Recently we have heard of the complaints following the Distance Fare implementation on 3rd July 2010. More commuters voiced their displeasure at SMRT for running their trains with such crammed situations, and ‘where are (our) trains?!’, they shouted. Well, fact is much of the system is already fully jammed by themselves, and nothing much could be done other than;
1. Coupling two 6-car train together, creating a (京急本線 快特) 12-car train (mind which doors will be opened; only 24!),
2. Changing to C-ATS system (forget it, no space for signals!),
3. Using a new CS-ATC system (there may be improvements).
Let me include a small explanation here.
Each train is ran on the ATC (Automatic Train Control) theory. Leaving all the ATO and ATP aside, the ATC is the root of the operating system. The ATC system used on SMRT EWL and NSL is akin to the ATC-4/CS-ATC of Japan, which started operations in 1971 on the JNR Joban Kanko Line (常磐緩行線)/Eidan Chiyoda Line (営団地下鉄千代田線). It consists of signals entirely displayed in the cab (hence CS, Cab-Side) without speed signals at the trackside (in the case of WS-ATC, Way-Side).
ATC speed limits are 0, 20, 30, 40, 60 and 80 km/h, and are consistent through the three types of trains on the system.
Whenever passing over a signal transmitter, the speed limit is transmitted to the cab and the computer slows down the train automatically. The higher the running speed, the larger will be the distance, to create safe separation between trains.
For example, when approaching a station that is occupied (train on the line), the signal would reduce from 80>60>40>30>20 and train will coast the remaining distance to hit the 0 km/h point where brakes will bring the train to a full stop, in this case, 6-car length from the station’s end (another train’s rear). All signals are transmitted via track-side transmitters to the train. When the train in the platform moves off, it must clear 6-car length away from the station’s head in order for the following train to start moving, with signals incrementing 0>20>40 and so on.
When braking, ATC-4 deploys full service brake (B3, about -2.88 km/h/s) to reach speed limit, hence the discomfort when the train slows.
Each block can only accommodate one train. Stations have protective buffers, as mentioned, 6-car in length, forward and rearward of the station. Hence trains cannot be cleared without having this space freed up.
Is it still hard to understand the station block? Here is one photo to illustrate.

A Siemens C651 (Series 200) is stopped in the station with doors opened. A KHI C151 (Series 0) rolls at below 20 km/h and about to stop 6-car length from the Siemens. Now, you could insert another train in between them, and the couplers would just nice be touching each other when the trains become stationary.
One rather illegal way to close up this gap would be to switch to RM (Restricted Manual) mode right after stopping, however, this is counted as an illegal operation during revenue service and will likely endanger passengers and trains.
Chiyoda Line changed to new CS-ATC (1-brake-notch speed control, digital ATC) in 1999. The only ATC-4 zone left in Japan is on the Tokyo Metro Yurakucho Line, between Shin-Kiba (新木場) and Shintomicho (新富町) stations, and this too is slated for progress to new CS-ATC in 2011.
So will the new CS-ATC land in Singapore to hope to improve the running frequency? If our system is still:
1. Three brake notches,
2. Drivers not well trained to stop accurately, stop with specific technique (N>B1>B3>B1>N or similar).
then no ATC system will be sufficient. Go back to the semaphore, not that its bad (it means back to the basics)!