I've been traveling around Japan recently and I've come across these stickers with the letter "G" and one or two arrows in many streets in Tokyo, Osaka and Kyoto.

Some streets have dozens of them. What do they mean?

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    Note that yellow letters on green ground however denote escape routes in case of godzilla attacks. – PlasmaHH Sep 27 at 14:55
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    Along similar lines is when you're in California and you see "USA" spray-painted on a road or sidewalk. It's not patriotic graffiti, but a mark of a buried pipe or cable; it stands for Underground Service Alert. – Nate Eldredge Sep 27 at 18:22
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    @Lightness Are you on 28k dialup? – John Sep 28 at 1:50
  • @John No but having bandwidth doesn't mean I enjoy it being wasted! And some people are on slower connections. Anyway, just an observation - a quick optimisation would not reduce useful quality – Lightness Races in Orbit Oct 1 at 12:33
up vote 72 down vote accepted

It's a marker for a buried gas pipeline. Arrow points to where the gas heads to. The marker is used to easily identify which areas need to be dug up, in case maintenance (e.g. pipe replacement) is needed, or to avoid the pipes during excavation work.

Reference (in Japanese): http://www.yotsugi.co.jp/products/detail/233

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    Why the Latin letter G and not the first Japanese character in the Japanese words "gas"? Not universal or ISO enough? – cat Sep 26 at 19:11
  • @cat jisho.org/search/gas It looks like only one character would not be sufficient to know what might be meant. – Andy Sep 26 at 23:30
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    @cat I don't know the reason, but they sometimes use nails with the word for gas is spelled out. There are nails that also use just a G. See link – DXV Sep 27 at 0:23
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    gas in japanese is just ガス which is romanized as Gasu (and pronounced basically the same as terminal u are often ghosted), and all Japanese are required to study Japanese and so will know this romanization. why not ガ? I'm not sure... – MichaelChirico Sep 27 at 12:49
  • @Andy: "G"' isn't sufficient to know what might be meant either (grain? glass? gum? gas?). It's a convention born out of the intention to keep things simple, and a similar convention could be drafted using a Japanese character. – Flater Sep 28 at 7:53

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