1. Since you are waiting for a train to Punggol, and the last
train has left, I suppose what you are referring to is that the
last passenger service train has left the platform towards
HarbourFront. Now, it is known that after the last passenger
service train left for HarbourFront, there will be a yellow
maintenance locomotive that will follow it, which I suppose came
out through Sengkang North crossover, north to Punggol and back
south. What it does is to move along the track and detect for areas
where there are rail faults, due mainly to over-grinding (at bends)
and so.
You will be surprised that our wheels on MRT systems here are
changed once in a few months, at most a year, due to wear and tear,
and the track is also facing the same type of operational stress
during operation.
Back to this locomotive. It will go all the way to HarbourFront,
then back to Sengkang Depot by Buangkok south crossover. It may
stop for a while at stations, but that is due to it being too close
to the last train in front of it.
2. Every train, when it has completed its scheduled service, will
pull out of the main tracks back to the depot. This is necessary to
prevent disruption to normal service.
There are 2 crossings (for changing tracks) leading to Sengkang
Depot. The Buangkok South entrance can easily been seen when you
take a NEL train northwards towards Punggol. It is located just
before reaching Buangkok station, a crossing branching out to
another tunnel on the left.
The Sengkang North entrance can be seen when you take a NEL train
southwards towards HarbourFront. It is located just after the train
left Sengkang for Buangkok. Sengkang has 2 single-nose crossings
for changing between the north and south-bound tracks, and these
are placed closest to the station. There is a 3rd and 4th
single-nose crossing connecting a middle tunnel and both the North
and the South tracks. This middle tunnel leads to Sengkang depot.
To locate the tunnel, look out for the tunnel led by the 3rd
crossing after a train has left Sengkang. You should be able to
catch only a glimpse of it. The tunnel then moves higher above the
HarbourFront tunnel, as noted by the HarbourFront tunnel moving
lower and to the left towards Buangkok.
The crossing connecting Sengkang North entrance and northbound
tracks is the first crossing after leaving Buangkok for Sengkang.
Now you know why the whole Sengkang crossing area is so long.
Trains go to sleep after the trains' operating system has done a
check with all the components in the train, like power intake,
back-up power, communications systems, doors etc. Just before a
train goes to sleep, its will lower the "intaker" on the top of the
train away from the overhead electricity cables. For your
information, the overhead cables is the positive pole and the third
rail (white, next to the 2 rails of the track) is the negative
pole, whose potential difference is 1500V DC.
Cleaning is done at HarbourFront. At various periods of the day,
cleaners board the train at HarbourFront after passengers have
alighted. In the few minutes where the train rests at the overlay
tunnel behind the station while waiting to cross-over to the other
platform, cleaners do a quick job of spricing up the cars.
3. You can try SBSTransit website.
4. Trains wake up automatically at 5am and does a through self-test
again to ensure all components are working. Trains that failed the
test will not go into passenger service. After downloading the
day's schedule and accorded the respective Train Run Number (TRN),
which is something like duty codes (NEL uses 301-325 for passenger
service trains), they are ready to set off. Adhering to the
schedule, they will then set off. The Operations Command Centre's
(OCC) computers will also make sure the crossings are correct so
that the train can move out in time.
As for the computer systems, SMRT do have many computer systems in
place too, but they do more of an advisory role. Some systems in
use by SMRT are Automatic Train Operation (ATO), Automatic Train
Protection (ATP) etc. Similar systems are employed by NEL and most
modern rail systems around the world.
Automatic Train Protection (ATP) is in charge of ensure collisions
do not happen and trains keep a safe distance from each other.
Behind every train, ATP sets a increasing speed limit for every
track sector as the distance increases. A train behind, when coming
too close to a train will sound a buzzer and automatically slow
down to the speed limit defined for that track sector to prevent a
collision. Another type of speed limit tied to track sectors is
influenced by the default speed limit set for the track, like a
lower speed for a downhill section, rain or construction cranes
near tracks. A driver who forgot to slow down the train will upon
reaching it will have the train sound a buzzer. However, since this
is usually not a dangerous situation requiring immediate action,
the train is not automatically slowed down and the passenger train
operator (PTO) will pull the throttle to slow the train down.
Note that while ATP has ensured the safety of train operations, it
has failed before. The most famous example is the train crash at
Clementi station in the late 80's. A train from Ulu Pandan Depot
came out and parked at Clementi westbound platform. However, ATP
failed to prevent the westbound train from (then) Buona Vista from
approaching Clementi station and it is up to the PTO to see a train
in the station and e-braking his train to prevent a disaster. The
train crashed into the stationary train, but at a very low speed
such that there was actually not much physical damage but standing
passengers were jolted out of their positions and fell since there
is still the collision happening. However, ATP has been accurate
thus far, and LTA has required 98% of the track signals (which is
controlled by ATO but partly affected by ATP) to be correct in
SMRT"s annual audit.
ATO is in charge of signalling and communcation systems, which
inform the driver whether he should proceed beyond or stop at
certain points through red or white lights. This is not to be
confused with the term Automatic Mode (AM) employed by NEL.
Crossing signals are used to inform a driver whether the track is
set to the correct direction where he wants to head to (the
destination codes, which are same as station abbreviations like
MRB, JUR etc must be set by PTOs before departing from a terminal
station and of course this destination information will find its
way to VPIS at stations' plasma TVs). This is especially important
at terminal stations during peak hours where it's likely that a
train had just crossed over to another track and the machine at the
crossing has not adjusted the crossing back to the direction
required by the oncoming train, which happens as the headways are
short like 2 mins per train.
Station signals are used to inform a driver if he can proceed
beyond the station. This information is affected by scheduling and
ATP. If a train has arrived at a station early, he will not be
permitted to go beyond the point. In the event that a train goes
beyond the station illegally, ATP will cause the train will halt on
its own and OCC notified. The PTO can then speak to OCC to override
the signal setting if OCC officers allow (they can see every train
in the network and can tell if there is indeed no problem with
proceeding).
More about operation modes of trains. Trains usually run in 3
modes: Automatic Mode (AM), Control Manual (CM), Restricted Manual
(RM). AM is employed solely by NEL trains. There is some
speculation that the new Kawasaki Nippon Sharyo black trains can
use this mode too. CM is employed by SMRT PTOs for everyday normal
train operations. The PTO takes full control of the train while the
computer systems continually assesses the train's safety distance
and operations and advises the driver accordingly, with the
possibility of intervening when the situation requires it. NEL
trains can be set to CM too, that is, the customer service officers
take over the control of the train. CM is a common rail operation
term, and it is also listed in the NEL train's driver console LCD
as one of the options. Selecting it will allow you to take over the
train. RM is used only when there is some major problems that
require the train to move at very low speeds, like using a train to
couple a stalled train back to depot. Manual controlling like CM is
possible, but some functions are disabled and the speed limit is
there.
The NEL computer systems generally uses Windows 2000 with
on-the-shelf components, things like modem cards that you use on
your computer. However, the entire computer network is private and
that is the only thing that prevents intruders. Don't fret however,
as our ATM machines are Windows NT or 2000 machines too. That's why
there were news of ATMs in USA getting virus attacks like the one
spread through the Internet. for some reason, their network was
connected to the Internet. whether this is a loophole or they tried
to use SSL or VPN over Internet to save costs is not sure
though.
some old stuff about NEL:
http://www.sgforums.com/?action=thread_display&thread_id=69193&page=3
