Upon BTS extending the original 3-car train-sets to provide 4-car train-sets, all 35 trains of Siemens manufacture are now of four-car configuration, comprising two motored cars, with driving cabs, one at each end of the 4-car configuration, with two intermediate trailer cars. These are of the following types :
- A-cars, two motored cars each with driving cabs.
- C-cars, two trailer cars, non-driven, with auxiliary power supply for the air conditioning systems and passenger saloon lighting.
One of two C-cars is the new C-car named - “C1-car”. There are major new features on the C1-cars, namely :
- Tri-furcated stanchions for passenger comfort while standing mid-car at the sliding door areas.
- Wheel chair parking with handrail and safety belt at one end of the new C1-car.
- Individual auxiliary inverter, without battery, to supply the air-conditioning and saloon lighting.
- New braking system based on microprocessor control and diagnoses, type EP2002.
- Two roof-mounted refrigeration circuits utilizing R407C refrigerant
The 4-car train configuration comprises A-C-C1-A as shown in the following figure
Traction system power supply, 750V DC, is derived from the track-side located third rail traction power distribution system, fed into traction converters to control and supply AC electrical power to the traction motors fitted on each of the axles of A-cars. Similarly, each of the two intermediate C-cars pick-up 750 V DC power from the third rail for conversion by Auxiliary Converter Modules to 400 V AC and 110 V AC for powering the air-conditioning units and for battery charging, respectively.
The length of a 4-car train is 86.6 meters, car width 3.12 meters, with an overall passenger capacity of 1,490 persons, all seats occupied and standees creating a load condition 8 persons per square meter. There are 42 seats per car, (168 seats per train). The passenger sliding doors are of the top hung, electrically powered, outside sliding type, providing 16 passenger doors per train-side. The minimum width of a sliding door-way is 1.4 meters. The car-body is constructed of welded stainless steel with a fully equipped air-conditioning system and light-screening on windows.