NHTSA Motorcoach Roof Crush and Rollover Testing

[davidbrady]

From the "Discussion Paper":

"The FMVSS No. 220 test applies a uniformly distributed compressive load (equivalent to 1.5
times the unloaded vehicle weight of the bus), on the roof of the bus along its longitudinal
centerline using a 915 mm (3 feet) wide platen that is 305 mm (1 foot) shorter than the bus length.
The requirements are that the bus roof does not compress more than 130 mm (5.118 inches) and
the emergency exits remain operable. It was determined that the test protocol could be adapted to
test motorcoaches with only minor changes to the test device. However, neither the MCI nor the
Prevost bus was able to meet the 1.5 times the unloaded vehicle weight (UVW) required for
school buses. The MCI bus was able to achieve 0.91 x UVW prior to the front of the bus
collapsing and hydraulic test device running out of stroke. The Prevost bus was able to achieve
1.17 x UVW prior to the front of the bus collapsing and hydraulic test device running out of
stroke. It should be noted that neither of these buses were required or designed to meet the
FMVSS No. 220 requirements".

Methinks their performance in the School Bus crush test, FMVSS No. 220, is pretty remarkable given that they weren't designed to meet this standard. :-)

The unloaded vehicle weight (UVW) for the MCI is 27853# and for the Prevost 29270#. The UVW of a 36' Blue Bird All American School Bus is 18880#, from here, (or 20977# if we extrapolate this weight out to a 40 footer). For a 40' school bus to pass FMVSS No. 220 it must support 1.5*20977= 31466#. The MCI supported 0.91*27853 = 25346# and the Prevost 1.17*29270 = 34246#. (This doesn't say what the All American can support before crushing excessively, just what it needs to).