How much of a disability does one have to be in order to get a reduced fare. 10%-20%- 30% ect.

If you have a walker wheel chair or or 55 years old or blind

That can be answered by the Valley Metro Mobility Centre. I can say that if you use a walker or electric mobility device ( specifically a power chair or scooter), you can go to the office accross from the Mobility Centre and request an application for a Platinum Pass which you will not pay anything for. The cost of the the pass is covered by the US ADA (Americans with Disabilities Act.

And you must have the proper ID card in order to get a reduced fare bus pass for an entire month.

Blind pr mobility limited. Percentage doesn't count. Just go there for a short interview.