Lexus RX300 2003 Owner's Manual page 149

16R291
D If the driver's seat position does not allow sufficient
space for safe installation, install the child restraint
system on the rear right seat.
16R341
"
Same position
1 2
D When installing a child restraint system in the rear
center position, align both seat cushions to the same
position and align both seatbacks at the same angle.
Otherwise, the child restraint system cannot be
securely restrained and this may cause death or
serious injuries in a collision.
Same angle