G99 Taiwan Ring Expressway

The Taiwan Ring Expressway was a proposed, hypothetical expressway encircling the island of Taiwan as part of the National Trunk Highway System of the People's Republic of China. It never came into fruition, though, due to the political status of Taiwan. The People's Republic of China claims control over Taiwan, but has never administered it. Taiwan is governed by the Republic of China, which has its own highway system and does not recognize the designation by the People's Republic of China.
According to the People's Republic of China, the expressway would have passed through the cities of Taipei, Hsinchu, Taichung, Tainan, Kaohsiung, Taitung, Hualien, Yilan, Keelung, before returning to Taipei. The route of its western half was identical to that of National Highway 1 under the Taiwanese highway system.

Cancellation

In the 71118 plan of 2017, G99 was officially removed off of the books. This announcement was reaffirmed during the July 2022 expansion.
The "G99" number is currently used in the NTHS for metropolitan area ring roads, which are somewhere between city ring roads and orbitals in degree of importance.