Ability to find routes that avoid single lane two-way roads as much as possible

[simonw]

Parts of rural England such as Devon frequently have roads that are single lanes - such that two vehicles cannot pass each other - but allow traffic in both directions.

If you are driving down one of these and meet a vehicle traveling in the opposite direction one of you has to reverse until you reach a passing point.

This is very stressful! I would very much appreciate the option to avoid this kind of road where possible - I would rather add 10-15 minutes to my journey if it avoids this kind of road.

[simonw]

Here's a photo illustrating why these roads can be so stressful!

[biodranik]

Thanks! How are these roads mapped in OpenStreetMap.org ? How many of these roads are at taginfo?

[1ec5]

Taginfo reports about 8,600 instances of oneway=alternating, though more roads may just be tagged as lanes=1.5 or lanes=1 oneway=no. In particular, I suspect many alleys and driveways would have the same obstructions implicitly.

[simonw]

From https://wiki.openstreetmap.org/wiki/Key:lanes

Narrow roads

There exist roads with no marked lanes, which are two-way roads but without marked lanes and so narrow, that vehicles must slow down to pass each other. This can be tagged with narrow=yes.

[matkoniecz]

Note that oneway=alternating is for where one becomes oneway on and off.

lanes=1 roads are where it is not guided and what exactly happens is effectively negotiated between drivers.

[matkoniecz]

https://taginfo.openstreetmap.org/tags/lanes=1#combinations

3 970 835 lanes=1 on highway=

2 336 981 lanes=1 with oneway=yes

That leaves about 3 970 835-2 336 981=1 633 854 cases. Though we have that silly annoying idea of implied oneway roads...

So we may need to remove 351 578 highway=motorway_link 14 667 highway=motorway (how you get single lane motorway?) 148 363 junction=roundabout

1633854-351578-14667-148363=1119246

Note that say highway=motorway_link junction=roundabout lanes=1 oneway=yes would be removed multiple times, this value should be an underestimate.

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with over one million cases getting them at least some noticeable routing cost makes sense

[1ec5]

how you get single lane motorway?

Rarely, a dual carriageway can be one lane in either direction:

Possibly more commonly, a motorway may have one carriageway given over to HOVs as an express lane.

[matkoniecz]

Rarely, a dual carriageway can be one lane in either direction:

Oh definitely - though I was not aware that these could get classified as highway=motorway (this one has not got for example a proper median)