Memorandum - NHTSA

Iv-33
S6.10.2.3 - The lift can not be stowed if an occupant (with or without mobility aid) is on the
platform.
S6.10.2.4 - The lift can not move up or down unless the inner roll stop is deployed in the verti .:a1
direction.
S6.10.2.5 - The lift can not move up or down [when the lift is greater than 76 mm (3") above the
ground) unless the WC retention device, normally an outer barrier, is deployed in the vertical
direction.
S6.10.2.6 - With the lift at ground level, if the lift is equipped with an outer barrier, it can not
deploy if occupied by a lift occupant or mobility aid/occupant. This interlock recognizes if a
cane, foot or WC/occupant is on the inclined plane that becomes the WC retention device. This
eliminates or avoids the accident scenario of tripping an elderly person with a cane or flipping the
WC and its occupant over.
S6.10.2.7 - The inner roll stop will not deploy if occupied by a lift occupant or mobility
aid/occupant. As with S6.10.2.6, this interlock recognizes that a cane, foot or WC/occupant a .e
in contact with the inner roll stop. This eliminates or avoids the accident scenario of tripping in
elderly person with a cane or flipping the WC and its occupant over.
Lift Interlock Rationale
The Final Rule requires that all lift controls be located together and in a position where the
control operator has direct unobstructed view of the lift passenger, and/or any wheelchair,
throughout the range of lift operation. This is generally the case today. Advertisements for
school bus lifts (called active lifts), for example, show the lift operator outside the bus, standi~g
next to the lift passenger, with the lift remote controls in-hand. For a transit bus with a passiv.:
lift (front door steps fold to make a platform), the driver is already in full view of the lift user.
Although based on anecdotal information, situations have occurred where the operator has
improperly operated the lift resulting in lift passenger injuries and fatalities. These cases have
been discussed earlier in the report. One theory is that even though the passenger was probab y
fully visible to the operator, the operator may not have been aware of the passenger's presence.