You cannot spot dangers on a map.
Another entry from my day trip to Tokyo.
Captured this sign at Jujo Station, Tokyo. It was telling people not to text while walking; a new type of communicative purpose to be had by a public sign due to the spread of smartphones.
Also, in the sign, one Japanese sentence ironically tells that "You cannot spot dangers on a map." This may be for those who look at maps on their smartphones on the platform. Smartphones are not just for texting, but also for finding a route.