Automatische treinbeïnvloeding

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Automatische TreinBeïnvloeding or ATB is a Dutch system of Automatic Train Protection developed in the 1950s. Its installation was spurred by the Harmelen train disaster of 1962.

ATB operates by the train collecting electrical signals from line-side apparatus which will override the driver's controls in the following situations:

a) failure to brake for a red signal (ATB makes an immediate brake application)
b) failure to reduce speed at a caution signal (ATB will slow the train sufficiently to stop at the next signal).
c) failure to observe speed limit (ATB slows the train) (such as around a sharp curve or low speed turnout)

For completeness, the ATB should also:

d) restrict the speed of the train after passing a signal at danger. This was a factor in the Glenbrook train disaster.

Speed limits are set in 5 steps: 40 km/h, 60 km/h, 80 km/h, 130 km/h and so-called volle materiaalsnelheid (i.e. full speed allowed for that type of train), which can be 140 km/h at most. If the train's maximum allowed speed is lower, the 130 km/h setting is omitted.

[edit] Design flaws

One of the early system's major design flaws is the inability to intervene at speeds below 40 km/h. Several accidents at train stations and railroad yards occurred because the driver failed to stop at a red signal and ATB didn't intervene, because the speed was below 40 km/h. Another problem is the maximum speed set to 140 km/h. Though there are tracks with a design speed of 160 km/h, they cannot be used up to full speed because ATB Eerste Generatie or ATB-EG (First Generation, early system) doesn't allow that.

[edit] Enhancements

To overcome the design flaws, a second generation ATB (ATB Nieuwe Generatie or ATB-NG = ATB New Generation) has been developed which more or less overcomes the aforementioned problems. The speed is now set in 10 km/h intervals from 0 through 200 km/h and the amount of braking is relative to the weight of the train. Though (or maybe because) the early and new systems are totally different and completely incompatible from the design point of view (though a train equipped with ATB-NG also has an ATB-EG system on-board, so the system has backward compatibility), they do not interfere with each other: they both can safely be installed at the same track. Also, there are enhancements to the early system, called ATB-Plus (lifts the 140 km/h maximum system speed) and ATB-Plus-Plus (designed to further reduce Stop Tonend Sein or STS-passages = Signals Passed At Danger).

Another problem with ATB is the patent held by ACEC-Alstom, which doesn't allow other manufacturers to supply the system and offers poor interoperability with other systems. This is one of the reasons the Betuweroute receives the European standard European Railway Traffic Management System (ERTMS).