For what it is worth I think stop bars should be scrapped.
It was a good idea in principle but in practice they seem to be creating more problems than they solve.
The idea, correct me if I am wrong, was to create a back up to the controller instructions by providing a visual prompt to the pilot that the instruction was for his/her aircraft. Any deviation from that was to be queried. However:
- the lights instead of the controller have become the primary means of communicating with the pilot (just what is wrong with, "the lights are stuck confirming clear to line up"
- No one is sure what to do with conditional clearances
- Controllers at busy airports are getting repetitive strain injuries
- They are too workload intensive for ATC
- ANSPS are considering only using them during low visibility
The US did not adopt them I believe because they foresaw all of the above, however now they are developing Runway Safety Warning Lights (RSWL) which do not require controller action and only operate if there is collision risk. They work off the Sensis A-SMGCS and illuminate at the same time as an audio/visual warning is given to ATC. Pilot audio will come soon and they are experimenting with on-ground TCAS alerts.
Seems like amuch better idea to me?