Journal of Accident Investigation

Figure 13. The heavy truck relative to the side of
the school bus after impact.
The seating positions of the dummies are shown in figure
14. As in the frontal crash tests, the Hybrid III th female
and 6-year-old dummies were used. Replacing the Hybrid III
0th male dummies were two 0th male side impact dummies
(SID), which are capable of measuring lateral head, chest, and
pelvic accelerations. One of the SID/Hybrid III dummies was
positioned a row behind the direct impact zone of the truck
(position 2 in figure 14). One Hybrid II 0th male dummy with
a single triaxial accelerometer array in the head was centered at
the point of impact to determine survivability within the impact
zone (position 1 in figure 14).
Figure 14. Positions of the dummies in the side impact crash scenario.
Table 3 shows the results for the side-impact crash test. HIC
values were based on a 1 -msec duration, and chest acceleration
values were based on a 3-msec duration, with the same pass/
fail criterion as in the frontal tests. For the SID dummies, the
Thoracic Trauma Index (TTI) was also recorded. A value of
OCCUPANT SAFETY IN LARGE SCHOOL BUSES
Table 3. Side impact test results.
Dummy HIC Chest G TTI
#1 (HII) 2164 N/A N/A
#2 (SID) 277 N/A 54.7
#3 (5th F) 85 27.7 N/A
#4 (6 yo) 124 11.1 N/A
#5 (SID) 133 N/A 7.1
#6 (6 yo) 54 22.7 N/A
#7 (5th F) 1 7.4 N/A
8 g indicated the onset of serious injuries and served as a pass/
fail criterion under FMVSS No. 214. 12
The head injury criterion was exceeded for the dummy
centered in the impact region. All other injury criteria were
below the thresholds.
The two crash tests conducted for this program represented
severe crash conditions. In general, school bus mass
effectively minimizes the acceleration forces experienced in a
vehicle-to-vehicle crash with most passenger vehicles. The
potential acceleration loads from frontal and rear crashes with
vehicles of similar mass are also effectively minimized by the
manner in which the body of the bus is coupled to the chassis of
the bus. The frontal crash test demonstrated that, by allowing
the body to slide along the frame of the bus, much of the
kinetic energy of the bus could be dissipated before loading the
passenger compartment.
In a side impact, the construction of the body of the bus
does very little to prevent passenger compartment intrusion.
However, due to the high ground clearance of the school
bus, passenger vehicles are not a serious threat in generating
passenger compartment intrusion. Vehicles large enough to
pose a significant probability of intrusion are of a sufficient mass
that no feasible body structural design will effectively prevent
them from intruding into the passenger compartment.
In the test, passenger compartment intrusion at the point of
impact was severe. The high degree of deformation at the point
of impact was very effective at absorbing and dissipating the
energy of that impact. The side impact test conducted for this
program showed that an occupant seated only a few feet outside
12 Code of Federal Regulations, Title 49, Chapter V–National Highway Traffic
Safety Administration, Department of Transportation, Federal Motor
Vehicle Safety Standard No. 71.214; Side Impact Protection.
NTSB JOURNAL OF ACCIDENT INVESTIGATION, SPRING 2006; VOLUME 2, ISSUE 1 63