Step-by-step Reversing

This example describes how to reverse to the left because that is easier than reversing to the right. 

If you are not sure which way your wheels are pointing at any time lean out and look at them.

Many pre-1989 trailers have a lever that prevents the brakes from operating during reversing. 
All braked trailers built after March 31st 1989 have auto-reverse brakes.

1 ) Start with the outfit as straight as possible and about a trailer's length from the place into which you are reversing. You need plenty of room to swing the towcar round.
		2 ) Watching the trailer out of the driver's window, reverse slowly and start turning the steering to the right. It is easier to add more steering than to correct too much.
3 ) As soon as the trailer starts to turn, you begin straightening up whilst still reversing. If you leave it too late, the trailer will 'jack-knife'. (This means that it gets to such an acute angle to the towcar that it can no longer be manoeuvred in reverse. This condition can damage towcars with long rear overhangs).
		4 ) Eventually you start steering the other way, while still reversing, to bring the towcar's nose round so that the car "follows" the trailer – but keep an eye on where the trailer is going in case it needs correction

5 ) Reverse in a straight line using the door mirrors. Reverse slowly and carefully. When more of the trailer starts to appear in one mirror, steer towards that mirror to start the trailer going the other way. Such corrections only require small steering movements.

6 ) Do not get your mind stuck in reverse! If the trailer goes out of line, it may be easier to pull forward to correct it. On tight turns or if it jack-knifes, to pull forward is your only option.

NTTA have a nice "Interactive Demo"