Speed signs should be removed from most urban roads. They are not necessary in most places, hazardous on the roadside, waste tonnes of steel and distract drivers from their main task.
The design of speed signage is arranged to prove you wrong not help you get it right. There is a better, safer and more environmentally-friendly way. The explanation is about the difference between discrete information and continuous information.
Signs are discrete; meaning you see them every now and then along the roadway. There will be one at the change of limit zone and then every so often within the zone. wherever you are there is a limit. You might not be able to see the sign but it can be proved what limit applies by reference to a sign further back on the road. Thus the signs can prove why you have done something wrong but they are not well designed in terms of helping people to get it right. The problem is that at any given moment you can not necessarily see what speed limit applies. So you either:
(a) drive at the default (50km/hr in urban areas in Victoria, Australia); or
(b) guess; or
(c) go with the traffic; and
(d) all the time be distracted from the main task by looking for signs.
If you do (a) you risk going far too slow compared to other people thus increasing overtaking movements and be subjected to tailgating, road rage, etc. If you do (b) or (c) you will get fined if you are ultimately wrong. All of these involve looking around for signs and thus less concentration on the road ahead, checking mirrors, etc. That is why the system of signage – when coupled with strict enforcement – has an element of danger in its design.
A better way is easy, free and provides continues information – next post.