I only saw slow busses going under the speed limit, and cars trying to overtake out of frustration. Excessive speed wasn't something that I observed. Apparently there are speed cameras in the tunnel, normally there's a sign a few hundred metres ahead of each camera warning you of their presence but I didn't see any such signs in the tunnel, or cameras. In Norway I generally find that I'm the slowest person on the road. They are very low speed limits compared to other countries. Despite the threat of needing to take out a 2nd mortgage to pay a speeding fine, it doesn't seem to deter Norwegians at first glance, but they do have lower road fatalities compared to Scotland despite more hazardous roads and similar populations.