[OSM-talk] Highway=trunk : harmonization between countries ?

[john whelan]

>A typical city road posted 30 mph might move at 35 mph,

As someone who lives in a city street with one school in the middle and one
at either end posted at 40 km/h with an average traffic speed of 60 km/h
and over 100 km/h from some high school kids driving to and from school I
would prefer it if traffic stuck to the posted speed limits.  Cars running
across front lawns to avoid collisions are not unknown.

Cheerio John

On 22 Aug 2017 7:23 pm, "Greg Troxel" <gdt at lexort.com> wrote:

>
> Richard <ricoz.osm at gmail.com> writes:
>
> > On Tue, Aug 22, 2017 at 10:00:07PM +0200, Martin Koppenhoefer wrote:
> >>
> >>
> >> sent from a phone
> >>
> >> > On 22. Aug 2017, at 15:46, Richard <ricoz.osm at gmail.com> wrote:
> >> >
> >> > called differently, but this is it:
> >> > https://wiki.openstreetmap.org/wiki/Key:maxspeed:practical
> >>
> >>
> >> yes, but practical maxspeed depends a lot on your equipment and
> >> capabilities, and on other people driving in front of you, so this
> >> tag will probably not be very uniform around the globe. Also, some
> >> people are willing to risk a speeding ticket, others don't. With
> >> regard to the latter, the situation in Italy is particularly
> >> ridiculous: the authorities have to sign post speed controls ;-)
> >> i.e. speeding tickets are kind of rare.
>
> In most US states, there's a de facto limit higher than the signed limit
> where there is very little risk of a ticket.  I'm thinking that
> maxspeed:practical should be the 50th percentile of typical time actual
> speeds.
>
> > maxspeed:practical should take dense account or traffic jams into
> > account as good as possible. So far I am not aware of any router
> > evaluating time based conditional restrictions but those could be
> > used to take rush hours somewhat into account.
>
> Agreed.  Or even live traffic.  But I agree with the notion that
> maxspeed:practical should be a representative speed that's valid most of
> the time.
>
> > maxspeed:practical should not have any values above the legal speed
> > limit.. and if it had routers should ignore such values anyway, at
> > least thats what I would expect from navigation software.
> > Many years ago something like this was encouraged in the ancient
> > proposal but it is no longer in the description.. if there is any
> > remaining doubt I would explicitly state it in the wiki.
>
> This seems unreasonable.  Maybe where you are people follow speed limits
> (because they are enforced, or because speed limits are set by good
> engineering practice instead of arbitrarily).  In that case, though,
> maxspeed:practical will be essentially maxspeed anyway, and that's fine.
> But in Massachusetts, uncongested traffic in clear weather essentially
> always travels above the speed limit, and the delta varies by road type.
> A typical city road posted 30 mph might move at 35 mph, and an
> Interstate posted 65 mph might move at 80 mph.  But a particular road
> that's almost Interstate (and correctly tagged trunk!) that is
> inexplicably posted at 45 mph moves at 75 mph, because that's what all
> the drivers think is the safe speed.
>
> A router should be answering the question "If I take this route, what
> will happen" as accurately as possible, as a first step in choosing a
> route with a pleasing outcome.  Refusing to use a reasonable estimate of
> traffic flow because it's below an arbitrary, known not to be enforced
> limit, does users of the routing service a disservice.
>
> (I don't know what Apple maps does, but I think they use speed estimates
> from other apple users and do not clamp them to speed limits.  At least
> it seems that way in that Apple computes routes that are in fact fast
> but would be slower if speed limits were observed.)
>
> Computing a route based on what's known to happen is not the same thing
> as encouraging speeding -- it's more like admitting that it usually
> happens.  And in all cases the driver is deciding how to drive.
>
> So:
>
>   maxspeed:practical should be able to have higher values than maxspeed
>
>   routers should use those values, higher or not
>
> and if that's not ok, then we need
>
>   maxspeed:typical
>
> which is defined to be what usually happens, regardless of what anybody
> thinks about it.
>
> Greg
>
>
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