Eligible users are defined as persons who have a permanent physical or cognitive disability that is sufficiently severe that they are unable, without assistance, to use conventional transit. Trips must be booked in advance and resources are limited, so only people who have significant disabilities will be accepted. You can also apply for a discounted transit pass.
As of October 2021, HandyDart riders will be able to use a Compass card to pay for trips. This link has all the information about setting this up.