^See e.g. Google Maps; search on "贾家源" (Jiajiayuan, the name of the junction) will show the junction which forms the southern end of the joint G106/G316 section.
China National Highway 112 runs around Beijing
Before 2013, Mainland China observed National Highway 228 as Taiwan Ring, composed of several National Expressway (Republic of China) and Taiwan provincial highways, this designation is not recognized by Republic of China (Taiwan). This observation was eventually dropped in new National Highway plans, replaced by Dandong-Dongxing Highway.
A extension plan of the highway system was announced in 2013, including extension of existing highways(101-112, 201-227, 301-330) and new highways (North-South 228-248, East-West 331-361, Connections 501-581). Only small portions of them needs to be constructed from scratch; most of the new highways would be upgraded provincial/county highways.
Another extension plan was announced in 2022, including new small purpose connection highways (601-701).