A while back I had a read through the PTV rail network plan looking to summarise their view on the rollout of high capacity (in-cab) signalling. Sorry this post has been so long in coming.
This short (three minute) video explains it nicely, but one analogy is that the current system is like driving around the burbs using nothing but traffic lights to determine when to stop or go. This of course would be extremely inefficient — you could only have one car per section of road between traffic lights. So of course we drive mostly by sight, simply keeping a safe distance from the car ahead.
For trains, the stopping distances are too long to be able to drive by sight, but in-cab signalling provides the signals inside the driver’s cab instead of trackside, with the system advising how fast the train can go while still keeping a safe distance from the one ahead.
The PTV plan’s intro text on the topic describes the impact of an upgrade:
Most of Melbourne’s signalling system, known as an Automatic Block system, currently uses coloured lights next to train tracks to advise the driver of what speed it is safe to travel – essentially the same technology introduced a century ago. The signalling capability in the city and inner suburbs, where two or more lines share tracks, typically allows for average two to three minute headways (the time between trains), extending to three to five minutes on each suburban line.
Safe distance between trains is ensured by providing a signal sighting / driver reaction time, a minimum breaking [sic] distance and a safety margin.
The existing system typically operates at around 15 trains per hour and could operate at up to 24 trains per hour in an ideal operating environment. In reality, a frequency of 22 trains per hour is seen as the practical achievable capacity to ensure an acceptable level of reliability can be attained.
In-cab signalling in systems overseas sees around 33 or more trains per hour running, so obviously you get a big benefit from increased rail line capacity — if you’re going from 22 to 33, then that’s around 50% more trains. Coupled with upgrades providing more capacity in each train, you can move a lot more people.
So how much do you need to spend to get this big increase in rail capacity? Perhaps not too much actually.
A UK tender from a couple of years ago outlines the costs for this upgrade for part of the London Underground:
The contract, valued at approximately £354 million GBP (approx € 402 million euro / $ 577 million US), is a part of London Underground’s SSR Upgrade Programme (SUP). Bombardier will provide the proven CITYFLO 650 ATC system, its innovative communication-based train control (CBTC) technology, similar to that running successfully on the Metro de Madrid in Spain.
Bombardier will equip the 310 km of track line (40 km in tunnels), 113 stations, 191 trainsets, 49 engineering trains and six heritage trains by 2018, followed by a two-year warranty period.
This portion of the London Underground is roughly 40% of the size of Melbourne’s entire rail network, in terms of track length and number of trains (but with much less track in tunnels). On that basis, performing the same upgrade for the entire Melbourne network would cost about £885 million GBP, or about A$1620 million.
It’s worth noting however that Bombardier and London Underground have scrapped that particular contract, citing incompatible equipment. Obviously it’ll be interesting to see if they can re-let the contract to another supplier for a cost in the same ballpark.
Even if you took the rough Melbourne figure and added 50%, you’re still looking at around $2.5 billion, which is a bargain for being able to put about 50% more trains onto the tracks — the equivalent carrying capacity of scores of motorway lanes, but with nothing like the impact. (And the induced traffic would be train passengers, not motor vehicles.)
So what’s PTV’s plan to roll new signalling, once they get the money? In summary:
Stage 1: Sandringham trial (in part because that line is relatively self-contained)
Stage 2 (which includes the metro rail tunnel): Sandringham (full installation), City to Clifton Hill, and Sunbury to South Yarra (eg via tunnel)
Stage 3 (which includes Clifton Hill to Flagstaff tunnel): Werribee/Williamstown, Craigieburn, Upfield (including re-routing of Seymour trains via that line), Dandenong lines
Beyond stage 4 – rest of network
Also note their video includes a glimpse of in-cab signalling, at about 3 mins, 5 secs in:
So what happens now?
The plans are in place… but one of the options must surely be to roll out the new signalling before the rail tunnels, providing a big capacity boost across the network more quickly.
Either way, nothing happens until the government provides funding.
And at present, they’re a bit busy pouring money instead into the East West tunnel, despite that nobody asked for it.
- Update March 2014: the Cranbourne-Pakenham line project proposal includes upgrading that line to in-cab high-capacity signalling
- Update February 2015: PTV chair Ian Dobbs: said high-capacity signalling was a “big technical jump – like going from a Tiger Moth to an Airbus 380″. But he said it would give the state the ability to run “more trains, more reliably … closer together”.