GB2244836A - Traffic light system - Google Patents

Abstract

In a traffic light warning system which has a normal signal head having lights 3 which in operation pass through the traditional sequence of colours, the head incorporates an additional warning light 4 as a permanent feature which is brought into operation when failure of one or more of the normal lights 3 is detected. <IMAGE>

Description

TRAFFIC LIGHT SYSTEM The present invention concerns traffic lights. A number of the faults which occur at lamprontrolled junctions result in all signal lamps being switched off until the fault is rectified.

For example, poor neutral connections, which would lead to half-glowing signals on many aspects, are now detected by green voltage monitoring circuits within the controller.

Similarly, increasing use of part-time signalling, particularly at signal controlled roundabouts and trunk road slipways, and the use of audible or tactile indicators, demand the use of red-lanp monitoring to ensure safety in these situations.

Furthermore it is likely that red-lamp monitoring will become a standard practice at all sites in the near future. While this will lead to an overall increase in safety it will mean that, for a small proportion of the time, some aspects having failed red lamps will cause the whole junction to be shut down because ultimate safety cannot be assured.

Recent legislation will require many current maintenance practises to be reviewed. It is'likely that a particularly strong recommendation will be given that working on 'live' equipment (live working) should be employed only where it is absolutely necessary.

Thus live working for bulb changing, securing terminations and general maintenance will need careful review and avoidance where possible. This will create a dilemma for local traffic management authorities and maintenance organisations, since a balanced decision will have to be made between the dangers of live working and traffic control dangers arising from switching signals off.

All of the foregoing considerations will lead to signals generally being turned off, either for safety or maintenance reasons, more frequently than in the past. Thus, if real safety is to be achieved, the road users must be alerted to the fact that the traffic-control signals are temporarily out of action and that additional care must be exercised. The present invention is concerned with the alleviation of this proLlem.

Accordingly the present invention comprises a traffic warning system having a normal signal head having lights which in operation pass through a sequence of colours, and an additional warning light which is brought into operation when failure of one or more of the normal signal head lights is detected.

Preferably the warning light is associated with a voltage detector connected to either the existing signal supply line or to the existing signal aspects.

The power supply for the warning light may be a battery and the battery may have associated charging means which are connected to the power supply for the normal lights.

In order that the present invention may be more readily understood an embodiment thereof will now be described by way of example and with reference to the accompanying drawings, in which, Figure 7A shows an existing signal head, Figure IS shows a signal head according to the present invention, Figure 3 is a block diagram of a power unit for a signal head of the kind shown in Figure 18, and Figure 4 is a block diagram of a back-up supply.

Referring. now to Figure 1 of the accompanying drawings this shows a standard traffic light 1 mounted on a pole 2 and having the usual red, amber and green lights indicated at 3.

It is already known to provide an arrangement whereby the central amber light flashes should a fault be detected. However this arrangement cannot cope with the situation where power has to be turned off leaving all lights extinguished.

Accordingly when there has either been a complete breakdown at a traffic light junction or it has been necessary to switch off all power for, for example, maintenance purposes. In order to give an indication that there are no lights functioning it has been known to strap one or more flashing amber lights to the poles at the junction. This solution has a number of drawbacks amongst which is the time necessary to mount the additional flashing lights and the fact that the lights are usually strapped below the normal light, thus reducing the impact and visibility of the warning.

Referring now to Figure lB of the drawings this shows a signal head according to the present invention. In this Figure integers which are identical to those of the Figure 1A embodiment have been given the same reference numerals.

In Figure 1B it can be seen that a fourth light has been permanently mounted at the peak of the signal head. This light 4 is amber and has its own independent power supply. This power supply is shown in Figure 2 of the drawings. It comprises a low voltage 48V supply 5, a lamp voltage detector and a maintenance socket outlet 7. This is to replace the one utilised by the unit.

The lamp voltage detector 6 is connected to the existing signal supply line 8 and controls a switch 9 so that on detection of a reduction in voltage in the line 8 the switch 9 is closed and power supplied to the or each of the amber flash lights permanently in position on the signal heads of the road junction in question.

Because of the use of a voltage detector in conjunction with the existing signal line there is no real need to provide an additional switch for the amber flashing lights. Either a failure in the existing line or the deliberate disconnection of power will bring the amber flashing lights into operation.

The unit shown in Figure 2 is self-resetting in that when the main supply voltage returns the switch 9 is opened and is also protected against the appearance of high voltages at the output terminal. Throughout a junction the supply to the amber flashing lights can be connected using spare cores within the existing signal cabling.

There will also be situations where the additional amber flashing lights are required to be independent of the mains power supply, or where spare cores are not available at a particular junction. Accordingly the gaining unit will be powered from a rechargeable battery. During normal signal operation the battery will be recharged from a trickle charger powered from the signal aspect supply. This is the arrangement shown in Figure 3 of the accompanying drawings.

Thus in Figure 3 the detector 6 is connected to the three existing signal aspects R, A and S by zener diodes 10 which are also connected to a switching regulator/charger 11 capable of providing a trickle charge to a battery 12 the output of which can be connected by switch 9 to amber warning light 13.

In normal power supplies for traffic junctions the mains voltage is taken to the head of the lights and is transformed down for distribution to the bulbs. The failure detectors shown in Figures 2 and 3 can be either before or after this transformer. It is advantageous if the failure detector can operate in a low power mode as it also has to detect when power is reinstated. Another advantage of the system just described is that if one pole at a junction fails due to a cabling fault it can be switched to give a flashing amber warning without the operation of the remaining lights at the junction being affected.

Claims (5)

1. A traffic warning system having a normal signal head having lights which in operation pass through a sequence of colours, and an additional warning light which is brought into operation when failure of one or more of the normal signal head lights is detected.

2. A traffic warning system as claimed in Claim 1 wherein the warning light is associated with a voltage detector connected to either the existing signal supply line or to the existing signal aspects.

3. A traffic warning system as claimed in either Claim 1 or Claim 2 wherein the power supply for the warning light is a battery.

4. A traffic warning system as claimed in Claim 3 wherein the battery is connected to charging means which are connected to the power supply for the normal lights.

5. A traffic warning system substantially as hereinbefore described with reference to the accompanying drawings.