Because most citizens can be relied upon to behave in a reasonable manner as they go about their daily activities, many of laws reflect observations of the way reasonable people behave under most circumstances. Traffic regulations are invariably based upon observations of the behavior of groups of travelers under various conditions.
Generally speaking, traffic laws that reflect the behavior of the majority of vehicle operators are found to be successful, while laws that arbitrarily restrict the majority of drivers encourage violations, lack public support and usually fail to bring about desirable changes in driving behavior. These effects are especially true of speed zoning.
Speed zoning is based upon several fundamental concepts deeply rooted in the American system of government and law.
- Driving behavior is an extension of social attitude, and the majority of drivers respond in a safe and reasonable manner as demonstrated by their consistently favorable driving records.
- The normally careful and competent actions of a reasonable person should be considered legal.
- Laws are established for the protection of the public and the regulation of unreasonable behavior on the part of individuals.
- Laws cannot be effectively enforced without the consent and voluntary compliance of the public majority.
Public acceptance of these concepts is normally instinctive. However, the same public, when emotionally aroused in a specific instance, will often reject these fundamentals and rely instead on more comfortable and widely held misconceptions:
- Speed limit signs slow the speed of traffic.
- Speed limit signs decrease the crash rate and increase safety.
- Raising a posted speed limit causes an increase in the speed of traffic.
- Any posted speed limit must be safer than an unposted speed limit, regardless of the traffic and roadway conditions prevailing.
"Before and after" studies consistently demonstrate that there are no significant changes in traffic speeds following the posting of new or revised speed limits. Furthermore, no published research findings have established any direct relationship between posted speed limits and crash frequency, but short-term reductions have resulted from saturation enforcement efforts directed at speed and other traffic-law violations.
Police agencies necessarily rely on reasonable and well-recognized speed laws to control the unreasonable violators whose behavior is clearly out of line with the normal flow of traffic.
Contrary to popular belief, speed in itself is not a major cause of crashes. In fact, there is a consensus of professional opinions that many speed-related crashes result from both excessively low and high speeds.
It is accepted within the traffic-engineering profession that there is a demonstrated need to produce as much uniformity as possible in the traffic flow and to eliminate the so-called speed trap. A speed trap may be defined as a street or road that is wide enough, straight and smooth enough, and sufficiently free of visibility-limiting obstructions to permit driving a certain speed, but where the law nevertheless calls for a much lower speed.