Without doubt, the laws that drivers fail to follow the most often must regard the speed limit. Everyone has a justification for doing so. They range from being in a hurry, which is selfish, to the limit is set too low which is either a reasonable observation or a result of failing to take all factors into consideration.
In the past, speeds were set according to engineering design standards. This was often varied by the 85th percentile rule. The logic behind this was that the limit was most likely to be followed if it was set at what the majority of drivers chose.
More recently, collision data was introduced to the equation. A higher incidence of collisions called for a reduction in the speed limit. This will likely be supplanted by tending toward speeds that will mean road users will survive and injury will be minimized if a collision does occur.
What does the future hold? Perhaps we will factor in the production of greenhouse gases. Fuel consumption rises rapidly with speed and this is directly related to what comes out of the tailpipe.
Obviously, setting a credible speed limit that drivers will accept and follow is a difficult task. However, if it is accomplished there will be a high degree of voluntary compliance and perhaps a safer driving environment.