maxspeed:practical

[d1g]

Some of us would appreciate hints about practical/physical max speed.

• Not always dangerous/curved roads marked with max speed signs
• over-parked roads (illegally or not)
• we cannot truly deduce value of "surface=unpaved + note=horrible road" unlike number (25,30)

It was created in Russian community first with 442-message long discussion about it and when/why to use it

In April'16 it was extended with methology how to enter values

Using "debug" layer of OSRM I was able to find roads with 40-56 km/h "defaults" where in the real world you won't able to travel faster than 20-30. I know that there many places in the world where you can never drive faster than (number known to locals). Using this value wisely would improve routing results without drawbacks.

This tag was supported for years now, thanks to @liosha and his osm2mp 1 2

[d1g]

As was pointed by Marek kleciak and Alv, not all of deprecation arguments make sense:

Some of them are pure "bad faith assumptions": "Absolutely pointless. Every mapper would tag this different".

We made precise description why and how to evaluate and tag maxspeed:practical in Russian, please use it, translate it and tag it :)

[d1g]

My suggestion is to evaluate weather condition and other coefficients after base cost of maxspeed:practical.

It was never claimed that maxspeed:practical is about wet/weather conditions.

BTW maxspeed:practical may be evaluated slightly beyond single segment, because you should drop speed before this segment (and gain speed back after leaving this segment).

[TheMarex]

We are not going to support maxspeed:practical in the default profile. It is a subjectve value. For getting precise ETAs there is no way around integrating real world measured average speeds for every road (or rather learn real speed models depending on the time for each road). This can be achieved by GPS probe data. Projects like https://github.com/opentraffic try to make data like this accessible to the general public and sure could need some additional support.

Using a single value to give practical speed is rather futile and I would not waste a huge effort in adding support for this.