Since today's topic is accessibility in public spaces, here's a thread about some parts of the ADA standards for buildings and outdoor places. Information is from 1/
Let's start with surfaces. Flat and smooth is the best, to reduce trip hazards and make things easier for wheels. Sorry shag carpet fans - keep it under 1/2 inch! Sidewalk grates should be positioned so wheels don't get stuck.
Maneuvering Space! Usually we think of this for wheelchairs, but it's also important for walkers and strollers. The 5 foot circle is a common standard, and is why modern bathrooms are larger. Clear space in front of stuff, and knee space at tables is also needed.
Protruding Objects (things that stick out of a wall) can be a hazard if they're located where someone can bump into them. Regulations require these things to either extend down into the area where they can be detected by a cane.
Accessible routes are paths that are wide enough, flat enough, and otherwise free of hazards both inside and outside a building. Extra space is needed at doors.
There are many ways to do a curb ramp, and there's also the option of a speed bump "bridge" that is level with the sidewalk to cross a street.
For accessible parking spaces, it's now increasingly common to stripe an extra-wide space with a smaller aisle rather than regular spaces with a wide aisle. Why? Wide aisle happens to be the width of a parking space and people park illegally on them.
Accessibility standards also apply to stairs. There are standards for steepness, as well as requirements for handrails.
The ADA standards are just a bare minimum. There are other design approaches, for example, providing clear lines of sight and evenly lit, contrasting backgrounds to make it easier to communicate using sign language.
At one point California also explored the idea of a standard for Cleaner Air spaces, to be smoke-free, fragrance free, and using cleaning products and building materials that don't offgas chemicals.
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