There are maps that list bridge heights. To be safe, measure your truck and know your clearances. To my knowledge there are no GPS systems that warn you. Get out and look when in doubt. Use a spotter when possible, drop your air suspension if you can. Don't rely on someone on the sidewalk telling you, "yeah you'll fit, trucks go under that bridge all the time". I hate that one! Best of luck, and I quess you could always use a pole on your front bumper like the oversized loads escorts use? Just a thought!