Once a horse is in the habit of breaking away from crossties, it is very difficult to correct this vice. Although safety latches can prevent a struggling horse from incurring serious injuries--that is, head and neck injuries from strain, head and spinal injuries from flipping over backwards in the cross ties, etc.--too often they encourage a horse to break away whenever it wants if the horse readily perceives how easy it is to do so.
The key to solving this problem, then, is to make it easy for the horse to stay tied and difficult for it to break away. First, avoid cross-tying your horse in an aisle (which offers an obvious front and rear escape) and, instead, tie the animal in a stall or rubber-matted wash stall that provides a barrier both in front of the animal and behind its haunches. Second, provide a full haynet where the horse is tied so that the animal has an incentive to stay in place. Third, use a regular halter and lead rope, but tie the horse up with a slip knot so that you can quickly release it if the animal begins to seriously struggle. Fourth, only keep the horse tied up for short periods of time--no more than five minutes to begin with--so that it doesn't become bored or anxious. Fifth, make sure you don't tie the horse if it already seems keyed up. For example, avoid tying by getting someone to hold the horse while you tack up; then attempt to tie the horse for a short period when the animal is tired after work. Sixth, make sure the horse has plenty of turnout every day. Nothing makes a horse giddier than to be locked in a stall all day.