Do you need a class b cdl or a class c cdl to drive a 16000 lb trolley with air brakes?

Class C. Since the vehicle weighs less than 26,001 pounds you don't need a Class B CDL, but you can't put an air brake endorsement on a non-commercial driver's license so Class C it is. Make sure you bring a vehicle with air brakes to your road test; if you don't you'll receive a "no air brakes" limitation on your license.

However, since a trolley is a rail vehicle, and not a road vehicle, it's likely you won't need a CDL for it, but will have to undergo company training to operate it.