Urban SHTF signal set
There is a big crisis of public services including information exchange in all SHTF situation. Set proposed below, allows you to keep some information exchange abilities.
This is not global system but in crisis situation any information can be helpful.
Depend of nature of cataclysm most important is to attract rescue groups. So chemical lights and infrared markers are good and easy choice. Big HELP sprayed on building roof or parking place can be also helpful. Duct tape can do the same.
This is good to stick a sheet of paper on destroyed building which used to be your permanent stay place. Put your name, date, reason of displacement, number of persons their condition and direction of movement. So permanent marker and field notepad is perfect.
Use duct tape and or double-sided tape to stick them to surface.
Drawing chalk is perfect for markings on rough and absorbent surfaces.
Try to know some marks recognized by most peoples in the world to share information or be able to read them for your benefit here.
These are low tech items but in SHTF situation less technology is more.
After you gave signals to rescuers try to find some resources. Read what tools are most effective in city scavenge here.
Any other ideas of affordable and handy signal devices?