Likely one of the largest expressway systems that is unmapped, I've started to map out the Guangdong (CHN-GD) provincial freeways (about 1000km) now that most of national expressways (chng) in the province are mildly completed (which I'll go back to set new intersecting waypoints).
Chinese and
English Wikipedia cover the expressways pretty well (though some of the parent pages are a few years dated), and all very well mapped on OSM. They are all tolled so entry points from toll plazas are clear.
For reference:
chng;CHN;China National Expressways;TMblue;1;preview
chnah;CHN;China UNESCAP Asian Highways;TMred;3;preview
And we'd be adding:
chngd;CHN;Guangdong Provincial Expressways;TMyellow;2;devel matching the color of distinguishing top color of the shield.
There is a Draft PR with the .wpt routes I've completed:
https://github.com/TravelMapping/HighwayData/pull/7535/files