I am assuming you are referring to ground driving. There are many benefits to doing this, especially for young horses. This is a great way to get them used to the bit and learning to respond to cues when they can't see you. Most of the time when you are training young horses, you are right by their head teaching them to lead, longe, etc. Driving teaches them that they have to respond to your cues even when they can't see you. It is not really dangerous, but it is easier to start with two people when you are doing it with a horse for the first time. All you really need is two lunge ropes and clip them on to the side rings of a halter or a snaffle bit. Some people use a surcingle and others will run them through the stirupps of the saddle. Of course your horse needs to be used to a saddle first. You can also do this on older horses.