[Tagging] maxspeed=signals

[Martin Vonwald]

2012/6/26 Peter Wendorff <wendorff at uni-paderborn.de>:
> I would prefer to allow (not require) an additional unit information (mph,
> km/h)

Sorry - my writing was misleading. Of course the unit should be allowed!


>> * A different tag should be used if the speed limit is somehow
>> managed, maybe maxspeed:managed=yes or something similar.
>>
>> Why do I think that maxspeed=signals is a bad idea? Because it doesn't
>> carry a lot of useful information. The speed limit is especially
>> important to routing applications. For such an application
>> maxspeed=signals is no information at all and it might fall back to
>> the country-specific default limit - and this may (and will quite
>> often) be wrong.
>
> But what is NOT wrong?
> maxspeed is the maximum allowed speed limit.
> If there's a signal controlled, variable maxspeed limit, this is usually
> lower than the national default, as it's used to calm down traffic in rush
> hours and whenever it get's dangerous to drive fast.
> Therefore I don't know any of these controls, that usually shows higher
> maxspeeds than the default.
> It follows, that such a fallback is definitively not wrong.

On the S6 in Austria many (electronic) speed signs show 100, except in
case of bad weather or accidents. The national default would be 130.
If we provide those 100 as maxspeed, routing could be more precise. If
we provide maxspeed=signals, routing would be done with 130 and this -
in this case - is clearly wrong. Of course the speed limit might be
even lower, but under normal circumstances(!) the speed limit would be
100.


> What is "the usual" traffic?
> In Germany the ones I know often are "unlimited" - meaning national default
> - at night (between 23:00 and 5:00 a.m for example), where there's not much
> traffic, and sometimes 30km/h during rush hours.
> So what do you want to put in here?
> The national default? well, that's possible with the current scheme. It's
> the fastest possible useful estimation, and most likely not a very good
> guess.
> Adding a maxspeed=70, because that's what YOU usually see there, driving
> along everytime e.g. at 13:00, outside the rush hour?
> Adding a maxpeed=5, because you're someone driving along in the rush hours
> every day?

Do the signs really show 5?

> Nothing is a good guess for everybody, and I don't think a time schedule for
> USUAL speed limits is a giood idea.

I was mainly talking about the example I provided above. There's no
guessing, estimating and also no time schedule.

Martin