Tuen Mun Road (Tuen Mun Central) is not a motorway

Tai Po Road (Sha Tin Central) is also not a motorway

The access restrictions here are wrong. Parkes Street allows all kinds of traffic to go through.

I am going to put this issue to the mailing list and see what's the community concensus

The section with highway=tertiary should allows all vehicles (except tourist buses) inside, and the service roads should allow only franchised buses.

For bus and share_taxi, yes.
For minibus, actually that tag is invented by me as I can't find the international equivalent. If you know better key than minibus, feel free to use it.

psv=* tag should contains values such as
yes (public service vehicles allowed)
no (public services vehicles not allowed)
designated (roads designated for public service vehicles)
etc.,

As the wiki says "for values see access=*", the values such as "bus", etc. on access, psv tag is nonsense. What does that mean for "bus" access of public service vehicle?

If not all public service vehicles are affected on that road, more specific transport modes (e.g. bus=*, share_taxi=*, taxi=*) are used. For example, "vehicle=no; bus=designated" is used on a bus only road.

In the restore state a vehicle running straight on Mong Kok Road has to go through two traffic signals, which is wrong in reality.

Btw, it is impossible to right turn from Nathan Road to Mong Kok Road now so the redundant section has to be removed.

This is to properly deal with the issue of dual carriageways: we need to ensure that vehicles only passes one highway=traffic_signal node no matter how they turn, and in fact, the vehicles "passes the traffic signal before the pedestrian crossing"

For example, if two dual-carriageways intersect with each other to form a #, where right-turning but not U-turning is allowed, tagging in the "proper way" is just done by four no_u_turns, however if to avoid "via way", then two additional short sections forming an X has to be given and "no right turn" restrictions has to be put on the # (to avoid right-right-turning), in addition to the "no u turn" restriction from the diagonal to the opposite way.

I think that, as mappers, we should map restrictions according to proper usage of tags, instead of "working around" to complicate the data.

For example, vehicles running from south to north along Nathan Road crossing Mong Kok Road will need to pass 1 vehicle traffic signal and 2 signal-controlled pedestrian crossings. Therefore, they are not equivalent and cannot be replaced by the other.

Properly implementing restrictions should be done using a correct restriction:no_u_turn, specifying the short section as role "via", but not redundant sections.

crossing=traffic_signal only implies pedestrian traffic lights. It does not imply traffic lights for vehicles. It is possible for vehicles to cross a light-controlled pedestrian crossing without an associated vehicle traffic light, as in the case of most intersections