I have always been leery about this. Probably not a big deal, but I was driving to work one day and saw a rig pulling a sled coming the opposite direction. The sled had the rods stored upright on the center console.

There were 4 rods all snapped in the exact same area, the driver didn't even know what happened. Don't know if he hit the height bar at McDonalds, or a branch smacked his rod, but he was headed for a bad morning.