The conventional wisdom is that established speed limits lead to an increase in safety.
Speed limits are usually set to attempt to cap road traffic speed; there are several reasons for wanting to do this. It is often done with an intention to improve road traffic safety and reduce the number of road traffic casualties from traffic collisions. In their World report on road traffic injury prevention report, the World Health Organization (WHO) identify speed control as one of various interventions likely to contribute to a reduction in road casualties.
Wikipedia: Speed Limit
I am inclined to question the conventional wisdom, especially when those proposing the restrictions have something to benefit by maintaining and enforcing restrictions (ticket revenues, enforcement disgression, etc).
To be clear, I am not talking about raising the speed limit. I think the presence of any established limit has a psychological effect on people, who may actually drive faster than is safe if a sign says that it is permissible. I am also not asking if driving a car too fast for conditions is dangerous, that seems pretty clear. I am asking if establishing and posting a legal speed limit decreases the danger on highways. I am also restricting this query to highways, since I believe that they are fundamentally different than surface and residential streets, and the data for each will be vastly different, so different conclusions may be reached.