Speed kills. Or so the advertisements tell us, and so we have speed limits to reduce the number of injuries and fatalities. But there are cases where these very limits act to our detriment.
In general, any arbitrary fixed limit inhibits the optimal functioning of a system. I’m not against speed limits per se; they provide a useful limitation that manages our tendency to discount low frequency high consequence events. Being required to travel at a speed noticeably slower than the conditions and road allow results in either frustration, or more insidiously, boredom.
The two main areas I find this situation are empty roads and open roads. The first suffers from the fact that our speed limits are fixed, and are set for normal traveling conditions. The second suffers because we have an arbitrary maximum on speed limits of 110km/h.
Ever driven on a major urban road late at night? Normally packed lanes are empty, and because the roads are so well constructed to deal with peak flows during the day, the natural speed you would drive at sans speed limit is rather higher than the fixed limit that serves just fine during the day. Nominally I would think most 70kmh roads (as these roads typically are) could easily be rated at 90 overnight.
Open country roads and highways have a different issue. Here you have a case where our arbitrary limit increases the likelihood of having an accident. This accrues through two sources. Firstly trips take longer than they should, leading to increased fatigue. Secondly, traveling at a speed appropriate to the conditions keeps you focussed on the task; it keeps driving an active role. Here, speed limits act to decrease your attention and restrict you to a speed where so little input is required that staying awake rapidly becomes difficult.
Speed limits are good. Arbitrary limits on what those can be are not. At best, speed limits that are poorly related to current conditions are frustrating; at worst they are fatal. Slower is not always safer and this needs to be recognized.