Came across a reference to the fact that at one point the US state of Montana actually had no speed limits. After a search I came across this article outlining the accident rate during this period which makes for some interesting reading. For the lazy a quick summary of the effects of having no speed limits were found to be: 1. Fatal accident rates on these highways reached an all time low in modern times. 2. On 2 lane highways with no posted limits the frequency of multiple vehicle accidents dropped 5 percent. 3. Seat belt usage rose to 88% percent, with only a secondary enforcement law. 4. Posted limits and their enforcement, had either no or a negative effect on traffic safety. 5. As predicted by the engineering models, traffic speeds did not significantly change and remained consistent with other western states with like conditions. 6. The people of Montana and its visitors continued to drive at speeds they were comfortable with, which were often speeds lower than their counter parts on high density urban freeways* with low posted limits. 7. The theory behind posting speed limits on this classification of road is to reduce conflicts in traffic flow, thereby reducing accidents. The paradox is that the desired effect from posting speed limits was achieved by removing them. Also during this 6 year period, Montana's rural interstates daytime speeds (no speed limit) were consistently lower (on average 5-10 mph and more) than the speeds being reported on many sections of Southern California's 65 mph posted urban interstates. Makes you wonder just what effect the strict enforcement of arbitrary speed limits really has on road safety.