1999 Chevrolet Express Van Owner's Manual - Page 202

yellowblue Hazard Warning Flashers Push the button at the top of the steering column all the way down to make your front and rear turn signals flash on and off. Your hazard warning flashers work no matter what position your key is in, and even if the key isn't in. To turn off the flashers, push the button until the first click and release. Your hazard warning flashers let you warn others. They also let police know you have a problem. Your front and rear turn signal lamps will flash on and off. When the hazard warning flashers are on, your turn signals won't work. 5-2