Winseer:
I thought there were fancier sat navs that said warnings of low bridges to the level you punch into the device?I’ve always thought that the reason Truck drivers use SatNavs out of a Christmas Cracker - was they are too cheapskate to buy a proper one.
Still doesn’t excuse not knowing the height of your trailer though…
Sat navs are just an aid, mark 1 eyeball should be used at all times (though I concede that if there aren’t any brain cells behind it, it’s more than useless 
).