[Tagging] gross weight - conclusions & changes

[martinq]

Based on the interesting discussion so far, following conclusions from 
my side:

(1) Remove the '_':
maxgross_weight was a horrible choice from my side. If we have 
'maxaxleload', then maxgrossweight is OK, but less irritating.

(2)
For consistency with (1), for the value in conditionals is also changed 
to 'grossweight' without '_', e.g. maxspeed:hgv = 80 @ (grossweight > 
7.5 AND 22:00-05:00)

(3) Don't touch 'maxweight' definition:
Since we must assume that 'maxweight' (100,000 uses!) was used for gross 
weight limits (e.g. signs with the lorry + weight) as well as for actual 
weight limits (e.g. signs with weight number only) in the past, any 
attempt to modify the tag retrospectively just causes chaos [the tag is 
somehow broken or at least very imprecise].

Only gradual replacement by new & more precise tags and the 
recommendation to use the new tags instead of the inaccurate 'maxweight' 
[deprecate maxweight] makes sense.

(4)
If definition of 'maxweight' is not changed [see (3)], we need a new tag 
for the "actual" weight.
I propose 'maxladenweight', because "laden weight" seems to be used at 
least in legal texts. Also acceptable could be "total weight".

(5) Vehicle, trailers and tractor+trailer(s) combinations:
Yet not properly considered in the RFC: Both weight limits (gross and 
laden) can apply to 'vehicles' (which is a trailer *or* the motor 
vehicle in front) or to 'combinations' of tractor+trailer(s).

Since they occur in all possible combinations in the real world, we need 
a tagging system for these 2x2 cases.

I am not sure how to address that, but instead of inventing a vehicle 
category combination system like maxladenweight:hgv+trailer or 
maxladenweight:combination, I tend to propose following solution:

maxladenweight/maxgrossweight: Limit for the the laden/gross weight of a 
vehicle, the vehicle can be restricted by adding an existing category, 
e.g. :hgv
maxladencombinationweight/maxgrosscombinationweight - limit for the 
laden weight of the vehicle *and all its trailers* (sum). The type of 
the tractor vehicle can be restricted by adding an existing category, 
e.g. :goods or :motorcar [The tags are too long? Yes! Give me alternatives!]

I somehow hate it to add this complexity, since casual mappers require 
deeper understanding about the different type of weight restrictions on 
road signs (which is by far not common knowledge) and their tagging 
differences. But if we want to have useful weight limit tags that make 
sense for potential HGV routing, the four cases needs to be covered.

And with a "road sign to mapping" table, at least for the most common 
road signs, it should be still feasible for casual mappers to map a 
weight restriction. The good thing is that most road signs still just 
require one tag.

(6) While the concept could be extended to even more weight related 
restrictions (e.g. maxcurbweight, maxdryweight), the RFC will not 
include them and will not be extended by me. I don't want to propose 
tags I am not going to use. They can be added by another proposal if 
somebody thinks they are important.

I will wait for responses if I understood the feedback right. After that 
I will rework the RFC.

martinq