[ubernostrum]

If everyone followed the traffic rules instead of considering themselves smarter than traffic engineers

Traffic engineers don't set speed limits. Politicians do. If politicians would stop thinking they're smarter than the engineers, the speed limits would match the design and operating speeds of the roads much more often.

[TeMPOraL]

Politicians don't think they're smarter than engineers. They just do what politicians do. Pandering to the public and seeking easy revenue, the latter in this case is possible only because drivers are irresponsible and can be gamed for money by lowering speed limits. Anyway, I wouldn't accuse politicians of being any saner than your average driver when on the road.