And, if someone is behind your trailer, no need to worry about hitting them changing
lanes, they are behind you
But, towing mirrors do help a lot.
You didn't ask about backing up which is a skill all in itself, but hopefully you've got some experience. I find having my DW either guide or drive is very helpful as I'm only into my TT a handful of trips so far and not being able to see back there is worrysome, so I use a spotter. I don't care if I look like a newbie, rather not hit anything! A lot of of the spots I've been into are a bit tight.