[Tagging] Road hierarchy

Michael Tsang miklcct at gmail.com
Wed Aug 7 03:39:29 UTC 2019

On Sunday, 04 August 2019 23:06:47 HKT Paul Allen wrote:
> On Sun, 4 Aug 2019 at 15:51, Florian Lohoff <f at zz.de> wrote:
> > Where do you take this assumption from? I have never heard before that
> > residential may not be used for through traffic?
> Many residential roads are cul-de-sacs.  Dead ends.  Not classed as through
> roads because
> they don't lead anywhere except the houses that are on them.  Others can be
> used as routes
> from A to B but there are other routes that are shorter/wider/faster or
> some combination of those.
> And then there are tertiary (or higher) roads which lead from A to B but
> which also have houses
> along them.
> A cul-de-sac, which many residential roads are, can never be used by
> through traffic.  Roads
> used by through traffic can have houses on them.  It is useful to make a
> distinction in a way
> that makes sense.

In Hong Kong, there are two major roads Pok Fu Lam Road (uphill, primary) and 
Victoria Road (downhill, secondary), which serve as major thoroughfare between 
districts, which the former has much higher importance. There are two roads 
connecting them in Pok Fu Lam, one is called Sassoon Road, and another is in 
form of Y-shape with a loop at the centre called Bisney Road / Consort Rise.

Sassoon Road is suitable for medium-sized vehicles to pass through and is the 
preferred road for traffic going up / down the hill, which is mapped as tertiary 
(because it isn't used for major traffic between districts, but mainly used for 
accessing local destinations inside Pok Fu Lam, we don't have an official system 
lower than trunk). There is a university along the road.

Bisney Road / Consort Rise passes through a quiet neighbourhood which is steep 
and curved, making it unsuitable for any medium / large vehicles to pass with 
a legal weight limit restricted to light vehicles. Therefore it is mapped as 
residential. The primary purpose of that road is to access the neighbourhood, 
however some vehicles (including myself) also use it as a thoroughfare on a 
light vehicle (especially a motorcycle) because it is shorter and has less 
traffic than Sassoon Road, even through the speed is much slower as the road is 
steep and curved.

The ability of through traffic passing a road does not depend on the 
classification. As long as it is the shortest / widest / fastest path 
connecting major roads, it will have through traffic even the driving experience 
is the same as driving into a cul-de-sac in a neighbourhood. Therefore we 
don't need to distinguish them in the tagging. The residential / unclassified 
difference should be reflected in the driving experience (you expect houses and 
residents on residential road which you should be careful not to disturb them, 
but not on an unclassified road).

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