Machines like turnstiles, ticket machines have a condition value, they could be seen by hovering your mouse on them. With a staff equipped with tool kit, you can actually maintain these machine before they potentially break. This is good for both your station and your staff, as repairing a machine takes very long, causes noxious fumes and would reduce your station's reputation. Regular maintenance of machines would grant your staff experience, reduce the time to fix a machine, prevent the generation of noxious fumes, and keep your commuters happy.