The ADA provides excellent guidance and fact sheets on design and access requirements. Here's a short excerpt from their Fact Sheet on Doors.
Which doors should be accessible?
- At least one door should be accessible at these locations:Each accessible entrance (at least 60% of public entrances in newly built facilities must be accessible to individuals who use wheelchairs or have mobility impairments).
- Each tenant space in a mall or other building with multiple business
- Accessible rooms and spaces within buildings.
- Entrances to buildings from all parking structures, tunnels or elevated
- At least one restricted or secured entrance (if applicable).
- Along each building’s required route of escape or
- Public entrances serving different fixed routes within transit