Finally, if a taxi clearance is issued it must be assured the intended taxi path is clear and safe to be used by the recipient of that clearance. Once a clearance is issued the conduct of that motion has to be monitored closely, especial in known difficult conditions.
If crews believe an ATC taxi instruction is a guarantee of a clear route, why do half of them call up for taxi with a tug blocking their way (possibly still attached) and even ground personnel on the taxiway ahead of them?
From the UK Manual of Air Traffic Services Part 1:
"Aerodrome Control is responsible for issuing information and instructions........to
assist pilots in preventing collisions between.........aircraft moving on the apron, and aircraft and vehicles on the manoeuvering area".