Does the tunnel area begin after the gas station? I think it only ends on the southbound carriageway there but it starts on the bridge over route 7 northbound.

Discovery Bay Tunnel is currently highway=secondary, so I'd say the wiki page isn't all that accurate. Try messaging KX675 (writer of the wiki page).

If you're going to change it, at least change the whole thing instead of doing it inconsistently.

I don't know, honestly, I got corrected when I did this once so it's probably incorrect. The tunnel area probably starts on the eastern side of the exit.

The "control area" designation is entirely separate from the "expressway" classification and so since North Coastal Rd is not in the gazettal it should be tagged highway=primary or highway=secondary.

Why did you leave the end of the road highway=motorway?

The EPD document is from 2004 and states "will be gazetted". The Highways Department document is a later document voiding the designations in the previous gazette from 1 December 2009, which presumably voided the ones in the previous, and so on, so if it was an expressway at its opening it isn't one anymore. (One badly-scanned PDF from 12 years ago is not really a good source for the question "Is this road an expressway?".)

I'm not sure what definition of "highway" you have but every single road listed in http://www.gld.gov.hk/egazette/pdf/20101448/egn201014487570.pdf is signed all over the place with green signs and kilometre markings, and has "expressway begins" and "expressway ends" signs (see https://commons.wikimedia.org/wiki/Category:Diagrams_of_road_signs_of_Hong_Kong) at every entrance and exit. Ma On Shan Bypass is not one of those roads.

The road is also not in the next link's document, which is supposed to be an exhaustive list of every expressway in Hong Kong. Ma On Shan Bypass does not have expressway signage.

Thanks, was going to do this in cleaning up woodpeck/Frederik Ramm's reversion.

PLEASE don't delete connector ways in intersections like that because it messes up the turn restrictions. Search the OSM wiki about them.

The road signs there show that the expressway only starts 100m to the east of where the two carriageways converge to form four lanes with a divider, so the eastern end should be tagged as highway=motorway_link or highway=secondary.

Your first link is from 2004 and is not by the Transport Department, meaning it's not a reliable source for if a highway is an expressway. Detail could have been lost in translation.
As your second link clearly states, only the part of Ma On Shan Road at the intersection with Tate's Cairn Highway (i.e. the exit 7 slip roads) should be tagged highway=motorway_link or highway=motorway. Not the entire road.

The distance markers don't make the roads motorways. The government just adds them inconsistently to trunk routes, I think. In the last several years it has been according to whether a road is on this list http://www.gld.gov.hk/egazette/pdf/20101448/egn201014487570.pdf.

Cheung Pei Shan Road is not a highway for any of its length and is therefore (from exit 25A to exit 24C) tagged as highway=trunk.

As far as I'm aware this road is not gazetted as a highway and takes highway=primary.

Should be highway=trunk. A few months ago bbkwan incorrectly changed West Kowloon Corridor to highway=motorway and that has yet to be fixed

Incorrect; this road should be highway=trunk as it is a trunk road but not an expressway.

FYI the reason the situation currently looks so inconsistent is because user 00crashtest, for some reason, decided without any community discussion whatsoever to tag every road without an at-grade intersection as highway=motorway. I have asked [email protected] to revert this change, per https://help.openstreetmap.org/questions/47773/problems-with-mass-retagging-and-others.

Don't change the highway type of roads any more, please. That was settled 5 years ago. Do something more productive with your time. You are obviously capable of editing.

Are you just bad at English reading comprehension or did I waste half an hour trying to explain to you how expressways have a special classification?