5. TEST METHODOLOGY
Tests were performed with three state-of-the-art fully instrumented dummies. Two dummies were selected to represent preschool-aged children, while one represented a small school-aged child. These dummies and the size of children they represent are presented below.
The head and chest accelerations of the dummies were measured for each test. Because injury reference levels have not been adopted for children,19 the upper and lower neck forces and moments and shoulder loads were not analyzed.
Two tests each were conducted for the 18-month dummy using compartmentalization and child restraints, two tests each were conducted for the 3- and 6-year old using compartmentalization, and three tests were conducted for the 3-year old using child restraints.
5.1 Test Facilities
School bus seats meeting CMVSS 22220,School Bus Passenger Seating and Crash Protection were installed and secured to a HyGe sled. In the case of compartmentalization tests, a cage was installed around the test equipment to retain the dummies.
Figure 1 - Typical test setup
The tests were conducted in accordance with the prescriptions of -Test Method 213 - Child Restraint Systems.”21 The change of velocity of the test sled (dV) was 48 km/hr , while the deceleration pulse of 20 g was attained within 11 milliseconds and maintained until 48 milliseconds after the start of the test. The ambient test conditions, specifications for atmospheric soaking and test preparation, were also those specified in the Test Method.
5.2 Test Dummies
The 18-month CRABI22 and 3-23 and 6-year24 Hybrid III dummies were used in this test program. The mass for each dummy is given in Table 1.
The 18-month dummy represents a child whose mass is slightly over that of an older Stage 1 child (from birth to about one year old), the 3-year dummy that of a Stage 2 child (from about one year to about 4½ years) and the 6-year dummy that of a young Stage 3 child (from about 4½ to about eight years). The stages corresponding to the dummy sizes used in this study are also given in Table 1.
Table 1 - Test dummy information
|
Test Dummy |
Mass ( kg ) |
Mass ( lb. ) |
Corresponding Stages in Car Time 1-2-3-4 |
Targeted bus occupant population |
|
CRABI 18-month |
11.5 |
25.3 |
Slightly above that of Stage 1 |
Smallest-size child potentially taking part in daycare activities and trips |
|
3-year Hybrid III |
15.5 |
34.0 |
Stage 2 |
Average-size child potentially taking part in daycare activities and trips |
|
6-year Hybrid III |
23.5 |
51.6 |
Stage 3 |
Youngest grade school child transported on school buses |
The specifications for the head and chest accelerometers that recorded the data analyzed in this report are consistent with Society of Automotive Engineers Recommended Practice SAE J211.25 The dummies were clothed as specified in Test Method 213, with clothing size adjustments made for their respective stature.
5.3 Restraints
Every school bus seat and child restraint used in this testing was either a commercially available product or a prototype designed by seating or restraint manufacturers.
Footnotes
19 United States Federal Register: Rules and Regulations; FMVSS 213 – Child Restraint Systems, Vol. 68, No. 121, June 24, 2003; pp. 37619-37658.
20 SOR/80-161, February 21, 1980; SOR/86-453, April 17, 1986; SOR/91-593, October 24, 1991.
21 Issued April 1, 1982, and revised in October 2001.
22 CRABI 18 Month Old Child Dummy, First Technology, part no. 93091-000.
23 United States Code of Federal Regulations, Title 49, Transportation, Part 572 – Sub-Part “P.”
24 United States Code of Federal Regulations, Title 49, Transportation, Part 572 – Sub-Part “N.”
25 Society of Automotive Engineers Recommended Practice (SAE) J211, Instrumentation for Impact Tests (MAR95).