Selective door operation
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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.
[edit] Purpose and Opperation 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 light rail systems such as the London Underground.
This is should not be confused with a Local Door Opperation (LDO) used on Multiple Units for the use of Train Crew and other staff. This could be argued as the same system, but in terms of the Railway Rule Book is treated separately. This is used for passenger, like at Conway in North Wales, but not as the norm.
To simplify, some trains that call at certain train station 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 pacific 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;
- Most Class 170 Turbostar Units, with certain exception like the 170 mark 1, are fitted with SDO. This when operated de-selected all carriages behind the location in the carriage which the train doors are being operated. So the Guard can operate the SDO, allowing any length of train to occupy the platform as long as it can take one carriage.
- Former Midland Mainline Class 170 mark 1 Turbostar Units were fitted with SDO, this was unusual in the fact it required the Driver to run the leading coach off the platform. The Driver then operated the SDO system before releasing the train doors. The result was the leading carriage only was de-selected. The Guard then closed the doors from an appropriated location. These units are currently in use with Cross Country Trains, without any need for this form of SDO.
- Class 350, 444 and 450 Desiro Electric Multiple Units use a system call Unit De-Select, this allows the Guard of the train to de-select an entire unit on a train while they are in working in Multiple from one of the Driving Cabs. Meaning that an 8 coach 350 or 450 set for example, made up of two units as each unit has 4 coaches, can have one set de-selected. The class 444 is made up of 5 coaches per unit but the principle is the same.
- First Great Western High Speed Train sets have SDO at almost all door locations. These trains are of the slam door variety and fitted with the Central Door Locking system. The Guard operates the SDO system from most door control panel throughout the train. The Guard can then either de-select doors in front of that location or behind.
