[OSM-talk] dangerous cycling lanes (was Re: A new highwaytaggingscheme-thinking about)

Ian Sergeant isergean at hih.com.au
Thu Aug 30 23:50:54 BST 2007


Yesterday, I wrote:

> We need to capture things that make cycling good or bad on a route.  We
> need to capture the elements of what makes a good cycling route, traffic
> volumes, rough surfaces, high pedestrian volumes on paths, squeeze
points,
> inclines, propensity for debris, lighting, speed limits, etc, rather than
> an subjective assessment.

David Earl <david at frankieandshadow.com> wrote on 30/08/2007 07:43:05 PM:

> The key point is that a single (substantially objective) parameter is
> sufficient to provide a highly effective route plan. There aren't any
> significant hills in Cambridge though.

I'm all for the substantially objective - and against a classifications
like "good", "poor", "dangerous" etc.

A few local examples..

In NSW cycling on the shoulder of motorways is encouraged.  The freeway
heading south from Sydney is 110km/h freeway, with a couple of reasonably
serious hills, the propensity for debris on the shoulder, and no lighting.
As a cyclist, what do I want to see on a map?  At least that is is fast
road, with high traffic volumes, but segregated cycle facilities with no
obstructions.  On a scale of "good", "poor" etc, how would it rate?  I
really don't know.  Good, because there are segregated facilities?  Bad,
because of the debris?  Bad, because falling of your bike into the traffic
lane means certain death?  Bad because it is steep in parts?  Good because
it is considerably less steep than the alternative route through the park?

To cycle from my house to the station there are two ways to cycle.  Walk
your bike over the railway footbridge, or cycle a 75 meter uphill stretch
with a squeeze, which can be stressful with the traffic volume and no
overtaking space. As a cyclist, I'd like to know about the footbridge where
I can walk my bike.  I'd like to know about the uphill stretch, and
particularly that it is a squeeze point.  How would my footbridge rate?
Bad, because there are barriers which stop you just cycling across it?
Good, because it offers an alternative to the uphill squeeze?  How would
the other route rate?  Good, because you don't have to get off your bike?

I can see the argument for a single classification of a cycleway for
simplicity, and for routing.  However there are several bits of information
encoded within this single tag.  It is is likely other classifications will
be needed to incorporate other cities and various forms of cycling
facilities, and I single tag would end up with lots of combinations
encoding within it by the time we have encoded all the cycleway types on
the planet.  Just encoding incline will double the number classifications!

I appreciate the simplicity of the Cambridge system, and admire the fact
that they have something up and running, while I am still writing emails on
the subject.  However, I believe our job as OSM mappers should be true to
mapping what objectively exists, and leave it to the renderers and routers
to interpret the data for the benefit of their community.

Ian.





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