[0001] This invention relates to a temporary traffic signalling system.

Background to the Invention

[0002] Controlling the flow of traffic through roadworks and other temporary constrictions is typically achieved by means of portable traffic light systems. However, for some short-term works, particularly on busier roads, the delays necessarily included in automatic traffic light systems while they cycle through the separate stages of operation can cause unnecessary congestion, and setting up such systems may be undesirable. In such circumstances, the contractors undertaking the works may be required by the controlling authority to use manually-operated stop-go boards, in the form of a rotatably reversible sign having a red "stop" indication on one side and a green "go" indication on the other. The operators can react more quickly to changing traffic conditions, thereby minimising disruption. [0003] The main disadvantage of traditional stop-go boards is that, since they are typically manually operated, for most situations at least two operators are required and more are required at a junction where more than two directions are involved. This increases the cost of the works significantly, and is dependent on the reliability of the people employed to do the job. In an attempt to reduce the number of operators required, a mechanised version of the stop-go board has been developed, with a stop-go board carried on a vertical shaft mounted in a rotary mechanism that can turn the shaft through 180 degrees on command from a remotely positioned operator. While this reduces the personnel requirement, the rotation of the signs is sometimes unreliable. Since the rotation of the signs requires a motor drive, battery life tends to be poor. Additionally, there is a risk, as with the manually operated version, that the motorists, seeing the far sign rotated to stop the advancing traffic, might wrongly believe that the now-visible "go" side of the sign is inviting him or her to proceed before the traffic has cleared and the near sign is rotated. Mechanised stop-go boards can also only be used as a pair, thereby precluding use for junctions with multiple directions to be controlled. [0004] A further disadvantage with conventional stop-go boards is that they require the provision of lights to illuminate the boards at night. This not only increases costs, but may also expose the operators to the risk of being struck by passing vehicles because they can be much less visible than the illuminated board.

[0005] The present invention seeks to provide a more reliable and cost-effective temporary signalling system.

Summary of the Invention

[0006] According to the invention, there is provided a temporary traffic signal- ling system, comprising at least two signalling light display units, each having a wireless receiver connected to a display controller, and a system controller having a wireless transmitter and manually operable controls selectively operable to transmit a control signal to change the state of a selected one of the display units from displaying a stop light signal to displaying a go light signal, characterised in that each display controller is configured to display a stop light signal unless a control signal for the signalling light display unit is being received and in that the system controller comprises a reset button, operation of which causes termination of signal transmission by the wireless transmitter, and is further configured to prevent a user from causing a further selective control signal to be transmitted until the reset button has been operated.

[0007] Preferably, each light display unit comprises a wireless transmitter controlled by the display controller to transmit a confirmation signal confirming display of the go light signal in response to receipt of the control signal, and the system controller includes a wireless receiver to receive the confirmation signal and to activate a visual indicator. Thus, for example, if the display controller may be configured so that the confirmation signal is not transmitted if the display controller detects an error in the operation of the light signals. The system controller is preferably configured to stop transmission of the control signal if the confirmation signal is not received thereby, requiring operation of the reset button by the user. [0008] Each display unit may comprise a phase selector whereby one of a plurality of phases or channels may be selected, and the system controller is configured to transmit the control signal in a selected phase so as to be receivable by the or each display unit selecting that phase. The system controller is prefer- ably configured to transmit a control signal coded to indicate the selected phase and the display controller in each display unit is configured to change the state of the unit in response to receipt of the code.

[0009] Each display unit comprises an array of lights selectively switchable to display indicia indicating the stop signal or the go signal. The array of lights is suitably configured to select different coloured lights for the stop and go signals. The lights in the array may be light-emitting diode devices. It will be appreciated that other forms of display may be usable.

[0010] Advantages of the system of the invention include the fact that one person can control the system (on site) and that person can be safely located away from traffic flows. By using a light-emitting display, it is possible to easily work at night, or in fog.

[0011] Because the display units are directional, the opposing traffic will not see the GO on a distant unit, further contributing to safe operation. The system permits multiphase operation, with one operative controlling a multi-way junction. In addition, pairs or multiples of display units can be operated on the same phase, increasing visibility and again increasing safety.

[0012] The system of the invention can be made very lightweight, with the display units configured to fold when not in use to reduce bulk, and therefore can be readily carried and set up by one person. Brief Description of the Drawings

[0013] In the drawings, which illustrate an exemplary embodiment of the invention:

Figure 1 is a front elevation of a display unit forming part of the system of the invention, displaying a stop signal; Figure 2 is a view corresponding to that of Figure 1 , but displaying the go signal;

Figure 3 is a circuit diagram showing one configuration of the system controller; and

Figure 4 is a circuit diagram for a display controller.

Detailed Description of the Illustrated Embodiment

[0014] Referring to Figures 1 and 2, the display unit comprises a lightweight, preferably foldable screen 1 (in the illustrated embodiment, the screen has three foldable elements 1 a, 1 b and 1 c which are hinged together so that the side ele- ments 1 a and 1 c can be folded on to the centre unit 1 b when not in use, but it will be appreciated that the foldable screen can have a different number of foldable elements and that a single, non-foldable, screen could be employed). On the rear of the centre element is mounted a housing (not shown) for the display controller and a power supply, the housing mounting an external selector switch for selecting the operating phase of the unit, as hereinafter described. The housing may also mount a stand for holding the unit in a suitable position at the roadside with the screen facing oncoming traffic.

[0015] The screen 1 comprises an array of LED devices, suitably with a double outer ring 2 of white LEDs, a main array 3 of 2-state LEDs capable of being switched between a red-emitting state and a green-emitting state, and central indicia white LEDs 4 arranged to selectively display the words STOP, as shown in Figure 1 , when the main array will be emitting red light, and GO, as shown in Figure 2, when the main array will be emitting green light. The background to the screen between the LEDs is suitably formed of a non-reflective material. (In Fig- ures 1 and 2, the words STOP and GO are illustrated by solid lines, but it will be understood that the letters will be displayed by the selective illumination of a plurality of LEDs located to give the effect of individual letters when viewed from the normal viewing distance).

[0016] One display unit will suitably be placed at one end of the roadworks and another will be placed at the opposite end and facing the opposite direction. Where it is necessary to control traffic emerging from another direction such as a side road, additional display units can be employed. Further, to increase the visibility of the signals, pairs of the display units may be located together, for example on either side of the road.

[0017] Figure 3 is a block circuit diagram of the display controller, which is suitably a hand-held device which the operator might conveniently have mounted on a belt around his or her waist. The display controller is conveniently configured with a number of selector keys arranged to form a keyboard, typically eight, each representing a distinct phase of communication, and a restart key. Each of the selector buttons is provided with a respective pair of LED indicators, one red and one green, used to indicate the status of the display units on the particular phase.

[0018] The system uses two clocks, a central clock 30 and a mimic clock 31 . The central clock 31 sends a multi-astable signal to a decimal counter 32 and a memory device 33. The decimal counter 32, together with an inverter 34, generates a signal which is present at the keyboard 35, one key at a time, and will repeat. (This means that only one "phase" can be selected at a time).

[0019] Once a key is pressed it makes a circuit allowing the memory 33 to store the selected keystroke, which will then stop the central clock 31 and force a system halt. The memory 33 will not accept any new inputs until the restart key 36 is pressed. Once a key has been pressed following a restart, the TX mimic LED indicators 37 will then display the selection alongside the relevant phase key in the keyboard 35.

[0020] The memory system 33 is linked to a Decimal to BCD encoder 38 will convert the number of the selected phase or channel to BCD (binary code decimal). The output of the BCD encoder 38 is linked to a TX (transmitter) 39 which transmits a constant common BCD signal. This BCD function prevents two phases being selected and becoming live. It is sending 1 to 8 decimal in BCD format, as set out in the Table below: Table: Channel system

[0021] The system transmits a 4-bit binary (BCD) signal and so is capable of supporting up to 15 Channels, although the system as described is configured for only eight channels or phases.

[0022] To cancel the signal or phase the restart key 36 is pressed, which is linked to the Mimic clock 31 , which then restarts the system forcing a general reset, and keyboard scanning continues. A radio receiver 40 receives a return BCD signal from the selected remote display unit and this is converted to decimal to provide an output switching on the respective one of the RX mimic LEDs 41 to confirm which unit is selected.

[0023] Referring now to Figure 4, the radio receiver (RX) 50 in the display unit is connected a BCD decoder 51 , which converts the binary signal to decimal. The signal is then linked to a rotary selector switch 52 which has at least 8Throw1 POLE configuration. This switch 52 will allow the operator to preselect the BCD transmission mode allowing the display controller to identify which phase it will run on. Once a valid signal is received by the radio receiver 50 a delay timer 53 initiates to delay the unit turning to the green GO indication. If the signal is lost or cancelled the Base unit will immediately return to red. Red/Green switching is done using a DPDT relay 54, driven by the delay timer 53. The delay timer lasts for 1 .5 seconds and will allow the operator to cancel a signal before changing to green. The display unit will incorporate batteries suitable for providing extended operation. If the battery charge becomes low, the base unit will transmit a half signal (astable or tick) rather than the constant signal to signal battery low. The resultant flashing light on the system controller alerts the operator to the need to replace the display unit for one with charged batteries. On full battery failure of a lighting unit, no radio signal will be fed back, and the system controller registers an error and arrests the system. [0024] The display units at opposite ends of the roadworks will be set to different phases, to allow them to be operated independently, while never both showing green/GO. However, a pair of display units may be set to the same phase by the rotor switches 52 to result in a mirrored phase. This pairing allows more base units to run and greater visibility for the motorist at each end of the roadworks. It will be appreciated that it would be possible to operate more than two display units on the same phase, provided, of course, that the display units in a phase all face the same direction.

[0025] A second panel 55 on the rotor will then divert the return signal back to a TX radio 56, which then communicates the successful "change" back to the system controller.

[0026] LEDs work on different voltages, and the display controller is configured to allow channels to be set at different voltages to control brightness. For example 2-state LEDs require a lower voltage to drive the red state than that required to drive the green state. The display controllers are also configured to increase the voltage to the LEDs in bright conditions to increase their light output and therefore their visibility. Sensors may be provided in the array to detect ambient light to control this function.

[0027] A constant radio command received will turn the appropriate display unit(s) to green. The display unit will transmit back, confirming green status. This will be the key for preventing conflicts. The display unit has a "Lamps off" function allowing the device to run in test with no visibility to the traffic. [0028] At present the maximum range that stop and go units are allowed be used is two hundred metres. That is the entire site, so the maximum from controller to display unit is 100m. However, the system of the invention is proposed to extend to one hundred and fifty metres. The radio system is packet switched to minimise radio interference.

[0029] The units could be upgraded with a separate camera system installed on each head, to transmit back to an onsite recorder, thus allowing the operative to work from a vehicle, and react to traffic tides. The recordings could then be used as traffic counts for council or general quality information. [0030] The system controller could be wrist/ forearm mounted, thereby freeing up both hands, and saving unnecessary 'gripping' of the unit. The system controller may be provided with a separate belt battery, which could be charged from the vehicle. A suitable connector would be required between the system controller and the antenna and battery, the battery. If required, the system controller unit could plug into a display unit for emergency power.

[0031] The controller will display which display unit is displaying green at present; it will not allow two phases to be green at any one time. If this were to occur, a conflict will be registered and an arrest will occur and will need to be unlocked by the user. The unit will also display what phase has failed. If the unit is to be used in a vehicle, an external antenna may be used.

[0032] A booster station could be used for sites with objects in the way, as radio systems require clear line of site.

[0033] The system controller will have built in battery monitoring and alerts for low battery. The controller will also display what base units have low battery. If a display unit fails to display a red stop signal when in its default mode, a signal is transmitted to the controller, causing the red mimic LED next to the respective selector key to flash red and also causing the system to lock out, requiring the operator to remedy the fault (or replace the display unit) and the press the reset key to permit normal operation to be resumed. [0034] While an embodiment of the invention has been illustrated using electronics comprising discrete components, the person skilled in the art will appreciate that the system could be realised in other ways, for example using a programmable micro controller or even a custom chip.