Re-classifying service=alley and other narrow roads [Chiang Mai]

I’ve recently made some updates to narrow roads in Chiang Mai that were previously tagged as highway=service + service=alley, and some other misleading combinations including unsigned vehicle legal restrictions tags.

Based on the latest Wiki revisions, Mapillary, and local knowledge, I have re-classified them into more appropriate categories, such as:

  • Residential roads wide enough for a single motor car (at least 2 meters wide): highway=residential + lanes=1 + oneway=yes/no + surface=*
  • Roads too narrow for motorcars (less than 2 meters), and not restricted to motorcycles via signs/steps/barriers: highway=path + width=* + surface=*
  • Roads too narrow for motorcars (less than 2 meters), and restricted to motorcycles via signs/steps/barriers: highway=footway + width=* + surface=*

There are still many narrow roads and motorcycle paths in Chiang Mai and other provinces that have been incorrectly tagged as service=alley, highway=footway, and other different combinations. I encourage anyone who comes across these to update them accordingly based on the latest Thailand Wiki definitions.

If you’re unsure whether a very narrow road is passable by car, look for vehicles inside adjacent house driveways. If at least one car is parked inside, it means a section of the road is passable.

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I used to use this techniques too.

Cheers

I recently reclassified dozen more narrow roads in Chiang Mai that were still inconsistently (re)tagged as either service=alley or using a variation of motor_vehicle=Motorbike-Yes/Motorcar-No and motorcar=no + motorcycle=yes

As per our current Thailand wiki documentation, I’d like to highlight the following points:

  • It’s generally considered inappropriate to include motorcar=no or motor_vehicle=no on narrow roads without specific signage or obstacles.
  • Specifying motorcycle=yes is unnecessary since motorcycles are inherently allowed on highway=path by default (refer to OSM tags for routing/Access restrictions - OpenStreetMap Wiki).
  • Unnecessary legal access tags are hard to maintain and understand for new mappers, and may lead to more misinterpretations.
  • The tag service=alley should not be applied to narrow roads providing access to the front entrances of residences or shops.
  • To indicate that a road is too narrow for a car but accessible to motorcycles, the recommended tags are highway=path + width=X (where X usually less than 2 meters).
  • Determining the passability of certain narrow roads can be challenging; a simple method is to check for the presence of cars in nearby driveways, which are often present.
  • Including the width tag is crucial to maintain consistency and prevent fluctuations in highway tags. It should be added whenever the width is roughly known (one can add source:width=estimated)

These guidelines are not specific to Thailand but align with global wiki standards. Happy to revisit these discussions if you have a compelling argument for a Thailand-specific narrow road rule. Here are the relevant threads:

@Saikat_Maiti, I have exchanged before with a few of your Grab mappers, but still spotting some inconsistencies in how they map narrow roads. Any thoughts on this tagging approach? Could it possibly clash with Grab’s routing capabilities?

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Adding some visuals here for your reference:



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