newly manufactured motorcoaches to meet those
standards.
- Modify your
methodology to collect accurate, timely, and sufficient data on
passenger injuries resulting from school bus accidents so that
thorough assessments can be made relating to school bus safety.
- Require that
all school buses and motorcoaches manufactured after January 1, 2003 ,
be equipped with on-board recording systems that record vehicle
parameters, including, at a minimum, crash pulses for determining bus
body motion. (Additional recorder parameters will be added. The
additional language will be presented to the Board for approval at a
later date.)
- Develop and
implement, in cooperation with other Government agencies and industry,
standards for on-board recording of bus crash data that address, at a
minimum, parameters to be recorded, data sampling rates, duration of
recording, interface configurations, data storage format,
incorporation of fleet management tools, fluid immersion
survivability, fire survivability, independent power supply, and
ability to accommodate future requirements and technological advances.
To the National
Association of Governor’s Highway Safety Representatives
- In conjunction
with the Department of Transportation, amend the Model Minimum Uniform
Crash Criteria’s bus configuration coding to comply with standard
definitions and classifications of buses.
To the bus
manufacturers
- Cooperate with
the Department of Transportation in the development of standard
definitions and classifications fort each of the different bus body
types.
On to the bad
news:
The staff focused
on the potential for lap belt and lap/shoulder belt induced injuries. This
position is based on their computer simulations. Essentially, they are
saying that in a large bus the passengers at the front and rear of the bus
are sufficiently far from the center of gravity of the bus that they are
subjected to severe forces when the bus rotates. Further, they say that
those forces pinion the pelvis to the seat and impart a whip like motion
to the upper body which results in high head loadings taking place. They
posit that these loadings will cause injury. (This is the same argument
that has been used against seat belts for years, but there are no
significant real world instances where belts have caused these kinds of
head injuries. Or where the passenger would have suffered much worse
injuries without the belt.)
Interestingly,
they also say that the sideways forces experienced by these passengers
will result in even lap/shoulder belted passengers being subjected to
similar whip like head loadings because the passenger who is thrown toward
the aisle will slip out of the upper body restraint and will then be
subject to similar forces as the lap belted passenger. (The passenger will
slip out of the shoulder belt when thrown toward the aisle because
shoulder belts go over the outboard shoulder.)
Dr. Yeager points
out that while it may be true that passengers farther from the center of
gravity will be subjected to strong rotational forces, passengers on a
spinning small bus will probably suffer similar forces because the crash
pulse is stronger in the lighter vehicle.
Mr. Osterman
confirmed that the NTSB had looked aggressively for belt induced injuries
in large buses and was unable to find any.
The computer
modeling on which so many of the negative remarks about lap and
lap/shoulder belts are based may or may not be accurate. Some of the
software used was provided/developed by NHTSA which has been
obstructionist at best. The initial technical draft we were able to review
was appalling in its inaccuracies and inconsistencies. It is possible that
the staff has cleaned up the report, but we won’t know until we see the
published report in 2-3 months.
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Rebuttals
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