Backing up
I can't help you with your particular application, but my company of 600+ employees has the policy that every employee must review every accident (OSHA recordable, lost time, contractor accidents, motor vehicle accidents, etc.) and a clear pattern has emerged - most motor vehicle accidents involving company and contractor vehicles occur while backing up. There have been some really amazing accidents while backing up!
Furthermore, they have recently implemented a policy in which before backing up in a company vehicle there must either be a spotter or the driver must do a complete walk around. Failure to use one of these two methods could result in a two day suspension without pay.
I've been fortunate over the years and only backed into 1 tree that was clearly in my rear view, but I was too busy watching the side mirrors to notice it. I've had numerous close calls and subscribe to my company's policy and like chnlisle will get out and look, even if I "know" what is behind me.