Sorry, I should specified which kinds of designations I speak of, like NHS (National Highway System) designations. These for example are the highways that the FHWA has deemed the most important to the country logistically, usually those that links major industrial and/or transport hubs. Sometimes, however, a highway number designation can be relevant to the road's importance, like an Interstate or U.S. Route, and even state routes in some states or in rural areas of a state like Nevada, but not always. Highway numbers can and should be taken into consideration on a case-by-case basis but in urban areas like Las Vegas than can almost always be ignored since they're more relics of the past and now only reflect who maintains the road rather than how important it is or a sign to be used for navigation.

I would say that it may not be that necessary to make a list of state highways in Nevada, as Wikipedia's list can be used if needed—but if you were to go about creating a proposal for the community, you can create a page on the OSM Wiki.

In short—the community and your own personal judgement.

The rules are really just vague guidelines that are followed by local OSM communities or individuals who try to put two-and-two together based off how everyone else does it. For US road classification specifically, these are based upon a community-built, consensus-approved documentation like this OSM Wiki page: osm.wiki/United_States/2021_Highway_Classification_Guidance

For primary roads in urban areas in particular, the guidelines would be to use this classification on the most important arterial roads—which is vague, and up to interpretation. Prior to when I started editing, a lot of the Las Vegas Valley's primary roads already followed this guideline. If I can recall correctly, the original significant primary roads in the valley were Craig, Lake Mead, Charleston, Tropicana, Boulder Highway, Las Vegas Blvd, Rainbow, Rancho, Paradise, Eastern, 5th Street, and Nellis—some of the most important arterial roads in the area at a glance. I went off how these were classified and upgraded other secondary roads, like Durango, Sahara, Cheyenne, etc. up to primary based on their similar roles and characteristics (like connectivity with major highways and regions of the valley, AADT, physical construction, road designation, HGV route) etc.

Unfortunately, a lot of highway classification cannot be determined with a source or a road number, and it will have to be up to the opinions of one, two, or many mappers. This can be avoided with a state highway classification page, but as far as I know, Nevada doesn't have one (yet). For the mean time, discussing and scrutinizing each road with other mappers one-by-one may be the best way to go about it.

It might be better to keep 5th Street primary here despite its relatively low AADT (when compared to east-wets routes—it still is the highest traffic north-south route through here), it actually is a very high-connectivity thoroughfare on the basis that it is the most direct north-south route through suburban North Las Vegas, linking the area to Downtown Las Vegas in a straight shot—plus it has connections with the Beltway in the north and I 15 via Cheyenne or Lake Mead in the south. I would wager that these are some of the reasons why the Federal Highway Administration even designated this as an NHS route.

You are correct in that it is useful for serving as a "do not re-map" note for users, which is harmless, but in an area like a construction site—and area that is subject to frequent updates—adding extra nodes, ways, and area polygons creates more clutter to have to work with and try to not to break as you add new features to the area or update their alignments to match imagery, etc.

Some people will be in favor of mapping demolished features to leave a note, while some will be wholly against adding more non-rendering clutter to the map, though, in my opinion, it should be fine as long as it can't be assumed at first glance that the road no longer exists, like in a situation where there isn't an under-construction roadway mapped right over its old alignment, in which case I would just add a note to the way.

Alta seems good as-is as well. While a freeway connection is a plus for justifying upgrading a road from tertiary to secondary, it's not necessarily required for secondary classification. Alta in its own merits should qualify for being a secondary road in that it provides a single straight shot route from Summerlin West to Downtown. And with its physical construction and AADT, it also slots right between a typical grid collector road you would see tagged as tertiary and a major primary thoroughfare like Charleston. Summerlin West may not be the perfect contender for a primary route (at least for the time being, over the coming years when it gets more built-up that could change), but it's still a major neighborhood seeing more and more traffic using these arterial roads by the day as it continues to grow.

Secondary would probably be the best classification for this section, especially since this forms a straight shot connection between Charleston, Town Center, and the Beltway when it transitions to Far Hills Avenue. It does have an AADT of 10k which is low compared to most other secondary roads in the valley, but not for the Summerlin area, since Alta and Anasazi see lower traffic counts themselves. Tertiary is best for smaller roads which see much less through traffic and connections to major roads, like Canyon Run Drive, Crestdale Lane, and Pavilion Center Drive.

Not necessarily, trunk roads are just major regional highways that could be any sort of road, divided or undivided, low or high speed, access-controlled or littered with driveways and adjacent properties. This is an example of a trunk road that happens to be an expressway. Historically, it may have been tagged as trunk for its physical construction as an expressway, but since the definition shifted from expressway to major inter-regional highways, it being a route linking the valley to Pahrump would be the reason for its trunk classification rather than because of it being a high-speed divided highway.

Blue Diamond Road does have driveway access, but its access is controlled by a central median and only accessible from the other side of the road via U-turn slip lanes in the median or at signalized intersections, rather than frequent median breaks or a central turn lane. While it's not fully-controlled access, the road is designed to handle large amount of traffic at highway speeds as opposed to the typical arterial like Rainbow which has far more driveway/side street access and lower speeds.

The section tagged as primary is where the I 15 ramps meet Spring Mountain leading traffic to Las Vegas Boulevard. West of the WB Spring Mountain to SB I 15 ramp and the ramps linking I 15 to EB Spring Mountain isn't being used by the same traffic getting between the Interstate and the Strip and effectively creates a short inaccessible primary stub being used only by traffic coming from the secondary route.

Wikipedia does have an article on collector roads—when referring to the street type (https://en.wikipedia.org/wiki/Collector_road) and an article about the local/express highway configuration, which does cover collector/distributor lanes within it (https://en.wikipedia.org/wiki/Local%E2%80%93express_lanes) (note that information won't be 1:1 with OSM classification criteria, but the info should be enough to give a general idea).

The best way of identifying these kinds of roads would probably be just through personal judgement. A narrower frontage-road like roadway that parallels the mainline freeway and links close-together interchanges to the main carriageways of the freeway can be assumed to be a collector-distributor lane and thus a type of long exit ramp rather than a separate freeway or a traditional frontage road.

The alternative would be to check official government maps. Not the TIGER-sourced background layers used you may find in an ArcGIS map, but a source that manually adds the roads like the CC OpenWeb, which labels these sort of roads as ramps in the Assessor Map layer.

I think this is the conflation of two different types of roads with different purposes that simply share the same name. The most common use for "collector road" refers to the bulk of the streets tagged as tertiary in the Las Vegas Valley. The other use of "collector road" applicable to these sort of ramps would be a more informal term for collector-distributor lanes, which do not serve as busier streets that traffic uses to get from local residential streets to the larger arterial roads, but rather are to separate traffic from the mainline highway between close-by interchanges, collecting all exiting/entering freeway traffic into a single consolidated ramp and reducing merging with thru traffic. These sort of roadways may occasionally have names/signed numbers, especially the longer multi-lane ones that are just as wide as the mainline freeway (see those along I 95 through Fredericksburg and 495 in Alexandria, VA), but generally they are both treated by traffic and designated by DOTs as just highway ramps, albeit longer and more complex than your typical slip lane or exit ramp. Since both the I 15 and US 95 ramps that were tagged as tertiary are both signed simply as exits rather than local lanes part of the main freeway, the best tag for them would be motorway links.

These sort of roadways would be better classified as links tagged based on which roads they link to rather than as actual roads since they are ramps linking roads rather than actual named roads themselves.

Same here haha. It might've just been a relic of expressway-based trunk tagging.

Technically not since it's only a stub, and trunk classification here would imply that Eastgate Road is a significant destination. Current motorway to primary configuration here should be fine as-is.

That tagging scheme would have to do more with connectivity than end-of-freeway expressway tagging. Typically trunk has been used to classify those little sections of motorways through signalized interchanges to connect the ramps on the non-freeway side with the freeway (in this case, the southbound 215 ramps with Summerlin Pkwy), though this would imply that Summerlin Parkway would be a trunk road if not a motorway, but since it primarily only serves local traffic rather then through traffic like I 11/Route 95 or bypassing traffic like the 215, primary for that little segment makes sense to me. AFAIK many other mappers would probably disagree with that conclusion since motorway renders at the same level as trunk and is thus often considered at the same importance level. However, if motorways are being classified based on physical characteristics rather than importance, Summerlin Pkwy, the motorway spur of the 93 Bus. loop in Boulder City, and the Airport Connector should be treated as freeway-standard primary roads and the 215, 11/95, and I 15 should be treated as freeway trunk roads, meaning your change to that segment of Summerlin Pkwy should be correct.

I have considered upgrading Rainbow Boulevard to trunk in the past as well for the reasons you stated, but ultimately I would have to believe that primary is the best classification for it. My initial considerations were its high traffic volumes and that it could be used for getting from Route 95 to the 215 to Highway 160, but it's still primarily local traffic using it, so I decided against it. Even though Rainbow does see more traffic than Durango, Jones, and Decatur, they all have very similar roles in the road grid, and the alternative would be to drop the latter roads down to secondary, which seems a little under-classified in my opinion. I think primary should be fine for all major thoroughfares of this nature in the Las Vegas Valley granted that they are mostly used by and intended for local traffic.

I would believe that the reason expressways aren't tagged and rendered the same way as motorways would be that it's very contentious among the community what an "expressway" is, granted that they can vary between a divided highway like US 95 north of Las Vegas/south of Boulder City, a New Jersey-style expressway that's divided and has interchanges but retains driveway access, a super-two like Route 7 around St. George, UT, or an undivided high-speed road limited access points like Route 9, also around St. George. This is opposed to a motorway/freeway which is more straightforward in concept; controlled-access, divided, and high-speed. This ultimately results in examples like the Route 73 Wilmington, Ohio bypass, which on paper is as important as the primary routes at each end of it, but it is characteristically a fully-controlled-access freeway.

The good thing about the expressway tag is that, while it doesn't really render on many map tiles aside from Americana as you mentioned, it does affect routing—which is just as if not more important than how it renders.

I would say that trunk classification is not the best tag for roads like these despite their widths and traffic volumes, as they are still only local roads. In an urban scenario like this, trunk classification should be applied only to major non-freeway highways that serve as major commuter routes to suburban/exurban communities, or as thruways for non-local traffic—essentially the most important non-freeway highways. Think of the sort of roads you'd use to pass through the city or The Las Vegas Valley doesn't have too many examples of these sort of roads considering how remote and freeway-centric it is, but Route 160 out to Pahrump is a good example of a commuter highway to a major satellite town and Route 146 is a viable alternative route to the freeways for traffic traveling between places like SoCal out to Henderson/Boulder City.

Using another, albeit smaller city which has more trunk routes closer to its urban core, Carson City has a few of prime trunk route examples. US 50 in the west heads out to Sacramento—another relatively close-by metro area, US 395 in the south is more remote but links Carson City to major satellite communities like Minden and Gardnerville and eventually towards SoCal, and US 50 in the east links to Fallon—a relatively significant rural town outside of the immediate metro area. What also makes these highways prime examples of trunk roads are that they don't exclusively serve Carson City and provide thruways for long-distance travel (for example, tourists in Reno can pass through CC via US 395 to Los Angeles, or trucks traveling between Sacramento and Fallon can use US 50 through the city). Las Vegas Boulevard, while a major, high-capacity, and famous road in its own regard, is still effectively only a business route for locals and tourists, rather than being a major inter-regional highway like the previous examples.

My reasoning for going from motorway to primary rather than going through a sort of classification gradient would be that motorway classification is based off physical characteristics while tertiary, secondary, primary, and trunk are based off importance as a road. This means that a motorway could theoretically have the importance of a tertiary or primary road but is tagged as a motorway as it has freeway characteristics (a high speed limit, interchanges/overpasses, spurs off of another motorway, etc). When the freeway ends and becomes any sort of surface road, be it a neighborhood street, suburban thoroughfare, or an expressway, the classification should be tagged based on how traffic is using it, what destinations it links to, how it serves relative to other roadways, etc., and other tags can be used to describe the physical construction, such as expressway=* and access_control=*.

While this little expressway-like stub of Lake Mead Parkway may see more traffic than the rest of the road to the east, I would have to assume this number is only trivial as the traffic would be going to and from Eastgate Road, which is a relatively minor road itself and not worth in its own merits being linked by a trunk route.

Hello, expressways should not be exclusively tagged as trunk, especially short sections such as these. The expressway characteristics of this road can be indicated with the expressway=yes tag.