This is a very niche question, but I'm also only asking it because i don't find any answers to it anywhere else.

In my current setting, the world's population has drastically dwindled during World War I, which turned out to really be the war to end all wars, as it lead to a supernatural cataclysm (comparable to the absolute worst case of a nuclear winter) that sent the world tumbling into a new ice-age and essentially wiped-away two-thirds of the Earth's population.

One of the things i'm thinking about most is, how the sudden cut-off after the war might influence the appearance of the world, and in this case, hazard signs.

It might seem like a trivial detail, but they actually play a very important part within the setting, plastered along the edges of "Exclusion-Zones" that divide the countryside into habitable and inhospitable, with large tracts of land being extremely dim at any hour of the day, comparable to the earliest morning hours before sunrise, giving the survivors no idea as to where the possibly lethal areas even begin.

My question would be: Are there any examples of general hazard symbols that have been used during, or directly after the first world war. And what colors could make them most visible in these permanently dark, snowy conditions?

  • 1
    $\begingroup$ I remember there being a documentary about nuclear waste (perhaps related to Chernobyl?) where they discussed trying to come up with hazard markings for the ages to come. Because radiation would take so long, that they had to plan for scenarios like "somebody who isn't familiar comes across this hazardous waste" - be that aliens or even humans who have somehow lost the knowledge of radiation and are stumbling upon this again thousands of years in the future. $\endgroup$
    – VLAZ
    Jan 30 at 10:26
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    $\begingroup$ In real history, the areas throughout northeastern France that were deemed too physically and environmentally damaged by conflict for human habitation, impossible to clean, and were kept isolated, were called the "Zone Rouge" (Red Zone). Although the isolated areas have been greatly reduced over the century that has passed since the end of the Great War, part of them still remain restricted. This is how they are marked. $\endgroup$
    – AlexP
    Jan 30 at 11:53
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    $\begingroup$ @VLAZ you might be referring to the Yucca Mountain storage site? Related links: en.wikipedia.org/wiki/Long-term_nuclear_waste_warning_messages Also, a google search on "Yucca Mountain 10000 year warning" might prove fruitful. $\endgroup$
    – Gillgamesh
    Jan 30 at 14:24
  • $\begingroup$ @Gillgamesh Yes, I think that rings a bell. It's been a long time. $\endgroup$
    – VLAZ
    Jan 30 at 14:34
  • $\begingroup$ Use red and yellow colours since they increases your blood flow making you alert☢️☣️⛔🛑 $\endgroup$
    – user6760
    Jan 31 at 7:02

4 Answers 4


Europe and the United States


The 1909 Convention with Respect to the International Circulation of Motor Vehicles, which had been adopted by nine European countries by the time the Great War broke out, introduced four international road hazard warning signs. Each one was a circle carrying a large, simple icon, with a word in all caps below it.

Road sign designs from the 1909 Paris Convention

After the cataclysm, European authorities might use the same visual identity for an exclusion zone warning sign. But what icon might they choose?


By the early 1900s, the skull and crossbones had become a standard poison warning symbol across the US. The American service members who came to Europe during the war would've been taught since childhood that it meant danger. An American soldier who wanted to quickly chalk up a warning about supernatural hazards might instinctively reach for the skull and crossbones symbol. A stylized version of it—something easy to draw and instantly recognizable, like Kilroy in our world—might even become associated specifically with supernatural hazard zones.


Victorian English glassmakers gave poison bottles a distinctive look and feel by blowing them in cobalt blue or emerald green glass, often with a bumpy texture. I've also found pictures of emerald green poison bottles from Europe.

Emerald green morphine bottle from Europe

(Photo from Wellcome Images.)

I get the impression that the 1909 Paris Convention road hazard signs were often painted dark blue, so a bright green sign in the same shape might stand out, and its color association with poison bottles might help communicate danger. As luck would have it, most people's eyes are most sensitive to green or cyan-green light (depending on whether we're using all our photoreceptors in bright light or mostly rod cells in low light), so bright green signs might also be well-suited to low-light conditions, like the permanent twilight that surrounds many exclusion zones. For even better visibility, signs could use radioluminescent paint, which was introduced in the early 1900s, and became widely used during the Great War. It glows bright green.

1917 ad for a radium-dial watch.

Overall proposal

  1. Exclusion zones shall be marked with circular road hazard signs bearing the word "EXCLUSION" below the "dead doughboy" variant of the skull and crossbones (see figure).

  2. The background of each sign shall be bright green. High reflective green should be used when possible. This color shall not be used for other road hazard signs.

  3. The foreground of each sign shall be white. High reflective white should be used when possible. Radioluminescent paint should be added when possible; test to ensure contrast with background under all lighting conditions. The edge of the sign may bear a radioluminescent border.

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    $\begingroup$ Exactly what i was looking for! Very informative, i never knew there were these kinds of semi-standardized coloring conventions- $\endgroup$
    – NimRad
    Jan 31 at 9:23
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    $\begingroup$ Although green is most visible to us in daytime it's not the same at night. colors.dopely.top/inside-colors/… Yellow is the colour that is used nowadays because it is the most visible at night. Arguably as well green is a colour that humans may ignore as it is similar to plants. Red is most striking in daytime but yellow works best overall for day and night. $\endgroup$
    – HSharp
    Jan 31 at 11:57
  • $\begingroup$ @HSharp, good point about rods and cones having different frequency responses! I've revised my answer to show both the overall sensitivity peak (around 550 nm, green) and the rod sensitivity peak (around 500 nm, cyan-green). I'd like to see more support for the statement, on the page you linked, that yellow tends to be most visible at night. I could believe that NYC's famous yellow cabs are painted for night visibility... but nowadays, many NYC cabs are bright green! $\endgroup$
    – Vectornaut
    Jan 31 at 20:18
  • $\begingroup$ @NimRad, I'd never heard of those coloring conventions either—and you should fact-check them! Anecdotally, though, they might explain my sense that US cartoons often use green as a shorthand for poisons, acids, and other dangerous liquids. $\endgroup$
    – Vectornaut
    Jan 31 at 20:35

Exclusion zones are only a thing if you have the population pressures to require them and the strength of government to enforce them, likely neither being the case in your proposed scenario.

You're also talking about a period before a lot of the globalisation and standardisation of warning signs and symbols so wherever you go in the world the signs would be different.

If an area was dangerous to be in, you might hear about it from locals, there might be a crude or official signs in the local language. If you're a long way from an urban area, there would probably be nothing. Maybe someone put a couple of logs across a road as a warning, but those could well have rotted away along with the unmaintained road.

If the area is dark and snowy all the time, the people probably moved somewhere the crops would grow, so doubling down on that "nothing to see" as there's really nobody around to care.

Send your party of adventurers to the tavern and let them talk to the locals for their knowledge of the dangerous places

  • 1
    $\begingroup$ +1 People in the age of mass-media an the internet underestimate how much local contact was used in the past, and how great of a role did personal contact mean in spreading important information. 100 years ago, if you went to a new location unknown to you, it was obvious that you'd spend time in the local inn and talk with the locals to get to know the place better. $\endgroup$
    – vsz
    Jan 31 at 6:37
  • $\begingroup$ I really like this answer, it paves the way for some interesting dynamics in the setting, i like the idea of people relying on locals for information on regional hazards more than anything. Though for the exact purpose of the question i'll go for a different answer. $\endgroup$
    – NimRad
    Jan 31 at 9:26
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    $\begingroup$ @NimRad, no worries, we have an old tradition here of answering the scenario as much as the question, that's why the background information is so important. $\endgroup$
    – Separatrix
    Feb 1 at 8:12

Skull and crossbones is a classic, has been used for centuries to indicate deadly dangers.

Yellow is the popular modern choice for being more noticeable choice for low light conditions and to contrast around environment which might be suitable for your nuclear winter. Anything to make it more flourescent would help but alternatively could just have a light source near it as well.

Normally with associated text, the symbol are for ease of recognition but also for those who may not speak the language, but text would still be used.

Skull and Crossbones "Danger - Exclusion Zone" or "Radiation Ahead"

I'm sure fences would be used as well though if you want to have an exclusion zone to actually exclude people.

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    $\begingroup$ A real skull with the radioactive symbol etched on the forehead with fluorescent paint. Stuck on a spear, the jaw ajar to give it the impression of laughing at one's folly venturing forth. $\endgroup$ Jan 30 at 21:20
  • Red or Yellow
  • Skull

That's pretty much all you need if you want a generic 'It's dangerous beyond this point' sign. Red and Yellow are evolutionary 'danger' colours - plus in a dark/snowy will be quite visible.

A Skull is pretty much the universal symbol of 'this will kill you'.

After that, you might want to have a sign that articulates the hazard - if it's wildlife - a picture of like a Bear or a Lion or big thing with big teeth like a Crocadile. Electricity - the eponymous lightning bolt. Flood - a picture of Water etc.

You get the idea. Normally you would make the generic 'THIS WILL KILL YOU!' sign the big one, then you have any additional signage as secondary.

  • $\begingroup$ Red; yellow does not indicate deadly danger clearly enough in every culture. E.g. see the Goiânia accident - this was the reason why the Radiation Danger sign was changed from yellow to red and now includes a skull symbol. en.wikipedia.org/wiki/Goi%C3%A2nia_accident $\endgroup$ Jan 31 at 9:20
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    $\begingroup$ @Georg colors.dopely.top/inside-colors/… Red is actually hard to see in low-light conditions while yellow is the easiest. $\endgroup$
    – HSharp
    Jan 31 at 11:46

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