GB2320601A

GB2320601A - Safety system for railways

Info

Publication number: GB2320601A
Application number: GB9625093A
Authority: GB
Inventors: David Michael Dore; Peter Robert Frost
Original assignee: INTELLIGENT CAB SYSTEMS LIMITE
Current assignee: INTELLIGENT CAB SYSTEMS LIMITE
Priority date: 1996-12-03
Filing date: 1996-12-03
Publication date: 1998-06-24
Anticipated expiration: 2016-12-03
Also published as: GB9625093D0; GB2320601B

Abstract

A method and safety system are described for monitoring the alertness of the driver of a train. A button is provided in the train cab to be manually operated by the driver on noting that the next track side signal is displaying a non-clear aspect. Sensing means, for example as used in convention a1 AWS systems, are provided for producing as the train approaches each track side signal an electrical signal indicative of the status of the track side signal. The brakes of the train are automatically applied whenever an electrical signal from the sensing means indicative of a non-clear aspect is produced before the button is operated by the driver.

Description

SAFETY SYSTEM FOR RAILWAYS The present invention relates to a safety system for use in the cab of a train.

It is conventional to provide signals by a railway track to indicate to the train driver the status of the section of the line that lies ahead. The signals are similar to road side traffic lights except that, in place of a single amber light, railway signals have two yellow lights. A green aspect indicates that the line ahead is clear, a double yellow aspect requires the driver to slow down and proceed with caution, a single yellow aspect indicates that the driver should be prepared to stop the train at the next signal. A red aspect indicates that the section of line ahead is obstructed and the driver must stop the train.

It is also conventional to provide within the cab of a train an automatic warning system (AWS) to make sure that the train driver does not disregard a track side signal.

The known AWS system consists of a first component that is located on the track and a second component located on the train that interact magnetically with one another to issue an audible warning within the driver's cab.

The stationary component installed by the track a short distance in rear of the signal consists of two magnets. The first magnet is a permanent magnetic with an upwards facing south pole and the second is an electromagnet with an upwardly facing north pole. The electromagnet is only energised when the signal is clear and shows a green aspect.

The moving component on the train comprises a toggle switch that is moved to a set position when it passes over the south pole and returns to the reset position if it passes shortly thereafter over a north pole. If the toggle switch is rapidly set and reset, a circuit connected to it sounds a bell to indicate to the driver that the section of line ahead is clear and that he can expect to see a green light at the coming signal. If however the toggle switch is set by passing over the permanent south pole but not reset by seeing a north pole, in other words if the signal is displaying other than a green aspect, then a warning horn is set off in the cab and the driver is required to press a reset button, to confirm that he is aware that the track side signal is not green. If the driver presses the button within a predetermined time, toggle switch is reset and the warning horn is switched off. If however the driver fails to acknowledge the warning given by the horn, then the brakes of the train are applied for a minimum of seven seconds or until the train speeds drops to below 6kph, after which the driver can regain control by pressing the AWS reset button.

A still further visual warning is provided in the cab by an electromechanical visual indicator which displays an all black when the track is clear and displays a yellow and black face as a caution reminder if the track side signal is not clear.

A problem with known AWS systems is driver error.

Because the warning horn is an irritating sound that occurs rather frequently under some driving conditions, train drivers tend to drive with one hand on the AWS button and to activate it instinctively every time the horn is heard.

Because of this instinctive operation of the AWS reset button, it cannot be assumed that the driver is concentrating fully and that he is aware that the track ahead is not clear when he clears the warning signal.

The present invention seeks to provide a modified warning system that reduces driver error and avoids the possibility of warning signals being disregarded on account of habit.

According to one aspect of the present invention, there is provided a method of monitoring the alertness of the driver of a train, which method comprises providing in the train cab a button to be manually operated by the driver on noting that the next track side signal is displaying a nonclear aspect, providing on the train sensing means for producing as the train approaches each track side signal an electrical signal indicative of the status of the track side signal, and automatically applying the brakes of the train when an electrical signal from the sensing means indicative of a non-clear aspect is produced before the button is operated by the driver.

The present invention differs from the prior art essentially in that it provides a proactive system rather than a reactive system. The driver is required to respond to the visual track side signal before reaching the point on the track at which an AWS signal would normally be produced.

On seeing the track side signal, he should at once operate the button to set a flag that indicates that he is aware that the signal being approached is indicating a cautionary (red, single yellow or double yellow) aspect. If the automatic signal sensor confirms that the signal is displaying a non-clear aspect, then the signal produced by the automatic signal sensor merely resets the flag and the train is left under the control of the train driver, who has already demonstrated his alertness. If on the other hand the driver is not alert and the automatic signal sensor detects that the signal being approached is displaying a non-clear aspect before the driver has pressed the button, then the brakes are applied immediately without further warning being given to the driver.

According to a second aspect of the present invention, there is provided a safety system for use on board a train, the system comprising a button to be manually operated by the driver on noting that the next track side signal is displaying a non-clear aspect, sensing means for producing as the train approaches each track side signal an electrical signal indicative of the status of the track side signal, and means for automatically applying the brakes of the train when an electrical signal from the sensing means indicative of a non-clear aspect is produced before the button is operated by the driver.

The invention can use the same track side equipment as is currently in use for conventional AWS systems to detect the status of the signal being approached. Essentially, a permanent magnet and an electromagnet are mounted in rear of each signal, the electromagnet magnet being switched on only when the signal ahead is displaying a clear aspect. However, instead of the state of the electromagnet being used to generate a warning that the driver must acknowledge, it is used in the present invention to operate the brakes if the driver has not displayed his awareness by anticipating the warning and operating the button ahead of reaching the signal.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic representation of a track installation and a train mounted receiver, Figure 2a is a flow chart showing the operation of a conventional AWS system when a clear signal is approached, Figure 2b is a flow chart showing the operation of a conventional AWS system when a caution or danger signal is approached, and Figure 3 is a similar flow chart to Figure 2a showing the operation of a proactive safety system of the invention when approaching a signal displaying a caution or danger aspect.

In Figure 1 there is shown schematically the hardware used in conventional AWS system. Two hundred metres before reaching a signal 10, a train carrying a receiver armature 14 passes over a ramp 12 having two magnets 12a and 12b.

The magnet 12a is a permanent magnet with an upwardly facing south pole whereas the magnet 12b is an electromagnet with an upwardly facing north pole that is only energised when the signal 10 is displaying a green light (clear aspect).

The operation of both a conventional system and a system of the present invention when a clear aspect is displayed is essentially the same and is represented by the flow chart in of Figure 2a. As indicated in the box 21, as the signal is clear, no action is required by the driver.

Because the electromagnet 12b is on, the armature 14 in the train that acts as a means for automatically sensing the status of the signal 10, brief toggles between states as the train passes in the direction represented by the arrow in Figure 1 over the ramp 12. As described in box 22, this brief toggling of the armature results in the sounding an "all clear" bell and in the setting of a visual indicator in the cab to all black.

The visual indicator in the prior art is a device resembling a "hit and miss" ventilator aperture. A black face has radial slots through which portions of a plate lying behind the face can be seen. The plate carries yellow and black radial markings. Depending on the position of the plate, the visual indicator can either display a totally black appearance or a black and yellow appearance. The purpose of the visual indicator is to act as a reminder of the status of the last signal that was passed. In the preferred embodiment of the present invention, the visual indicator is an electronic device.

The course of events when the signal 10 displays a red light (danger), two yellow lights (caution), or a single yellow light (advanced warning) is shown in Figure 2b for a conventional AWS system.

In this case, only the south permanent magnet in the ramp 12 generates a magnetic field because the magnet 12b is not energised (block 25). As a result, when the armature 14 passes over the ramp, the train receiver in block 24 transmits the AWS magnet signal to a control unit that immediately sounds a horn and sets the visual indicator to all black. The driver is expected if alert to respond to the horn sound by depressing an AWS reset button mounted in the cab.

If the AWS button is depressed within three seconds of the armature 14 passing over the ramp 12 (block 26), then warning horn ceases and the visual indicator is changed to black and yellow to act as a reminder (block 28). As the driver is alert, he will adjust the train speed himself as appropriate as indicated in the block 30.

If on the other hand the driver fails to acknowledge the caution and does not press the reset button within three second (block 27) then the warning horn will sound continuously and the train brakes will be applied fully while the visual indicator remains at black (block 29).

Only after a predetermined period (usually seven seconds) has elapsed or a predetermined drop in speed (usually to below 6kph) has been achieved can the driver regain control of the train by depressing the AWS reset button (block 31).

As earlier mentioned, the instinctive depression of the AWS button can result in a warning signal being disregarded by a driver, in that he can acknowledge the horn signal but not act upon it. In other words, it has been assumed that the action in block 30 of Figure 2b is an inevitable consequence of the action taken in block 26 when in practice this is not necessarily the case when the driver acts outs of reflex rather than conscious decision.

The invention overcomes this problem by adopting a proactive rather than a reactive approach for which reason it will hereinafter be termed a PAWS (proactive automatic warning system). The hardware in use is very similar to that used by the conventional AWS system described above, the physical differences residing only on the wiring of the various relays that constitute the control unit to which the armature 14 is connected. Indeed, it is a particular advantage of the present invention that it only requires a modification to the control unit and does not call for any change in the track side equipment nor in the wiring of the entire cab. The control unit in the present invention, in the same was as the control unit of a conventional AWS system, is connected to a button (which now acts as a PAWS acknowledgement button), to the visual indicator and to the brakes and it differs only in the sequence of events that occur when the signal 10 is displaying a non-clear aspect.

For these reasons, it is believed that the construction of the control unit will be clear to the person skilled in the art from the following description of its function and that there is no need to describe in detail the wiring of the various relays that constitute the control circuit.

In the present invention, on approaching (block 40) a signal displaying a non-clear aspect, the driver must depress the PAWS button (block 42) and this will result in a visual indication or a soft tone (not a horn) being sounded in the cab. As the train passes over the ramp 12, the sensing in the block 44 of the state of the magnet 12b in the ramp 12 will switch off the visual indication or the tone and set the visual indicator to black and yellow. The driver, not having now acted by reflex or instinct, can be relied upon to adjust the train speed according to the prevailing conditions as indicated in block 46.

Should the driver however fail to notice that he is approaching a signal 10 displaying a non-clear aspect, as indicated in block 43, then no tone will sound and nothing will occur until the train passes over the ramp 12 in block 45. At this time, without further warning, the train brakes are applied and a horn is sounded to warn the driver that he has failed to notice a warning signal. The driver cannot regain control of the train until it has dropped below a predetermined speed or until a fixed period of brake application has lapsed, whichever is the earlier. The visual indicator is now set to indicate a flashing yellow and black signal until the next signal is approached to indicate that brake intervention has take place (block 47).

It will be appreciated that various modifications may be made without departing from the scope of the invention as set out in the appended claims. In particular, the described embodiment is intended to make maximum use of equipment already present in convention AWS systems, but for the purposes of the present invention, the manner in which the status of a track side signal is communicated to the control circuit in the train may be varied significantly.

The simple magnets used are preferred because they are proven and operate even in difficult environmental conditions but in principle they can be replaced by any other suitable system, for example a short range radio system.

Claims

1. A method of monitoring the alertness of the driver of a train, which method comprises providing in the train cab a button to be manually operated by the driver on noting that the next track side signal is displaying a non-clear aspect, providing on the train sensing means for producing as the train approaches each track side signal an electrical signal indicative of the status of the track side signal, and automatically applying the brakes of the train when an electrical signal from the sensing means indicative of a non-clear aspect is produced before the button is operated by the driver.

2. A safety system for use on board a train, the system comprising a button to be manually operated by the driver on noting that the next track side signal is displaying a non-clear aspect, sensing means for producing as the train approaches each track side signal an electrical signal indicative of the status of the track side signal, and means for automatically applying the brakes of the train when an electrical signal from the sensing means indicative of a non-clear aspect is produced before the button is operated by the driver.