It's been interesting to read the single versus double deck arguments on here, just providing some technical info to back up what ssiguy2 is saying:
Smart Tracks is what everyone else usually calls suburban rail.
There are many such examples such as in German cities and the S-Bahn systems. If you want to understand what ST tracks is then probably the easiest comparisons in a newer world systems are the suburban rail systems of both Sydney and Melbourne.
Electrified one or two level trains with fewer stops than conventional subways but more than conventional commuter rail. Most have non-level crossings to keep the trains on time and the car traffic moving especially in Sydney who's suburban rail is 800km. The tickets are usually distance or zone based and are integrated with the local bus fares. They run about every 10 minutes in rush hour, 20-30 minutes during the day, and 30 to 60 minutes late night. The lines however meet at a central point downtown so as the lines intertwine closer to the city the trains become much more frequent such as GO trains do the closer you get to Union.
For the inner city/downtown population they offer subway level service {in both Melbourne and Sydney they converge into downtown tunnels} but due to the size of the system it also means people in far flung suburban areas still have a fast route downtown with far fewer transfers that most systems and better off peak/weekend service levels than standard commuter rail.
Sydney and Melbourne are both making get strides {like GO} to get rid of all the level crossings and when finally done they will effectively be huge subway/metro systems but with far lower frequency the further you go out of the city.
As rule of thumb, the station spacing in Melbourne's inner 10km ring is around 1km, denser on some lines (600-800m between the city and Clifton Hill), longer on others (1.2km from City to Caulfield) On some lines outside the inner 10km ring this rule of thumb applies, especially to northern or eastern routes. Same thing is happening with the Melbourne Metro Rail project which will have station spacing roughly every 1-1.5km as well (at one end the services will be permanently express onto the existing network and at the other there's a 2km distance between first surface station and next new underground station).
They're building stations which will be able to fit 9 x 24m cars in future (which is pushing the capex up: $9-11bil for 9km of tunnel / 5 stations), its going to be interesting to watch two great big gaping holes in the city's main drag where the line will connect with the rest of the network at the north and south end of the traiditional CBD.
The New South Wales Government actually removed level crossings way back in the 60s - Melbourne/Victoria was doing the same thing until someone had a brainfart and decided to divert the cash into Freeways instead. There's only 4-5 in Sydney metro and 100+ in Melbourne metro, new state government which is pushing Melbourne Metro Rail tunnel also has a target of 50 level crossing removals over 8 years ( 2 x terms of parliament).
Sydney's existing rail network: exclusively double deck. Melbourne's existing rail network: exclusively single deck (although we dabbled with a DD trial in the 90s). Imagine Toronto's subway trains running on a surface network, that's basically the best way to visualise the trains that run on Melbourne's network.
By way of helping you understand the type of trains which operate, here's a comparison of Mel/Syd trains to the new Toronto Rockets:
Melbourne
X'Trapolis 100 -
http://vicsig.net/index.php?page=suburban&traintype=X'Trapolis
Height: 4.2m (includes pantograph/roof equipment)
Floor height (above railhead): 1.185m
Width: 3.05m
Formation: 4 x 24.5m Motor cars, 2 x 22.7m Trailer cars, arranged: M-T-M-M-T-M (2 x married pairs of 3 car trains)
Length: 143.4m
Seats: 524
Standing capacity: 266 (comfortable)
Total capacity: 790 (comfortable). 1394 (crush load) **
Minimum headways / signalling system: 150 seconds / 24 TPH
Theoretical maximum capacity per direction, per hour: 19,000 (comfortable), 33,450 (crush) **
Vintage: 2002
Manufacturer: Alstom
** over the past 5-10 years the three types of trains on Melbourne's network have progressively had seats ripped out and therefore more "comfortable" standing room is created and also more crush load capacity. A trial which will commence over the new few years on the Sandringham line (services on this line can operate independently of the rest of the network) there's going to be a new CBTC signalling system trialled where frequencies will probably come down to 90-100 seconds - if trial is successful, it'll be progressively rolled out across the entire network / 16 lines.
Toronto
Toronto Rocket
http://en.wikipedia.org/wiki/Toronto_Rocket https://www.ttc.ca/About_the_TTC/Operating_Statistics/2013.jsp
Height: 3.137m
Floor height (above railhead):
anyone care to fill the gap/point me in the direction where this data can be found?
Width: 3.14m
Formation: 6 x 23.19m cars
Length: 139.14m
Seats: ~400
Standing capacity: 700
Total capacity: 1100 (this is just off numbers I can find, I dare say TTC trains can crush a lot more?)
Minimum headways / signalling system:
anyone care to fill the gap/point me in the direction where this data can be found?
Theoretical maximum capacity per direction, per hour:
anyone care to fill the gap/point me in the direction where this data can be found?
Vintage: 2010
Manufacturer: Bombardier
Sydney
A Set / "Waratah"
http://en.wikipedia.org/wiki/Sydney_Trains_A_set
Height: 4.40m (double deck and includes pantograph/roof equipment)
Width: 3.03m
Formation: 8 x 20m cars
Length: 163.14m
Seats: 896
Standing capacity: ~300
Total capacity: 1210 *
Minimum headways / signalling system: 180 seconds / 20 TPH *
Theoretical maximum capacity per direction, per hour: 24,200 (Crush will be higher). *
Vintage: 2011
Manufacturer: Reliance Rail
* In Sydney/NSW you will frequently hear politicians and others refer to "reliable frequency" - and these are the publicly available "reliable capacity" numbers/aspects. The fact of the matter is Sydney's existing network can handle more than 20 TPH / 180 second headways but crushing DDs with passengers, as we all know, slows boarding/alighting and therefore impacts capacity.
Based on my observation at some city circle stations up there I've seen trains run 90 seconds apart (a train will be at the platform and the next will be stopped, in the tunnel, 1-2 signal blocks behind the train at platform. This frequency of service is common on the city circle but the congestion quickly dissipates beyond the inner city as lines branch off one another).
At the end of the day it's a lot harder to get a better set of theoretical numbers for Sydney's actual capacity with DDs than it is compared to Melbourne's.