SSR Resignalling Apr 13, 2021 22:50:05 GMT via mobile
Post by North End on Apr 13, 2021 22:50:05 GMT
It's got to be remembered that at the time, the majority of Amersham services ran fast along the main lines, so the realignment to give a faster curve on the local made sense, as the most benefit was provided to the traffic patterns of the day. Unfortunately a year later that all changed...
Yes, but there were significantly fewer trains in those days, both due to a lower demand and a shortage of stock or crews (or sometimes both). With lower demand and fewer trains running around there are less opportunities for delay and less need for recovery time.
The introduction of the various Migration Areas are linked to potential improvement in JTC (Journey Time capability - nothing like an old PPP acronym one in a while), once SMA5 goes in I expect we will see a timetable change on the SSR taking advantage of the performance improvements that CBTC offers.
The point about recovery times is well made. If we take the Northern Line, there’s now an all-day 3-minute service to every terminus. For the likes of Barnet and Edgware with their three platforms this means in reality the turnaround time is at best never going to be better than about 6 minutes. Add in real-life issues like your occasional driver being slow to change ends, someone holding a door open, a minor defect appearing as the new cab is opened up or whatever, and all too often this is getting down to the point where there is no breathing space at all. Drivers are allowed four minutes, but this isn’t really very long - it allows a quick toilet visit or a quick snack, but not both, and it doesn’t take much else for example finding some lost property or coming across a passenger issue for things to get very tight indeed.
So it doesn’t take much in the way of late running before you pass the point where late running won’t naturally “ride out”. In the old days if there was 10-15 minutes at the terminus, this would sort out a lot of things naturally. You simply can’t do this on railways where a late arrival at a terminus is likely to result in a similarly late departure.
Something like Merseyrail is the same with its notoriously tight timetables on certain routes - how do you manage a service like Chester to Liverpool where one end is a loop with no recovery time at all, and the other is a turnaround where the driver barely has time to walk from one cab to the other? You don’t want to turn short as both ends are the major traffic destinations. The answer is that Merseyrail sometimes remove stops, but on LU this isn’t a done thing (we once did it on the TBTC simulator when someone forgot to put it on pause during a rest break, and it did actually work rather well!).
As a passenger I hate recovery time as much as anyone else, especially if I’m on my way home. But seeing things from the other side unfortunately with the nature of today’s railway where we are really running more trains than the infrastructure ideally supports, there’s not much alternative. If you can’t build it in at the termini then it has to be elsewhere, that is the bottom line unfortunately. The only way to smooth out run-of-the-mill issues is to do just enough intervention to get things to a point where breathing space in the timetable gets everything back to where it should be. Otherwise the service will simply never recover - there’s only so many reversing points, and only so many reform opportunities!