[Talk-GB] trunk roads

[Richard Fairhurst]

Abigail Brady wrote:

> A table (badly spaced, I know, blame googlemail)
>
>   highway      colour      actual legal status of this colour
>
>   motorway     blue        motorway
>   trunk        green       primary route
>   primary      red         non-primary A-road
>   secondary    orange      B-road

Yay! Spot on!

Abigail gets the prize for having understood the bizarro OSM road  
classification in the shortest time yet. It took me about a year.

Steve:

> The Phillips map I have seems to show trunk roads the same as A  
> roads. We show them fundamentally different. Why is that?

We show primary differently to non-primary, just like the Philips map.  
The difference is that we call primary "trunk" and non-primary  
"primary". Yeah, I know.

(To be fair we're not a UK project so there's no reason why our tags  
should equate to UK classification.)

> Does the highways agency magically decide that they're 'trunk'

Yes.

> or do they have some fundamental real-world feature like more money  
> spent on them, more policing or anything like that?

More of the money spent on them comes from central govt.

> if there were a route that we knew was better... should we show what
> some government agency says is 'the route' or should we show another
> route as an 'A' road (eg deep red) to suggest to drivers that route
> if we know its better?
>
> I can't actually think of such a route for A roads or even B roads  
> but I assume they exist?

Easy one: Gloucester->Ross-on-Wye - the primary A40 sucks; the  
B4221-or-something through Newent, then the M50 for a couple of miles,  
is much better.

This one is probably dealt best through routing, like you say, and  
supplementary tags. If your road is well drawn (conveys bendiness) and  
tagged (conveys speed limits) then the routing algorithm will pick it  
up. Maybe hgv_use=heavy would also help the rest of us to avoid it. ;)

I'd love to see average_speed=n, derived from real-world GPS data as  
collected by OSM users.

cheers
Richard