The Open Source Routing Machine is a great way to check consistency of tagging along a long stretches of continuous road. Mistakes in the tagging such as typos in names and refs appear as changes in the route, and it will also show where the tag change appears.
The ‘ref’ tag
OSRM uses the ref tag by preference to display the English language description of a route, e.g. “turn left onto CO 50”, so it makes a lot of sense to get the correct information here.
A ‘real world’ example
Passes & Canyons is a Colorado motorcycling website/blog. It offers information on day trips on both paved and unpaved roads. One of these is Cuchara, Colorado to Aguilar via Gulnare. Here is how the web site describes the route:
(Huerfano/USFS(San Isabel) #415,#416/Las Animas #48.0,#46.0,#43.7) Cuchara to Aguilar AKA Apishapa River Road, Cordova Pass – approximately 33 miles.
From Cuchara take CO 12 South past the ski area to the top of Cuchara Pass. Turn east on the dirt road (USFS 415, but may also have a Huerfano county number). This road changes number several times but if you stay on the main road at all intersections you should arrive in Aguilar.
Note how vague the description of the road numbers are.
By using OSRM to check the consistency of tags, here’s how the section of the route from Cucahara to Gulnare is described: A link to the route is Here
Distance: 51.2 km Duration: 1 h 3 min [Generate Link] [GPX File]
Head northeast onto 5th Avenue 24 m
Turn left onto City Avenue 53 m
Turn left onto CO 12 9.54 km
Turn left onto FR 415 / CR 364 9.99 km
Continue onto FR 415 / CR 46 8.63 km
Continue onto CR 46 18.9 km
Turn slight right onto (46) 4.13 km
As shown, using the ‘ref tag’ allows OSRM to offer a consistent naming scheme. The Forest Road number (415) stays the same, but the County Road number changes as the road crosses the County line from Huerfano to Las Animas County, then the FR number disappears as the road leaves the San Isabel National Forest. The (46) on the last section indicates an error that I have not yet corrected in the ‘ref’ tag for that section.
Incidentally, Google Maps can’t even map this route. It only offers the paved routes via La Veta or Trinidad