In my area, you can register for an ASD card.
Emblazoned across the front is:
ATTENTION!
POLICE/EMERGENCY SERVICES
I have an Autism Spectrum Condition
Turn over for more information
On the back it has my name; the details of my emergency contacts; I find social communication difficult; I am likely to be extremely anxious in unfamiliar situations and that my behaviour may be perceived as strange or threatening.
Although I am yet to need to use it, having the card in my wallet is somewhat reassuring when I am in public.
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"Every day, once a day, give yourself a present. Don't plan it, don't wait for it, just let it happen. " - Special Agent Dale Cooper, Twin Peaks