[Tagging] Feature proposal - RFC - gross weight

[martinq]

Restrictions on road access in many countries of the world make use of 
two different types of weight:

1) Actual weight of vehicle including empty vehicle + driver + 
passengers + load [the weight on a weighbridge]

2) Maximum permissible weight for a vehicle, typically used for 
registration and found in vehicle documents [and is a fixed number for a 
specific vehicle, not depending on the load]


But current tagging does not distinguish the two types, neither 
maxweight=x nor access:conditional=... @ (weight>x).

But the difference is important for HGV routing and truck drivers and 
should be tagged more precisely.

Since most car driver [and thus the average mapper] typically don't have 
to care & know details about weight restrictions, I assume that many 
mappers are not aware of the subtle difference in the meaning of weight 
related road signs [at least I haven't until I investigated the 
situation]. Thus I decided to summarize previous discussions and my 
knowledge in following proposal:

http://wiki.openstreetmap.org/wiki/Proposed_features/gross_weight

I have added many examples to illustrate when road signs mean "gross 
weight" and when the refer to the actual weight.

To avoid a German/Austrian bias I based many examples on the Vienna 
Convention on road signs and signals, which has been implemented in many 
countries in the world (this convention is the reasons why road signs 
look very similar in many countries).

I know that some countries have not fully implemented this convention 
and thus there a country specific deviations, thus please update the 
comment column of the example if your country deviates from the 
convention rules.

martinq