Lift Truck operators must look in the direction of travel so, in reverse, they must turn around - arm around the back of the seat where possible, swivel at the waist and look in the direction of travel.
Having said that, it has been stated that operators do not turn around until they have backed up 2-7 feet. A problem that needs to be addressed with some operators.
Operators must not look in a mirror when they are backing up, but as Mark stated, the problem is when they deposit/retrieve a stacked pallet. Their attention is on their forks/load until they back up far enough to clear the stack or racking.
I advise operators that when they put their truck in reverse and before they take their foot off the brake; turn around to both sides and check behind them and then sound their horn. Now they can concentrate a little better on their forks or load as they back up and clear the stack or racking. Once clear, they lower their forks to the travel position and turn around properly for reverse driving.
It is during this say 4 foot back up that is critical and this is where mirrors play a role.
A driver that checks behind before they start to back up and now concentrating on their load for this 4 foot back up can take a quick look in the mirror to assist them in ensuring no one is behind them.
As stated earlier, I too prefer the panoramic mirrors to assist them.
Pedestrians need to be told of this critical danger zone - the first 7 feet of back up and to stay at least this far from the rear end of a lift truck. Further, pedestrians need to be told to make "eye contact" with a lift truck operator before approaching - from any angle. If they haven't, the operator doesn't know they're there, so stay away.
If mirrors are being misused for back up, that's where supervisors and all management people need to become involved and speak to the driver to correct their error.
Seats are now available that swivel about 17 degrees to the right to assist an operator for back up and reduce neck/shoulder discomfort.