If you restrict the basis of decision-making to certainty rather than "estimated likelihood", you would have to throw out pretty much everything mankind has ever learned using the scientific method (where evidence can support, or inrease the likelihood of a theory, but never prove it).
For example, the link between smoking and lung cancer. It's impossible to say of any specific case of lung cancer that it was definitely caused by smoking, but there is enough evidence for increased risk, so that deciding to quit based only on a likelihood is a reasonable thing to do.
>the legislator who drafts the speeding laws and the bureaucrat who sets the speed limits for particular roads can't possibly know as much as the driver
In the case of speed traps, that's irrelevant; the limits there are not abnormally low because the legislators and bureaucrats are using unsound information, but because they intentionally ignore (or don't even bother acquiring) recommendations which indicate that a higher speed would be safe.