Recent content by Tomnick

Rushing to put signals back behind a train is a sure fire way of putting the section signal back too soon. Once the home signal's back, it's definitely protected in rear (it should be anyway, as you usually can't give a fresh 'line clear' without the home signal at danger), so there's no...

The main focus is, sensibly, on the signal indications themselves and the implications for drivers. There's relatively little emphasis on what the different modes of signalling (AB, TCB, etc.) actually are. I find, generally, that understanding of the underpinning principles is very poor within...

Anywhere that I've ever come across with such an arrangement, it's been provided for all signalled moves – indeed, it's far more common for shunt moves, as passenger routes over mechanical facing points are relatively rare. Worth adding, perhaps, that it's often possible to fully reverse the...

This isn't correct – a mechanical set of points will often, if not always, have mechanical detectors in the wire run for any semaphore (main or shunt) signals reading over them in the facing direction, unless they're electrically detected. It's possible to get the lever controlling a set of...

If the points that become facing are mechanical, and have no electrical detection, how do you know that they've responded to the lever movement and are fitting up correctly if there's no signalled move over them? If there's mechanical detection, then that'll act only on the signal(s) reading...

It's on the Loop Line, all in tunnel, and presumably reflects London Underground practice. There are some repeaters, but not all stop signals have a repeater in rear.

Yes, absolutely. I think we all agree on that. The misconception is that that means that it's Absolute Block, and it's a common misconception, perhaps because of the relative rarity of semaphores on pure TCB (rather more common at AB/TCB fringes though, where generally AB only applies to the...

Greenford is one such location! Swinderby, too.

It shouldn't be – it *really* shouldn't be. The presence of semaphores does not equate to Absolute Block. You can have AB without semaphores, and you can have semaphores without AB. It's an important distinction, and alarming that this misconception is so widespread.

Greenford isn't worked under AB regs in any direction, though. On the other hand, the vast majority of boxes that *do* work AB have at least some track circuits – I can't think of any that don't at least have a berth track circuit in each direction.

Yes, I see what you mean, and you're right. In this case, the TPE would surely have closed the gap enforced by the Chinley - Edale section in the time taken for the stopper to call at both Hope and Bamford in the same signal section. The extra stop signal would at least let it get on the move...

The distant signals over the Hope Valley now are all either: - Existing distant signals in the AB territory from Earles westwards. This is governed really by the distance between block posts, with IB signals roughly equidistant between Edale and Earles, it's all just a bit too far apart for...

Doesn't mean that it's not under Absolute Block regs (which I think it is, albeit somewhat muddied by the fact that it works TCB in one direction but not the other, to the north).

Worth noting that there's been a significant, very noticeable dip in the Down line at that location for years – it's obviously got worse, but it looked bad before!

The longest section on the approach is Chinley to Edale, which is only a mile or so longer than the length of Cowburn Tunnel – so, even if it were resignalled, you'd still have a relatively long section there as a constraint. Edale to Earles is broken up by an IB. I'm surprised that an extra...