Availability: 

Transportation exists and is available when needed (e.g., transportation is at hand, evenings and/or weekends).

Assessibility:

Transportation can be reached and used (e.g., bus staris can be negotiated; bus seats high enough; van comes to the door; bus stop is reachable).

Deals with standards relating to conditions such as cleanliness (e.g., the bus is not dirty); safety (e.g., bus stops are located in safe areas); and user-friendliness (e.g., transit operators are courteous and helpful).

Affordability:

Deals with costs (e.g., fees are affordable; fees are comparable to or less than driving a car; vouchers or coupons help defray out-of-pocket expenses).

Adaptability:

Transportation can be modified or adjusted to meet special needs (e.g., wheelchair can be accommodated; trip chaining is possible).