Fixed speed limits represent the appropriate speed for average conditions. Dynamic speed limits, on the other hand, are limits that take account of the real time traffic, road and weather conditions. Dynamic limits can better reflect the safe speed. If, for example, 80 is a safe speed in average conditions, 90 km/h may still be safe in optimal conditions, whereas 60 may still be too high in very busy, or dark and slippery conditions. Dynamic limits are also expected to increase the credibility of the speed limit system in general.
A number of countries apply dynamic speed limits on their motorways, related to traffic flow or weather conditions. Increasing technological developments would allow for dynamic speed limits at other road types as well and eventually integrated into intelligent speed adaptation devices.