The blind person (sometimes called a "handler") and the dog need to work together. Both the dog and the handler must take special training to learn how to work as a team. The handler needs to let the guide dog know the direction they want to go. The dog can lead the person around things that may be dangerous, such as moving cars or other things. Also, guide dogs may be taught to press buttons to work elevators or get things for their handler. Because dogs cannot see colors as well as people, they cannot read traffic signals, so the handler must use ways to tell if it is safe to cross a street.