Have you taught your dog how to stop dead in his tracks in the event of an emergency? What would you do if your dog was just about to run into a busy street? Maybe he has seen a deer or another dog and has started to chase after him. In all of these situations, your dog is at risk of serious injury or worse if you can't get him under control – and do so very quickly. The idea is for you to be able to make your dog stop and drop instantly, using a single verbal command or hand signal at any time, no matter what he is doing.
The command is basically the same as drop on recall, you could use "Drop" or "Stop" and a single down sweeping motion of your hand. It really doesn't matter as long as you teach your dog that he must drop instantly the moment he sees or hears the command. He doesn't even need to know why, just that he must obey immediately. This is a very important command as it could very easily save him from being badly injured, dying, or getting lost.
Training your dog to emergency stop is no more difficult than teaching him to drop on recall. But it will take time and patience, and a large supply of his favorite treats. You can teach a dog of any age this very important command, but it may take longer with younger pups as they are a little more wound up. But if you have already taught your dog to drop on recall, it will go much easier. Remember to give your dog plenty of praise and treats when he gets it right and never punish him when he gets it wrong.