[Talk-us] Ferries

Martijn van Exel martijnv at telenav.com
Thu Oct 17 03:38:03 UTC 2013

We just had an interesting discussion about ferry routing here at Telenav.

In our testing we see that we sometimes fail to route folks over car
ferries, even if that would be the preferred route and alternatives
would be much, much longer.

It turns out that this happens because some of the access roads to
these ferries are tagged as highway=service, sometimes
service=driveway. For various reasons we don't want to route folks
through service roads, so this poses a challenge. Here's an example:

As a lightweight solution, we came up with this idea: why don't we tag
service roads that lead to and from a ferry as access=ferry. The
access= qualifier is already common on service roads, because of the
nature of highway=service as a road that generally provides access to
some particular destination.

This is not going to be affecting a huge number of ways - there are
only around 500 or so ways tagged with route=ferry, of those, only a
minority are car ferries, and of those, only a small amount would have
only service roads connected to them. I can figure out how many
exactly if you're interested.

I am curious to hear your thoughts.

Martijn van Exel
OSM data specialist

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