Re: speeding fines
But that's just it, the speed you can go on a particular bit of road is already variable. The posted limit, which used to be set at the 95th percentile of best case, is the _maximum_.
If it is rainy, or foggy, or kicking out time at the school, you probably should not be at say the 50 limit that stretch of road otherwise warrants. Unfortunately there are many retards and unobservant drivers around who can't or won't drive to the conditions. This leads to situations where we have limits being artificially reduced on broad swathes of road, just to cope with one slightly tight bend near one end, and ultimately to generally slower and slower limits being imposed.
This in turn leads to devaluing the lower limits, driver resentment of said low speed limits, and then more 'speeding' because people drive to the perceived risk of the bit of road they are on.
The better action is to engineer that bit of road so that the speed the majority of people would drive below is safe rather than attempt to force lower limits. If you want engage drivers in slowing themselves down, you need to have road engineers redesign the road so drivers believe it to be riskier. For instance, planting trees down the edge of the road leads to a significant decrease in driver speeds, as do things like pedestrian refuges in the centre of the road.