GB2306242A - Traffic control sign - Google Patents

Abstract

A traffic control sign is described which is capable of displaying an image of an arrow symbol to indicate to other road users the direction in which they should pass. The sign, which is adapted to be mounted on a vehicle, comprises first and second arrays of discrete light sources (6 Figure 1) which are arranged to display a respective arrow symbol (7) and (8) and, optionally, a circular ring (9). Each array of discrete light sources comprises the free ends of each of a plurality (21, 22 and 23, 24) of optical fibres (17), the other respective ends of which are located adjacent to a respective lamp unit (20 L , 20 R ). Switching means (25) are provided for switching one or other of the lamp units (20 L , 20 R ) to an illuminated condition. The sign may also include an optical fibre running from each lamp unit to the cab of the vehicle to indicate which unit is operative. Means may be incorporated in the sign so that in operation, the sign flashes. A detector of ambient light levels may be included in the sign so that the brightness of the displayed images may be adjusted in response to measured ambient light levels.

Description

TRAFFIC CONTROL SIGN This invention relates to a traffic control sign and, in particular, to a sign which is mounted on the rear of a road or motorway maintenance vehicle, the sign being capable of displaying an image of an arrow symbol to indicate to road users following the vehicle the direction in which they should move to pass the vehicle.

It is known when carrying out road maintenance operations, such as for example surveying the road surface for damage, cutting grass verges or hedges at the edge of the road and other road repair operations, to use a vehicle having a traffic control sign mounted on the rear to indicate to other road users the direction in which they should move to pass the vehicle. Such signs are of a passive nature and are formed from retro-reflective materials. One example comprises a square plate having a circular disc pivotally mounted to the plate. The disc has an arrow symbol formed on the surface. Rotation of the disc enables the sign to display a leftward or rightward pointing arrow.

Despite the highly reflective nature of these signs it is found that some road users do not see them and collide with the vehicle. To alert road users to the sign it is known to provide flashing amber lamps around the sign. However, despite the proliferation of warning devices, a large number of accidents involving such vehicles still occur. It has been estimated that vehicles of this type typically have an expected operating life of a few months before they are likely to be struck by another vehicle.

Despite continued efforts over many years to make such signs more readily visible and thereby reduce the likelihood of accidents occurring, attention has also been focused towards reducing the seriousness of such accidents when they do occur. To reduce the likelihood of serious, or even fatal, injury to other road users or to the operator of the vehicle, it is known to fit a crash cushion to the rear of the vehicle to absorb the impact of another vehicle during a collision.

Since the crash cushion must be capable of withstanding an impact from a vehicle which may be larger than the maintenance vehicle, this results in the crash cushion being of considerable size and prohibitively expensive. Often the crash cushion is pivotally mounted to the rear of the vehicle so that it can be raised when it is not in use. Whilst the crash cushion helps to lessen the seriousness of injury in the event of an accident, it does nothing to lessen the chance of an accident occurring in the first instance.

The likelihood of accidents arising is further compounded when it is required to change the direction in which the arrow points since by necessity the vehicle must stop as the driver or other operator goes to the rear of the vehicle to rotate the arrow to the required direction and secure it in position. Since this is often done in a busy motorway environment the likelihood of an accident occurring is extremely high. To prevent other road users being confused during the operation to change the direction in which the arrow points, it has been known to raise the crash cushion to obscure the sign during the changeover operation. Regrettably such an operation has resulted in an accident involving multiple fatalities.

The present invention addresses the problem of making a traffic control sign which is more visible and which can be changed from one state to another without the need to stop the vehicle. It is an object of the present invention to provide a traffic control sign which, in part at least, overcomes the problems associated with the known signs.

According to the invention there is provided a traffic control sign which is adapted to be mounted on a vehicle, the sign comprising: first and second arrays of discrete light sources, each array being arranged to display a respective arrow symbol, wherein each array of discrete light sources comprises the free ends of each of a plurality of optical fibres, the other respective ends of which are located adjacent to a respective lamp unit, and switching means for switching one or other of the lamp units to an illuminated condition. Preferably, each light source further includes a lens for collimating light emitted from the free end of the optical fibre.

To further increase its visual impact, the sign preferably comprises means for modulating the electrical power provided to the lamp units such that, in operation, the sign flashes, thereby alerting other road users to the presence of the sign.

Since each arrow symbol is constituted by an array of discrete light sources and is of an active nature, the display is highly visible compared to known passive displays. Advantageously the switching means are mounted remotely from the sign and preferably in the cab of the vehicle, enabling the sign to be switched so as to display the first or second arrow symbol without having to stop the vehicle.

In a preferred arrangement the sign further comprises an optical fibre running from each lamp unit to the cab of the vehicle to indicate which lamp unit is currently operative and hence which arrow symbol the sign is currently displaying. Since such an arrangement is essentially passive it is virtually failsafe in that, should the optical fibre be damaged, it will alert the operator to a fault even when the sign may still be functioning correctly. In contrast an electronic indication could fail to a state indicating that the sign was still working correctly., when in fact it was not.

Preferably the sign further comprises an array of discrete light sources arranged in a circular ring around the pair of arrow symbols. With such an arrangement it is preferable that alternate light sources in the circular ring are associated with the first lamp unit and the intervening light sources are associated with the second lamp unit, such that no further lamp units are required to operate the sign.

Preferably each lamp unit includes at least two lamps and a beam splitter for coupling light from each of the lamps into all of the optical fibres of a given array. With such an arrangement, should one lamp fail, the sign will continue to operate at a reduced brightness.

Advantageously, each lamp comprises a halogen bulb.

According to a further preferred embodiment of the invention, the lamp units are powered from the electrical system of the vehicle during normal operation and an electrical back-up power supply is provided which automatically cuts in to provide electrical power to the lamp unit if the vehicle's electrical system fails.

Preferably the sign further comprises a light detector for measuring the ambient light level and means for adjusting the electrical power to the lamp units in response to the measured ambient light level. Such an arrangement ensures that the sign can still be read in bright sunlight and prevents the sign dazzling road users during nighttime operation.

An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a representation of a traffic control sign according to the invention; Figure 2 is a cut-away schematic representation of the traffic control sign of Figure 1; Figure 3 is a cross section through an optical fibre lens arrangement; Figure 4 is a schematic representation of a lamp unit of Figure 2; Figure 5(a) is a schematic representation of driver circuitry for operating the sign of Figure 2; and Figure 5(b) is a schematic representation of an electronic warning circuit.

Referring to Figure 1 there is shown a maintenance vehicle 1 with a traffic control sign 2 in accordance with the invention mounted on the rear of the vehicle 1. The traffic control sign 2 is mounted on a support plate 3 which is pivotally attached to a support frame 4. The support frame 4 is secured to the vehicle by means of suitable fastenings which enable the support plate 3 and sign 2 to be folded flat with the vehicle during transportation.

A crash cushion (not shown) can be mounted to the rear of the vehicle 1 by means of brackets 5. The sign 2 includes two arrays of discrete light sources 6, each of which is arranged to produce a respective arrow symbol - a first arrow symbol 7 which points in a left, downward direction, and a second arrow symbol 8 (not shown) which points in a right, downward direction 8. Encircling the arrow symbols 7 and 8 is an array of discrete light sources which are arranged to form a circular ring 9. Four amber flashing lamps 10 are provided at the corners of the support plate 3. The surface of the sign 2 enclosed by the circular ring 9 has a retro-reflective surface which has a viewing angle of a fraction of a degree. Such a surface prevents glare from the sign that might otherwise result from stray light such as, for example, strong sunlight, reflecting off the surface of the sign.

Referring to Figure 2, the sign 2 comprises a plate 11 in which are formed a plurality of apertures 12 each for receiving a discrete light source. The apertures 12 are arranged so as to form the circular ring 9 and the two arrow symbols 7 and 8.

Each discrete light source comprises an optical fibre lens arrangement as shown in Figure 3.

The optical fibre lens arrangement comprises a generally cylindrical hollow body 13, a first end of which forms an interference fit in the aperture 12. A shoulder portion 14 which extends radially from the body 13 abuts with the inside surface of the plate 11 when the body 13 is correctly located in the aperture 12. Disposed axially in the body 13 there is a frusto conical lens 15 which has a convex base 16 for emitting light therefrom. The tapered end of the lens 15 abuts with the end of an optical fibre 17. Each optical fibre 17 comprises a number, typically two hundred, of individual fibres 501lem in diameter which are enclosed in a protective sheath. The ends of the optical fibres are polished to ensure efficient optical coupling to the lens 15.The optical fibre 17 is held within the body 13 by a clamping member 18 which locates in a bore 19 formed in the body 13. The lens 15 is arranged to produce a divergent beam of light within an angle of +7 about its central axis, such that each optical fibre lens arrangement has a viewing angle of 14 .

Referring to Figure 2, the other end of each optical fibre 17 is connected to an associated lamp unit 20. Two lamp units 20 are provided; a first lamp unit 20,for the arrow symbol 7 and a second lamp unit 20R for the arrow symbol 8. The optical fibres 17 are grouped in four bundles 21 to 24, two bundles being illuminated by an associated lamp unit 20. In the embodiment illustrated bundles 21 and 22 are associated with arrow symbol 7 whilst bundles 23 and 24 are associated with arrow symbol 8.The light sources 6 in the circular ring 9 are arranged such that alternative light sources are connected to the first lamp unit 20L whilst the intervening light sources are connected to the second lamp unit 20 R In operation, illumination of the lamp unit 20,produces the leftward pointing arrow symbol 7 enclosed by circular ring 9 in which alternate light sources in the ring are illuminated, whilst operation of the lamp unit 20R illuminates the rightward pointing arrow symbol 8 enclosed by circular ring 9 in which the intervening light sources are operative. Selection of the lamp units 20L, 20R is by means of a switch 25 which is preferably located in the cab of the vehicle 1.

A schematic representation of the lamp unit 20L is shown in Figure 4, though it will be appreciated that lamp unit 20R is identical. The lamp unit 20L comprises a box 26 having two ports 27 and 28 for receiving the optical fibre bundles 21 and 22 respectively. Two halogen lamps 29 and 30 located in apertures 31 and 32, formed in the side of the box 26, are arranged to direct light towards the ends of the optical fibre bundles 21 and 22, respectively. A beam splitter 33 disposed at 45" to the lamps 29 and 30 is arranged to split the light from each lamp 29 and 30 so as to illuminate the ends of both of the bundles 21 and 22. In operation both lamps 29 and 30 are operated simultaneously such that the light from the lamps 29 & 30 are shared between the optical bundles 21 and 22.

Simultaneous operation of both of the lamps 29 and 30 is advantageous for a number of reasons. Firstly, the light output of two bulbs is coupled into each optical fibre 17 which produces a much brighter intensity sign. Secondly, as more light is coupled into each optical fibre 17, each lamp can be operated at a lower voltage which increases the operating life of the lamps. Thirdly, in the event that one lamp should fail, each of the optical fibres 17 will still receive light from the other lamp although at half the intensity and the sign will continue to display the correct arrow symbol but with a reduced intensity. A sign made in accordance with the present invention has been found to work successfully for viewing distances of up to 400 metres.

Referring to Figure 5(a) in normal operation the lamp units 20Land 2OR are driven from the vehicle's electrical system 37. However, in the event that the electrical system 37 should fail, a back-up battery 38 is automatically switched into operation by means of a relay 39. Since the vehicle's electrical supply can be either 12 or 24 volts, a voltage converter 40 is provided to ensure that the supply voltage Vb" is held within a selected operating range.The output of the voltage converter is connected to a driver circuit 41 which produces the drive voltage VdrjVe supplied to the lamp units 20L and 2OR. A modulating circuit 42 is provided to modulate the drive voltage Vd,*,e such that the sign will flash 'on' and 'off' during operation to further increase the visual impact of the sign. A photodetector 43 mounted on the face of the sign 2 is used to measure the ambient light level. The driver circuit 41 adjusts the drive voltage Vd,ive in response to the ambient light level to adjust the intensity of the sign. Such a feature is particularly advantageous for ensuring that the sign has maximum impact irrespective of whether it is being operated during daylight or nighttime conditions.

From each of the lamp units 20L and 2OR a respective optical fibre 34L 34R is run to the cab of the vehicle. The end of each of the fibres 34L and 34,its terminated with a suitable lens arrangement to provide a visual indication to the operator as to which lamp unit is currently operative. A particular advantage of such an arrangement is that, being of an essentially passive nature, it cannot falsely indicate that a lamp unit is operative if, in fact, it has failed.

In addition, if the optical fibre 34 is damaged the operator will be alerted to the problem even though the sign is still functioning correctly.

A schematic representation of an electronic warning circuit 44 is illustrated in Figure 5(b) and is operative to provide an audible warning to the operator if a fault condition arises. In the event that one of the lamps 29 or 30 in a lamp unit fails in an open circuit condition, an intermittent audible warning 45 is produced. The failure of a bulb 29 or 30 is detected by either current ii, i2 through the first or second lamp falling below a threshold value. In the event that both bulbs 29 and 30 in a lamp unit fail, a continuous audible warning 46 is produced. The failure of both lamps is detected by both currents i 1and i 2falling below a selected value.

A further optical fibre 35D 35R is connected to each lamp unit 20, 20R and is coupled to a respective photodetector 36L and 36R The photodetectors 36L, 36R produce electrical signals Loptica and Optical which indicate whether a lamp unit 20L' 20R is producing light. In the event that either of the signals Optical or Roptlcal falls below a threshold value when the lamp unit should be operative, a continuous alarm 46 is sounded to alert the operator to the problem.

If the vehicle's electrical system 37 fails the supply voltage Vbat falls below a threshold value and the back-up supply 38 switches in automatically. In addition a continuous alarm is sounded to alert the operator of the fault condition.

It will be appreciated by those skilled in the art that modifications of the embodiment illustrated can be made within the scope of the present invention. For example whilst in the embodiment described the optical fibre lens arrangement has a viewing angle of 14 , viewing angles in the range 10 to 150 can be used depending upon the particular application and the required viewing distance. The switch 25 could for example comprise a relay located in the sign which is operated by mechanical switch located in the cab of the vehicle. The electronic warning circuit 44 whilst illustrated as discrete logic circuit could be implemented using a microprocessor or analogue circuitry.

Claims (14)

1. A traffic control sign which is adapted to be mounted on a vehicle, the sign comprising: first and second arrays of discrete light sources, each array being arranged to display a respective arrow symbol, wherein each array of discrete light sources comprises the free ends of each of a plurality of optical fibres, the other respective ends of which are located adjacent to a respective lamp unit, and switching means for switching one or other of the lamp units to an illuminated condition.

2. A traffic control sign, according to Claim 1, wherein each light source further includes a lens for collimating light emitted from the free end of the optical fibre.

3. A traffic control sign, according to Claim 2, wherein the viewing angle of each light source has a value in a range of 10 to 15 .

4. A traffic control sign, according to Claim 1, 2 or 3, further comprising an optical fibre running from each lamp unit to the cab of the vehicle to indicate which lamp unit is currently operative.

5. A traffic control sign, according to any preceding claim, wherein each lamp unit includes at least two lamps and a beam splitter for coupling light from each of the lamps into all of the optical fibres of a given array.

6. A traffic control sign, according to any preceding claim, wherein each lamp comprises a halogen bulb.

7. A traffic control sign, according to any preceding claim, further comprising an array of discrete light sources arranged in a circular ring around the pair of arrow symbols.

8. A traffic control sign, according to Claim 7, wherein alternate light sources in the circular ring are associated with the first lamp unit and the intervening light sources are associated with the second lamp unit.

9. A traffic control sign, according to any preceding claim, wherein the lamp units are powered from the electrical system of the vehicle during normal operation, and further comprising an electrical back-up power supply which automatically cuts in to provide electrical power to the lamp units if the vehicle's electrical system fails.

10. A traffic control sign, according to any preceding claim, in which the switching means are mounted remotely from the sign.

11. A traffic control sign, according to any preceding claim, further comprising means for modulating the electrical power provided to the lamp units such that, in operation, the sign flashes.

12. A traffic control sign, according to any preceding claim, further comprising a light detector for measuring the ambient light level and means for adjusting the electrical power to the lamp units in response to the measured ambient light level.

13. A traffic control sign substantially as described by way of reference to any of Figures 1, 2, 3, 4 or 5 of the accompanying drawings.

14. A vehicle incorporating a traffic control sign in accordance with any of claims 1 to 13.

14. A vehicle incorporating a display in accordance with any of claims 1 to 13.

Amendments to the claims have been filed as follows

1. A traffic control sign which is adapted to be mounted on a vehicle, the sign comprising: first and second arrays of discrete light sources, each array being arranged to display a respective arrow symbol, wherein each array of discrete light sources comprises the free ends of each of a plurality of optical fibres, the other respective ends of which are located adjacent to a respective lamp unit, and switching means for switching one or other of the lamp units to an illuminated condition.

2. A traffic control sign, according to Claim 1, wherein each light source further includes a lens for collimating light emitted from the free end of the optical fibre.

3. A traffic control sign, according to Claim 2, wherein the viewing angle of each light source has a value in a range of 10 to 15".

4. A traffic control sign, according to Claim 1, 2 or 3, further comprising an optical fibre running from each lamp unit to the cab of the vehicle to indicate which lamp unit is currently operative.

5. A traffic control sign, according to any preceding claim, wherein each lamp unit includes at least two lamps and a beam splitter for coupling light from each of the lamps into all of the optical fibres of a given array.

6. A traffic control sign, according to any preceding claim, wherein each lamp comprises a halogen bulb.

7. A traffic control sign, according to any preceding claim, further comprising an array of discrete light sources arranged in a circular ring around the pair of arrow symbols.

8. A traffic control sign, according to Claim 7, wherein alternate light sources in the circular ring are associated with the first lamp unit and the intervening light sources are associated with the second lamp unit.

9. A traffic control sign, according to any preceding claim, wherein the lamp units are powered from the electrical system of the vehicle during normal operation, and further comprising an electrical back-up power supply which automatically cuts in to provide electrical power to the lamp units if the vehicle's electrical system fails.

10. A traffic control sign, according to any preceding claim, in which the switching means are mounted remotely from the sign.

11. A traffic control sign, according to any preceding claim, further comprising means for modulating the electrical power provided to the lamp units such that, in operation, the sign flashes.

12. A traffic control sign, according to any preceding claim, further comprising a light detector for measuring the ambient light level and means for adjusting the electrical power to the lamp units in response to the measured ambient light level.

13. A traffic control sign substantially as described by way of reference to any of Figures 1, 2, 3, 4 or 5 of the accompanying drawings.