Selective door operation

Selective Door Operation, also called Selective Door Opening (or SDO) is a mechanism employed primarily on trains (although buses with multiple doors also generally have this feature) that allows the Driver or Conductor/Guard to open the doors of a train separately.

Purpose and operation of SDO

Selective Door Operation (SDO) is a system used by trains for the safe operation of the passenger doors at short station platforms. The term Selective Door Operation is used mainly in the United Kingdom; some Train Operating Companies used the term ‘Door De-Select’. A version of this is used in other countries and on other rail systems such as the London Underground.

Selective Door Operation should not be confused with Local Door Operation (LDO), used on many trains for the benefit of train crew and other staff. It could be argued that SDO and LDO are essentially the same system, but in terms of the railway Rule Book they are treated separately.

To simplify, some trains that call at certain railway stations are too long for the platform. This caused an operational headache on old stock but was solved by Selective Door Operation. The Guard or Driver can choose which doors are to be opened so as not to allow passengers to disembark from carriages not standing at the platform. In the UK various trains, either multiple units or coaches, have variations of the Selective Door Operating system. This usually depends on what the specific Train Operating Company and/or Train Leasing Company required, either at time of purchase or a later modification to an existing train to keep up to date with regulations.

Examples of these variations are as follows:

Many modern Selective Door Opening (SDO) systems are operated / controlled by Global positioning satellites (GPS), which locate the train at the specific station. As the train pulls into to the station the GPS identifies the trains positioning and tells the SDO control (which is located on the train) what station it is currently at. This then enables the correct side of the train and enables the correct amount of coaches doors to be opened, thus aligning the length of the platform.

See also

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