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It’s all automatic for Metro

DUBAI — The Dubai Metro has adopted the state-of-the-art Automatic Train Control (ATC) System named Seltrac S40. The system uses the moving block principle in a communications-based train control environment.

Adnan Al Hammadi, Director of Construction, Rail Agency, said, “The Automated Driverless System is completely safe and reliable. Safe separation behind the preceding train is dynamically calculated based on the maximum operating speeds, braking curves and locations of the trains on the guideway. Because of the high resolution of position, the following train may safely approach a safe braking distance from the last verified position of the rear of a preceding train, based on the maximum allowed speed in that section of the guideway. In many applications, a significant reduction in headway relative to fixed block systems is possible, since the train need not be stopped at the entrance to an occupied fixed block.”

“Unlike the traditional signalling systems, the primary design goal of a moving block system is to provide greater capacity and reduced train separation distance through improved position resolution and movement authority updating rate. Energy efficiency effects can be achieved through general optimisation of driving style and traffic flows,” he added.

The ATC helps reduce human resources expenditure and improves safety.

A safe braking model has been created for the entire guideway. From this, a ‘safety distance’ is determined and the wayside vital sub-system will ensure that it is always maintained between trains. This ‘safety distance’ is a fixed distance between the commanded stopping point of the following train and an obstacle which may be the confirmed position of the rear of the preceding train. This distance is selected to allow for a series of worst-case conditions to exist and still ensure that fail-safe separation is maintained.

Vital supervision of safe train separation is implemented by providing information on the maximum allowable train speed and the current stopping point to the on-board sub-system. A real-time communication is updated cyclically to ensure that continuous updates are available to the train. The train, therefore, can safely operate within the envelope defined by the maximum speed, the confirmed stopping point, the braking curve and track grading.

Currently the ATC system is in its last stages of design. Testing of some hardware equipment will begin in July. During operation, the ATC system will be continuously interfacing with many different systems, namely the Rolling Stock, the Power Supply, the Platform Screen Doors, the Operation Control Systems, among others.