yep it's normal, its a sensor, so if your going up or down the hill it will change slighty because your not on flat ground , you can go pretty far with the orange light coming on, i was on red light, and was on the motorway, but i managed to go below the bottom line and manage to get a good 20miles out of it, i was sooooooooooooo scared as i didnt mean to join the motorway that day.