[Talk-GB] Cycle lane in one direction only

[Dave Stubbs]

On Tue, Sep 30, 2008 at 7:29 PM, Gregory Williams
<gregory.williams at purplegeodesoftware.co.uk> wrote:
>> -----Original Message-----
>> From: talk-gb-bounces at openstreetmap.org [mailto:talk-gb-
>> bounces at openstreetmap.org] On Behalf Of LeedsTracker
>> Sent: 30 September 2008 18:49
>> To: talk-gb at openstreetmap.org
>> Subject: Re: [Talk-GB] Cycle lane in one direction only
>>
>> 2008/9/30 Andrew Chadwick (mailing lists) <andrewc-email-
>> lists at piffle.org>:
>>
>> > Suggestions of different things to use in place of :left and :right
>> > would be very welcome. I'd suggest keeping it defined in terms that
>> > allow rendering without foreknowledge of which side of the road one
>> > cycles/drives in a particular country.
>>
>> Can't we use the direction of the way being tagged? E.g.
>> cycleway:withway=<any permissible value for cycleway>
>> cycleway:againstway=<any permissible value for cycleway>
>>
>> If neither withway/againstway are given, assume both ways as default
>
> If you did that then you'd need to know which side of the road you cycle
> on in order to be able to render a lane on the correct side.
>

There are cases you have to know whichever scheme you use. Left/right
works for renderers, but is no use for routers, and forward/backward
works for routers, but not for renderers.
Luckily figuring out what the general rule of the road is probably
isn't /that/ hard. There are a limited number of countries that drive
on the left and most of them are islands making the bounding box easy,
and the biggest land borders are pretty much India+Pakistan and
southern Africa (both of which are comparitively sparse border areas,
unlikely to be too obsessed with cycle facilities). At least that's
the situation wikipedia implies [1], so it must be true :-)

Dave

[1] http://en.wikipedia.org/wiki/Drive_on_the_left