Thus, there is a necessity to be able to distinguish roads designated as autoroutes from other national highways. Whether a highway is an autoroute or not, cannot be linked to physical properties of the road (e.g. dual carriageway / all roads tagged as highway=motorway), at least not by law, because
In other words, the law does not dictate any hard requirements for a highway to be designated as an autoroute. How it looks in the reality I do not know, but not sure if it is relevant unless the situation is absolutely unambiguous.
So, my question: Is it possible to determine whether a highway is an autoroute based on the tags of that highway? Are all autoroutes consistently tagged in a way so that they can be clearly distinguished from other highway?
And, well, if not, what’s your suggestion for a tag that denotes this?
This might be influenced by the broader Canadian practice of simply referring to highways by number alone (e.g., “Highway 401”). I’m unsure if there’s a strong reason for Québec routes to follow that convention, since there is a consistent alphanumeric abbreviation scheme. Regardless, you can unambiguously identify a motorway as carrying a Québec autoroute by its membership in a route relation tagged network=CA:QC:A.
There’s a very simple reason that the ref tagging on Quebec highways doesn’t use “A-__” prefixes: by definition all provincial highways numbered 1-99 and 400-999 are autoroutes. The numbering doesn’t overlap with other classifications of provincial highways, so you don’t need to disambiguate any further. It’s not like in the US where you might have “Interstate ##”, “US Route ##” and “State Route ##” all in the same state, or “Autobahn ##” and “Bundestraße ##” in Germany. (Keep in mind there is no overarching federal highway system or standard in Canada.) A Quebec highway with ref=20 for example is, by definition, an autoroute; a Quebec highway ref=234 is by definition a lower-tiered ‘route’.
Yes, since @westnordost’s default speed limits parser necessarily varies rules by jurisdiction, this heuristic should be workable. For completeness, note that the forest routes are being tagged with alphanumeric way refs to avoid conflicting with the autoroute numbering scheme, for example ref=R0404, corresponding to what’s signposted as “R 404” on a blue shield. (There are also route relations tagged with network=CA:QC:R, but not as comprehensively as for autoroutes.)
Yes, the forestry roads are tagged ref=R####, as the respective blue shield signs do read “R ####”. (Whereas the routes and autoroutes just have a numbered shield with no ‘A’ or ‘R’.) Note also that the forestry roads are now four digits, which may or may not be reflected in posted signage, but there is a method to the madness in that the first two digits in the four-digit code correspond with the administrative region the road is located in. E.g. all forestry roads that begin with ‘04’ are in Mauricie.
Oh well, nevermind. It is, and you also provided a link earlier:
Motorway: autoroutes, including the two-lane ways where you can drive 100, and spur roads with 4xx, 5xx, 6xx or 9xx designations;
Trunk: autoroute part of National Highway Service (federal) (NHS) that is not dual carriageway (ie: double central yellow line and not separated by grass). Good example is the autoroute 50 between Lachute and Gatineau as well as the 117 up to Ontario border.
Some trunk roads are on autoroutes, such as the Route de la Bravoure. My impression is that Québec is more or less using a mix of connectivity- and designation-based definitions of highway=trunk. The definition posted above incorporates the National Highway Service System. This is often tagged with NHS, but I don’t know if it’s consistent enough to use in your software.
In fact, the word autoroute can appear in the name of a road that isn’t designated as an autoroute, as the French translation of the English word “expressway”, for example in Route 136 (Autoroute Ville-Marie). This leads me to wonder if the law you cited applies to anything that is built as an freeway/expressway or anything that is designated as an autoroute.
The latter is a very, very, very specific edge case, in that Autoroute René-Levesque is co-signed as Autoroute 20 north of the Champlain Bridge and Autoroute 15 south of the bridge, but the segment between the on/off-ramps to/from the bridge is technically part of neither autoroute.