Get out of the lane
At the first sign of trouble, signal right and move toward the shoulder. If you can make it to an exit or a safe parking lot, do so. The shoulder of an interstate is genuinely dangerous; passing trucks at 75 mph create air pressure that can move you and debris that can hit you.
Make yourself visible
Once stopped, turn on your hazard lights immediately. If you have a reflective triangle or flares, place them 100 to 300 feet behind the car so approaching drivers see them in time to move over.
Stay or go?
On a busy highway, the safest place is usually outside the car and well off the shoulder, behind a guard rail if one is available. The cabin of a car parked on a highway shoulder is one of the most dangerous places to sit. In bad weather or on a quiet road, staying in the car may be safer — judgment call.
Call for help
Call your roadside assistance, your insurance roadside service, or 911 if you are in immediate danger. Give the dispatcher your direction of travel and the nearest mile marker or exit. Do not accept help from strangers who pull over unsolicited; thank them and tell them help is on the way.