A sign in Tianjin, China, points toward two roads, which, although they have different names, are both labeled “SHANXI LU”.
The two roads are named after adjacent Chinese provinces: Shānxī (山西), whose largest city is Taiyuan, and Shǎnxī ( 陝西 / 陕西), which contains Xi’an. So “Shanxi” would appear to be appropriate for both if tone marks are omitted, which is, obviously, sometimes definitely a bad idea.
But because these names are both often used and leaving off the tone mark in their romanized forms could lead to confusion, the PRC authorities long ago decided to alter the romanization of Shǎnxī by borrowing a trick from Y.R. Chao’s tonal spelling system; in this exceptional case, a doubled a is used to represent the third-tone a in Shǎnxī, rendering the province’s name as “Shaanxi”. (This is not intended to change the pronunciation in the slightest, which is still Shǎnxī in modern standard Mandarin. Pronouncing “Shaanxi” with a drawn-out a — Shaaaaaaaaaaaaaaaaaaanxi — is incorrect.)
In Gwoyeu Romatzyh, a first-tone a is spelled simply a, so “Shanxi” could be said to use this as well. And in the old postal system romanizations that predated Hanyu Pinyin for the names, the provinces were “Shensi” and “Shansi”.
So the signs in the photo should read “SHANXI LU” for 山西路 (Shānxī Lù) and “SHAANXI LU” for 陕西路 (Shǎnxī Lù). The local authorities, however, say they can’t do anything to change this:
Tiānjīn Shì Dìmíng Bàngōngshì de gōngzuò rényuán biǎoshì, ànzhào “Tiānjīn Shì dìmíng guǎnlǐ tiáolì” de guīdìng, dìmíng de Hànyǔ Pīnyīn Fāng’àn yào yǐ Hànyǔ Pīnyīn hé pīnxiě guīzé wéi biāozhǔn, bùdé shǐyòng wàiwén pīnxiě. Tóngyàng, Tiānjīn Shì yǔyán wénzì péixùn cèshì zhōngxīn de gōngzuò rényuán yě biǎoshì, xiàng Shānxī Lù hé Shǎnxī Lù de Hànyǔ Pīnyīn pīnxiě fāngshì quèshí wúfǎ gēnggǎi.
This is absurd. “Shaanxi” is not a “foreign-language spelling” (wàiwén pīnxiě). The name is in Mandarin, China’s official language, and Shaanxi is China’s own spelling for this, as should be no mystery to anyone who has access to a map of China published in the last few decades. Also, Hanyu Pinyin’s rules — which are based on words, not syllables, and most definitely not on Chinese characters taken in isolation — take this exception into account. Using “Shaanxi” to refer to 陕西 Province is perfectly acceptable in Hanyu Pinyin.
source: ‘SHANXI LU’: Nín cāi shì nǎ tiáo lù? (SHANXI LU 您猜是哪条路?), Měirì xīn bào (每日新报), December 29, 2006