staff and ticket
The operation of a
bidirectional single track line has obvious problems, the most serious of
which is the possibility of two trains traversing the line travelling
towards each other, both drivers unaware that the other is using the line.
The simplest method of controlling such a line is to only have a single
engine operational, on the basis that a single train cannot collide with
itself, and in the absence of another engine, there is nothing else for it
to collide with. Such a system is known as 'one engine in steam'. Such
schemes were used, and indeed still are used on some heritage railways and
branches of national networks. The main problem with such a scheme is that
it is only suited to a completely isolated piece of single track line.
Where the section has to be integrated into a larger railway system, it is
Instead, rather than rely on a single engine, reliance is placed on having
a single physical object available for the single track section and
ruling that only if an engine driver is in physical possession of that
object, is he permitted to traverse the single line section. That object
is known as a token and is identified as to which single track section it
The token system was developed in Britain in the 19th century, to
facilitate safe working of single-line railways. If a branch line is a
dead end with a simple shuttle train service, then a single token is
sufficient. The driver of any train entering the branch line (or occupying
any part of it) must be in possession of the token, and no collision with
another train is possible. For convenience in passing it from hand to
hand, the token was often in the form of a staff, typically 800 mm long
and 40 mm diameter, and is referred to as a train staff. Such a staff is
usually literally a wooden staff with a brass plate stating the two signal
boxes between which it is valid.
In UK terminology, this method of working on simple branch lines was
originally referred to as One Engine in Steam.
Using only a single token does not provide convenient operation when
consecutive trains are to be worked in the same direction. The simple
token system was therefore extended: if one train was to be followed by
another in the same direction, the driver of the first train was required
to be shown the token, but not take possession of it (in theory he was
supposed to physically touch the token, but this was not strictly
followed). He was given a written authority to enter the single line
section, referred to as the ticket. He could then proceed, and a second
train could follow.
Seeing the train staff provided assurance that there could be no head-on
collision. To ensure that the ticket is not issued incorrectly, a book of
numbered tickets is kept in a locked box, the key to which is permanently
fastened to the token, or is the token. In addition, the lock prevents the
token being removed until the ticket box is closed, and it cannot be
closed unless the book of tickets is in the box. Once a ticket is issued,
its number is recorded in a Train Register book, and the token is locked
in a secure place. This system is known as staff and ticket.
In a variation on this principle, called divisible train staff, a section
of the token referred to as the ticket portion was designed to be removed
and handed to the driver instead of a paper ticket.
The staff and ticket system was still too inflexible for busy lines, as it
did not allow for the situation where the train intended to carry the
actual token was cancelled or running very late. To provide for this, the
electric train token system was developed. Each single-line section is
provided with a pair of token instruments, one at the signal box at each
end. A supply of identical tokens is stored in the instruments. These
instruments are connected together electrically, and one token can be
removed from either instrument provided that both signalmen co-operate in
agreeing to the release. When a token is "out" a second token cannot be
removed, but when the token is put into either instrument, a token can
then be removed from either instrument. (There are variations on this
sequence of events.)
By this means, it was ensured that at any one time, only one token was
available to be issued to a driver. Tokens belonging to adjacent sections
have different configurations to prevent them being inserted into the
Passing a miniature staff between station and train, with the use of a
hoop. In a basic railway situation, the token can be collected personally
by the driver at the start of his work on a branch line, and surrendered
by him at the end of his work there.
Where the single line section is part of a through route, then it is
likely that each passing train would require to surrender and collect a
token at each token station. Where the trains stop at every station this
is a convenient arrangement, but where some trains run through without
requiring to make a call, it was necessary for the signalman to exchange
tokens with the fireman (in the case of steam trains) as the train passed
at slow speed. In the case of driver-only operated trains, the train must
stop for the token exchange.
A large staff could be handed over without any special apparatus, but if
the system in use employed miniature staffs, tablets or key tokens, these
were usually placed in a leather pouch attached to a hoop, and the fireman
could put his arm through the hoop held up by the signalman, and vice
versa as the locomotive ran past. In UK practice the permitted speed for
this was 15 mph in daylight.
Fixed token exchange apparatus was used on some railways. Trackside
equipment was fitted near each signal box to hold the pouch containing the
token and to receive the token pouch that was being given up.
Electronic Token Block (RETB)
The development of modern
electronics and "vital" or secure radio transmission systems has allowed
railways to develop more cost effective signalling. In rural areas of the
UK, where long sections of single line require token block operation, a
system for centralised control, using modern computer technology, was
adopted. It is known as Radio Electronic Token Block (RETB).
At a number of
locations in the UK, this system (shown in the diagram, left) has been in
operation for over 10 years and allows one signalman to control several
single line sections between passing loops. One installation in Scotland
controls over 100 miles of railway.
Each train operating over
the single line is equipped with a special speech and data radio
transmitter/receiver with a unique identity. At the start of the single
line, the driver stops and calls the control centre for authority to enter
the section. If the line is clear, the signalman in the control centre
transmits a coded "electronic token" data message which is received by the
train and then shows the authority for that section on a cab display. The
driver will then call for confirmation that he can enter the section.
Once in the single line section, he will advise the control centre that he
has cleared the loop track. A clearance marker board is specially
provided to help him. When he has reached the end of the single line
section, the driver calls the control centre again and offers to give up
the token. After a "handshake" procedure by the control centre, he sends
the token back by radio data transmission to release the section.
The signalman is provided
with a computer controlled radio system which allocates the coded tokens
to each section and prevents more than one token being issued for an
occupied section. It also receives the tokens sent back by each train as
it reaches the end of the single line section. At the exits of the single
line sections, the points are permanently set in the direction of normal
running and are "trailable" for trains entering the section, i.e. they
allow a train to pass through at reduced speed using the wheel flanges to
move the point (switch) blades aside reset to the normal position.
A "Distant Board" complete
with AWS ramp, warns the driver that he must slow down for the movement
over the points leaving the single line. The Points Indicator shows the
position of the points. A "Stop Board" at the end of the passing loop
warns the driver to stop and ask for permission to enter the next single
line section. The "Loop Clear" board shows when the rear of the train is
clear of the points.
Tyer's Key-Token instrument
This system is commonly
found on modern narrow gauge railways such as the Festiniog.
Token apparatus was
pioneered from 1870 onwards by Tyer and Company Ltd., the early tokens
taking the form of discs or tablets. Key token apparatus was first
introduced in 1912 and with the greatly increased flexibility together
with economy the system was widely adopted on single line railways all
over the world.
Development of the instrument since the earliest days has been continuous
and the latest instruments have many novel features and yet retain the
component reliability which has been a feature of this design since its
inception. Full use is made of die cast light alloys, thermo-plastic
mouldings and rust-resisting alloy steels. Complete interchangability of
component parts is ensured by extensive tooling and quality control
Paints and plating finishes are of the highest quality with the object of
ensuring long life with the minimum of maintenance in the severest of
The No.12 Key Token Instrument is a multi-purpose unit, the basic design
being common to all applications. As the requirements for each application
varies i.e. length and impedance of electrical line, type of operating
function, accessories required etc., a separate design is produced to suit
the individual application.
It has long been accepted that the Key Token system provides the simplest
and safest means of operating trains over a single line from one block
post to another. The acceptance and retention of the token for that block
section provides the driver with authority to occupy the line and only
simple forms of signalling are necessary to ensure compliance with
Operating Regulations. The token may also be used for such supplementary
functions as the release of points for the occupation of an intermediate
The first requirement of a token system is that extraction of a token from
either end of a block section shall require the co-operation of both
signalmen for that section and that it shall be impossible for a second
token to be obtained (except where permissive working is in operation)
until the token, already extracted, has been replaced in one or other of
the section instruments.
The instrument is extremely simple to operate, and easy to maintain. It is
absolutely foolproof, and no tampering can take place.
The instrument is neat and compact. It has only one moving part, viz., an
electrically controlled rotary commutator directly operated by the key
tokens. A key token can be restored to the instrument from which it was
withdrawn in the event of a train being cancelled, or after having been
used for shunting purposes only a small amount of battery power is
required. No permanent currents are necessary. A minimum of working parts
and in consequence, a minimum amount of maintenance.
Further accessories which are available include:
a) The Key Token Balancer - a detachable unit which permits for the safe
and efficient transfer of key tokens between instruments when out of
balance working occurs. This situation occurs particularly when auxiliary
instruments are employed.
b) The Key Token Stand - a ventilated metal cupboard onto which the
instrument is placed which also provides space for the storage of the
batteries which can be supplied as necessary.
c) Hand Generators