Dogs can sometimes be able to make sure cars aren't coming but aren't always able to judge is there is enough space to make it for a oncoming car. They can't be expected to be 100% reliable on this. However you can teach them to stop at every crosswalk and street corner and not proceed uness you give a command. Some dogs can be taught to stop and not proceed when a car is coming but I would put 100% trust in them. It really tasks a special observant dog to do this.