14-09-2008, 09:52 AM
alexgoei Wrote:Hello Peter,
I have reviewed your comments for the 2002 paper and have some further questions which I have entered the text in red in the appended file.
Your Control Table has no dedicated column, so yes I would put the Overrun protection in the Remarks column. In the past instead of "intelligent SPAD protection" where data looks at a track sequence to determine a SPAD has occurred, the traditional approach would have been to put any "flank tracks" in the TCs clear column (a flank track being any TC that is not in the route / overlap but is between it and signals at danger protecting that reserved path through the layout).
The disadvantage is that a single track failure can prevent the clearance of very many signals and thus require a lot of handsignalling to keep traffic moving; the wole-life safety disbenefits rather outweighting the safety advantage. Also in complicated layouts the flank tracks need to be conditioned out by point lie, or "train going away from conflict" controls. Intelligent overrun protection is equally (or more0 complex and I wouldn't recommend attempting the details- just list the key protecting signals where a SPAD would make the CT's route vulnerable. If you wanted, an alternative place to write would be in the TC clear column; "Flank tracks after SPAD at signal xxx"- but personally if you haven't got room for a dedicated column (useful to act as areminder in the exam of course) then the Remarks column would be where I'd show
PJW