[Talk-GB] Channel Tunnel Routing

[Philip Barnes]

On Sun, 2012-09-09 at 17:11 +0100, Andrew M. Bishop wrote:
> 
> As the author of routing software (Routino) I have followed this
> discussion with interest.
Thanks, I have just downloaded the latest and am going to give it a go.
Will let you know how I get on.

> 
> Having route=train_shuttle on the railway line is the easiest
> solution, this then would match route=ferry.  Currently Routino
> recognises ways with route=ferry and replaces them in its internal
> model with highway=ferry.  The same could be done for
> route=train_shuttle if the tag is on the way just by modifying the
> tag transformation rules.
> 
> The problem with having the route in a relation is that every way with
> a railway tag needs to be stored until the relation has been processed
> and the properties from it transferred to the constituent ways.
> 
> At the moment Routino understands some relations; the simplest turn
> restrictions and walking / cycling routes which default to having
> higher routing preference than other non-route-relation highways.  In
> these cases the relations are assumed to apply to existing highways
> (ways with a highway tag) so there is no extra temporary data to
> store.
> 
> One potential problem that I can see is if a route=train_shuttle
> railway crosses a road at a level crossing it might appear that the
> car can join the railway.  Limiting the points where vehicles can join
> trains would seem to be necessary but difficult to include in the
> existing data model of a router since it introduces a new special
> case.  A new sort of turn restriction could be used that allows
> something to happen which is disallowed in all other cases that don't
> have the turn restriction.
> 
That probably explains why the Sylt Shuttle is mapped as a separate way,
following the railway but not connecting to other ways. There are
several level crossings on that line.

In the case of the Channel Tunnel there are no level crossings, at least
not with public roads. I did have a few problems with the service tunnel
however.

How the routing is achieved is probably not so important, it does not
matter beyond the aesthetic, that the routing follows the railway, just
that the satnav routes via the M20, leaves at the right junction and is
not constantly nagging with 'turn around when possible' as you are
driving through the terminal. 

Phil