You have to use the mirrors. If you turn around, all you see is the front of the trailer.
I live at the end of a small cul-de-sac. My truck has a hard time making the 180* turn to back in to my driveway (trash trucks have a hell of a time in there!). Instead of tight turning my trailer, I just back up the road directly into my drive. As soon as I get straight, all I can see is down each side. I will slightly zig-zag as I back up the road so that I can see 'behind' the trailer better. Been working for years. No little kids on my street except for mine so it's a win!