GB2618800A

GB2618800A - Temporary traffic control system

Info

Publication number: GB2618800A
Application number: GB2207183.1A
Authority: GB
Inventors: Hudson Darren; Okey Ian; Michael Hutchinson Peter
Original assignee: AGD Systems Ltd
Current assignee: AGD Systems Ltd
Priority date: 2022-05-17
Filing date: 2022-05-17
Publication date: 2023-11-22
Also published as: GB202207183D0

Abstract

A wireless portable traffic signal unit 100 (e.g. for use in a temporary traffic light system comprising other such units), comprises a system controller 124 with multiple modes of operation. In a first mode, it generates control signals for causing the traffic signal units to present signals in a phase-based sequence defined by preconfigured timing logic. In a second mode, it instead receives control signals from a separate control unit (140,Fig.3) for causing the traffic signal units to present signals in a stage-based sequence defined by a preconfigured control scheme. The mode may be indicated on a display (120,Fig.3). Also disclosed is a portable control unit (140, Fig.3) comprising an input for receiving a preconfigured control scheme (e.g. implementing an intergreen matrix) and a transmitter for transmitting control signals to cause portable traffic signal units to present signals in a stage-based sequence. The portable control unit may store multiple such preconfigured control schemes, selectable by a user, which cannot be manually altered.

Description

TEMPORARY TRAFFIC CONTROL SYSTEM Field of the Invention This invention relates generally to a temporary traffic control system of the type comprising two or more temporary (and portable) traffic control signals; and to a portable traffic signal apparatus and a portable control unit for use in a temporary traffic control system

Background of the Invention

Temporary (and portable) traffic control signal devices are well known and in widespread use, either as a substitute for malfunctioning (or otherwise out-of-permanent traffic control signals, or to provide traffic control on a portion of roadway where roadworks or service maintenance works (or the like) cause an obstruction or restriction to normal traffic/pedestrian movement thereon.

In a temporary traffic control system comprising at least two traffic signals (e.g. at least one for each direction of controlled traffic flow), one of the traffic signals will be configured as a 'Master' and the or each other traffic signal will be configured as Signal only'. There is only ever one 'Master' traffic signal in a system, and the Master can communicate with all of the other 'Signal only' traffic signals in the system. The 'Signal only' traffic signals cannot communicate with each other, they can only communicate with the 'Master' traffic signal.

Of necessity, and because the traffic signal controls must be set up at the roadside by a traffic management operator (TMO), temporary (and portable) traffic and pedestrian signal installations are usually deployed using simple traffic phasing techniques. The control cycles are, essentially, pre-programmed into the Master control unit, and the parameters are set by the TMO to fit the specific circumstances and configuration of the system. The Master traffic signal then communicates traffic control signals to the 'Signal only' traffic signals in order to implement the signal phasing of the system.

Typically, to implement control of a system, the TMO configures the Master traffic signal (via the control panel) to: * Indicate the number of traffic signals in the system; * Indicate whether any of the signals are pedestrian phases; * Set the 'All-Red' time for the system -this is the minimum time required for vehicles (or pedestrians) to clear the last green phase before the next green phase is called; * Set the maximum green time that each phase is able to run -this is usually dependent on how busy each roadway being controlled is, whereby the busier the road, the greater will be the maximum green time, in general.

The simple nature of the built-in phasing logic means that it is low-risk to configure the all-red safety timings at the roadside, as very little measurement or calculation is required. In a common method for calculating the all-red time of a system, for every 10m of signal head separation, 1 second of all-red time is set. For example, a pair of traffic signals separated by 50m in a set of roadworks would have 5 seconds all-red time set in the Master control unit. Assuming that these parameters are correctly set, the safety of the system is assured by the pre-programmed control logic. Two green phases can never come on together, unless they are ';linked' by the TMO when setting the controls. Linked lights are usually used when to traffic signals are facing the same stream of traffic, and always have the same green time as the two phases are locked together in their operation.

Traffic signals may be (or have the capability to be) configured for either Master or Signal only operation. In Signal only operation, as explained above, the traffic signal responds to instructions from the Master and obeys its own set of simple safety rules. Only the Master has a (limited) set of programmable timing functions available.

Each flow of traffic required to be controlled will have its own traffic signal (or perhaps two linked traffic signals, depending on the size of the road), whose operation is known as a phase and, at any one time, only one phase will ever be green, with all other phases on red. Between each green phase, there will be an all-red period, when all phases are red, before the next phase turns green. In some implementations, particularly those controlling more than just two-way traffic along a single roadway, this can cause significant efficiency issues, leading to delays, driver frustration and, ultimately, possible safety problems.

In permanent traffic control systems, these issues can be addressed by the use of stages, which are specially configured groups of phases that run together to create a particular set of permitted vehicle movements. The use of stages can significantly increase the efficiency of a junction and reduce delays. However, stages can be complicated to configured correctly, and it is extremely easy to get a stage configuration wrong, which could lead to catastrophic signalling conditions. For that reason, the configuration of temporary traffic signals at the roadside is kept as simple as possible, and uses the failsafe all-red' timing control model described above.

When designing a (permanent) traffic signal junction, rather than the simple all-red' timing described above, parameters known as phase intergreens are used as design inputs. A phase intergreen is defined as the clearance time between the green period terminating on a traffic signal phase which is losing right of way and the start of the green period on a phase gaining right of way where vehicle movements conflict. The intergreen period ensures that clearance time exists for traffic losing right of way to sufficiently clear the junction before traffic gaining right of way on conflicting movements arrives. Specialist engineers, when designing phasing control for permanent traffic signal systems, first calculate an intergreen matrix that describes the minimum intergreens between phases by using a model of the junction, identifying critical conflict points between phases and then calculating the minimum intergreens accordingly. The intergreen matrix is then transferred to a software package for making traffic signal calculations and, eventually, designing the control logic for controlling the traffic signal system. An example of an intergreen matrix is shown below, for illustrative purposes: Inter 'e en atnx

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XEMEMEIEISMIll 12 2 Once designed, the control program requires rigorous testing and simulation to ensure that it is safe, before it can be implemented at the junction itself. This is a highly specialist and time consuming process and, for those reasons, is limited to use with permanent traffic signal control systems.

Nevertheless, intergreen timings have a huge advantage over all-red only clearance times, as they can be laid out in a so-called "intergreen matrix" which can optimise these safety timings as one set of signals progress from one permitted set of vehicle movements to another set and, as a result, the efficiency of movement of traffic volumes can be optimised. However, current temporary traffic signals simply do not include the ability to implement complex intergreen-based timings and cycles, as it would be too dangerous for a TMO to attempt to configure them at the roadside. Instead, portable traffic signals operate on the basis of simple phase-based timings and cycles and implement simple clearance timings, which make them easy and safe to configure at the roadside, but makes them relatively poor, when compared with permanent traffic signal systems, in terms of moving traffic volumes efficiently.

It is an object of aspects of the present invention to address at least one or more of these issues.

Statements of Invention

In accordance with a first aspect of the present invention, there is provided a first wireless portable traffic signal unit for use in a temporary traffic signal system comprising one or more other wireless portable traffic signal units, said first portable wireless traffic signal unit comprising a system controller that is selectively configurable between first and second modes of operation, wherein, in said first mode of operation, said system controller of said first wireless portable traffic signal unit generates system control signals for causing said first and other wireless portable traffic signal units to present signals in a phase-based sequence defined by preconfigured timing logic in said system controller, and in said second mode of operation, said system controller does not generate system control signals and instead receives system control signals from a separate control unit for causing said first and other wireless portable traffic signal units to present signals in a stage-based sequence defined by a preconfigured control scheme stored in said separate control unit.

In an embodiment, the system controller of the first wireless portable traffic signal unit is selectively configurable between said first and second and a third mode of operation, wherein in said third mode of operation, said system controller does not generate system control signals and instead receives system control signals from the system controller of one of the other wireless portable traffic signal units in said temporary traffic signal system to cause it to present signals in a phase-based sequence.

Beneficially, the first wireless portable traffic signal unit may further comprise a display for indicating the current mode of operation of the system controller. For example, on said display, said first and other traffic signals may be depicted as numbers in said first mode of operation (which is the convention for portable and temporary traffic signal control schemes), and as letters in said second mode of operation (which is the convention for permanent traffic signal systems).

In accordance with a second aspect of the invention, there is provided a portable control unit for a temporary traffic signal system comprising a plurality of wireless portable traffic signal units, said portable control unit comprising an input for receiving a preconfigured traffic signal system control scheme in the form of executable instructions, a memory for storing said executable instructions, and a system control processor configured to execute said instructions stored in said memory to generate control signals, the portable control unit further comprising a transmitter for selectively wirelessly transmitting said control signals to said portable traffic signal units to cause them to present signals in a stage-based sequence defined by said predefined control scheme.

Beneficially, the processor is preconfigured with an error-checking module configured to check the predefined control scheme for errors.

Beneficially, said predefined control scheme may implement an intergreen matrix, and/or include one or more stages, as it can in permanent traffic signal systems (but not in known temporary traffic signal systems).

In an embodiment, the input may comprise a wireless receiver for receiving data representative of said preconfigured traffic signal system control scheme from a remote location. The input may, alternatively or in addition, comprise a user interface for enabling local loading of said executable instructions to said memory.

The executable instructions may beneficially be protected within said memory such that they cannot be altered, overwritten or deleted from said control unit.

Optionally, the memory may be configured to store two or more sets of instructions corresponding to two or more respective preconfigured traffic signal system control 20 schemes, and the portable control unit may further comprise means for enabling a user to select one of said control schemes for execution.

In an embodiment, the portable control unit may further comprise a display for displaying data representative of said two or more traffic signal system control schemes, and selection means for enabling a user to select one of said control 25 schemes.

Optionally, the portable control unit may further comprise a monitoring module for receiving status data in respect of said plurality of portable traffic signal units. In this case, a wireless transmitting device may be provided for transmitting said status data to a remote location.

In accordance with another aspect of the present invention, there is provided a computer-implementable program product which, when loaded and run on a system controller of a wireless portable traffic signal capable of only a first, phase-based mode of operation, causes said system controller to be additionally capable of a second, stage-based mode of operation in which it can receive control signals from a control unit substantially as described above, such that a user can selectively configured the traffic signal for said first or said second mode of operation.

Accordingly, it is envisaged that the software of exiting portable wireless traffic signal units can be upgraded to offer the second mode of operation, in which they can respond to control signals from the above-described control unit. The user/TMO can select the mode of operation as required. Thus, the traffic signal unit could still be utilized in the conventional (first) phase-based mode of operation (either as the 'Master' or 'Signal only' traffic signal unit); but it could also be configured for stage-based operation, by selecting the second mode of operation, and providing, within the traffic signal system, a portable control unit substantially as described above.

In accordance with yet another aspect of the invention, there is provided a temporary traffic signal system comprising two or more portable traffic signal units and a portable control unit, each said portable traffic signal unit comprising a receiver for receiving control signals configured to cause it to present signals, the portable control unit comprising a system control processor, an input for receiving a preconfigured traffic signal system control scheme in the form of executable instructions, and a memory for storing said executable instructions, said system control processor being configured to execute said instructions to generate control signals, the portable control unit further comprising a transmitter for selectively transmitting said control signals to said portable traffic signal units to cause them to present signals in a sequence defined by said predefined control scheme.

In accordance with yet another aspect of the invention, there is provided a temporary traffic signal system comprising a portable master traffic signal unit substantially as described above, one or more other traffic signal units, and a portable control unit substantially as described above.

These and other aspects of the invention will be apparent from the following detailed description.

Brief Description of the Drawings

An embodiment of the present invention will now be described, by way of example only, and with reference to the accompanying drawings, in which: Figure 1 illustrates schematically a simple temporary traffic signal system, comprising two traffic signal units, with one of the traffic signal units being designated as the 'Master'; Figure 2 is a schematic diagram of the traffic signal system of Figure 2; Figure 3 illustrates schematically a simple temporary traffic signal system according to an exemplary embodiment of the invention, with all traffic signal units operating in a "controlled" mode; Figure 4 is a schematic diagram of the traffic signal system of Figure 3, and Figure 5 is a schematic side-by-side exemplary illustration of the improved junction efficiency between control using a) a known Master controller in a temporary traffic signal unit of a temporary traffic signal system, and b) a portable control unit is according to an exemplary embodiment of an aspect the invention used in the same temporary traffic signal system.

Detailed Description

Referring to Figures 1 and 2 of the drawings, a simple temporary traffic signal system comprises a pair of portable traffic signal units 100. Each traffic signal unit 100 comprises a base 102, a pole 104 extending vertically from the base 102, and a signal head 106 supported by the pole 104. The base 102 is mounted upon two wheels 108, enabling the signal unit 100 to be portable and easily moved between locations. However, it should be noted that the signal unit may not necessarily include wheels, depending on individual requirements of the overall traffic signal system.

The signal head 106, in this exemplary embodiment, includes three variable-intensity lights 110, hereinafter referred to simply as "lights". In other embodiments, a greater or lesser number of lights 110 may be provided, and may comprise pedestrian indicators or filter arrows, for example, but in the embodiment depicted in Figures 1 and 2, three round lights are provided and aligned vertically in the manner of a conventional traffic light. The lights are coloured in common with well-known traffic signal systems such that the upper light is red, the lower light is green, and the middle light is amber.

On top of the signal head 106 is mounted a sensing system 112. The sensing system 112 of the depicted embodiment includes a radar device -in this case, a frequency-modulated continuous wave (FMCVV) radar device -which operates to provide range and/or speed readings related to vehicles approaching the signal unit 100. An ambient light sensor may also be provided in the sensing system 112, which senses ambient light in the vicinity of the signal unit 100. The ambient light sensor may be used to reduce the intensity of the lights in the signal head 106 during low-light operation.

In each of the traffic signal units in the system, the sensing system 112 and signal head 106 are controlled by a signal head controller 116, which in the present embodiment is housed within the base 102. A battery 118 is also provided in the base 102 in order to provide power to the signal unit 100.

At least one of the traffic signal units 100 includes a base station 120, housed in the base 102, wherein a traffic signal unit comprising a base station can be designated as a 'Master' or as a 'Signal only' unit, as required. In a conventional temporary traffic signal system, only one of the traffic signal units in a system would be designated as the 'Master', and all of the other traffic signal units in the system would be 'Signal only' units. In Figures 1 and 2, the signal head controller and the sensing system have been omitted from the Master base station, for the sake of clarity.

As well as the signal head controller and the sensing system, the base station 120 houses a system controller 124, which is configured to execute simple control instructions stored in a memory 122, and provide control signals to any of the other traffic signal units 100 in the traffic signal system, as well as to its own signal head controller 116. As such, central control of a lighting pattern to be displayed by any of the signal heads 106 is enabled. Communication between the base station 116 and any traffic signal unit 100 is provided by way of a transceiver 126 located in the base station 116 and a corresponding transceiver 128 located in the traffic signal unit 100.

The use of transceivers 126, 128 enables two-way communication between the base station 116 and any of the traffic signal units 100, but 'Signal only' units can only communicate with the base station 120 (or 'Masten, they cannot communicate with each other.

In use, the system controller 124 will provide control signals to the signal head controller 116 of each traffic signal unit 100 in the traffic signal system (including that of the Master traffic signal unit). These signals will cause the signal head 106 of the traffic signal unit 100 to present signals in a phase-based sequence defined by the system controller 124.

In a known traffic signal system of this type, in order to implement control of a system, the TMO configures the system controller 124 (via the control panel) to: * Indicate the number of traffic signals in the system; * Indicate whether any of the signals are pedestrian phases; * Set the 'All-Red' time for the system -this is the minimum time required for vehicles (or pedestrians) to clear the last green phase before the next green phase is called; * Set the maximum green time that each phase is able to run -this is usually dependent on how busy each roadway being controlled is, whereby the busier the road, the greater will be the maximum green time, in general.

The system controller 124 then uses these inputs and its built-in phasing logic to generate control instructions (based on the all-red timings described above) that are 20 stored in a memory 130 and called by the system controller 124 to implement a simple control cycle to control the traffic signal units 100 in the system.

The base station 120 further comprises a switch 132, by means of which a TMO can change the configuration of the respective 'Master' traffic signal unit to a 'Signal only' or "controlled" mode. In this "controlled" mode, the system controller 124 is effectively disabled, and operation of the traffic signal system is, instead, controlled by a separate control unit 140. In some embodiments, the 'Signal only' traffic signal units may also include the switch 132, by means of which the TMO can change the configuration of the respective 'Signal only' traffic signal unit to a "controlled" mode. In the "controlled" mode, all of the traffic signal units 100 will only respond to control signals from the control unit (140, Figures 3 and 4), and the control unit 140 can be configured to control all traffic signal units in the traffic signal system set to the "controlled" mode.

Referring now to Figures 3 and 4 of the drawings, in a known wireless portable traffic signal unit, its mode of operation is displayed on a screen. In a conventional traffic signal unit, the system controller can be configured as a 'Master or 'Signal only' (Signal 1) unit. Only one Master would be designated as such, and the rest of the traffic signal units in a system would be designated as 'Signal only and receive system control signals from the Master for phase-based operation. It is envisaged that the software of known traffic signal units could be updated or modified to include a third mode of operation (Signal 2) and, when all of the traffic signal units in a temporary traffic signal system are in this 'Signal only' mode, they receive system control signals from the control unit 140.

The control unit 140 comprises a base 142 that houses a system controller 144, which is configured to provide control signals to all of the other traffic signal units 100 in the traffic signal system. As such, central control of a lighting pattern to be displayed by any of the signal heads 106 is enabled. Communication between the control unit 140 and any traffic signal unit 100 is provided by way of a transceiver 146 located in the base 142 and a corresponding transceiver 148 located in the base 142. The use of transceivers 146, 148 enables two-way communication between the control unit 140 and any of the traffic signal units 100, but the traffic signal units 100 can only communicate with the control unit 140, they cannot communicate with each other. In this mode, the traffic signal unit that includes the base station 120, and has the capability to be designated as the 'Master is, effectively, operating in a 'Signal only' mode, just like the, or all of the, other traffic signal units in the system. It will be noted that all of the traffic signal units 100 are depicted as 'Signal only' units in Figure 4 of the drawings, but it will be appreciated that at least one of the units 100 may have the ability to be designated as a Master when only simple all-red timings are required for the system.

The control unit 140 is portable, and may be mounted upon two wheels 150, enabling the control unit 140 to be portable and easily moved between locations.

However, it should be noted that the control unit may not necessarily include wheels, depending on individual requirements of the overall traffic signal system. A sensing system 152 may be mounted on a pole 154 extending vertically from the base 142 of the control unit 140. The control unit 140 further includes a battery 156 to provide power to the control unit, and a memory 158, both housed within the base 142.

In use, the control unit can receive, via its transceiver 146, a set of control instructions that have been designed and tested remotely. Alternatively, the control instructions can be pre-loaded into the memory 158 before the control unit 140 is transported to the site where the traffic signal system is required. This set of control instructions allows for a much more complex, stage-based control cycle, based on the intergreen timings described above, and can be rigorously simulated and tested lo before transmission to the control unit 140. The control instructions are stored in the memory 158 and called by the system controller 144 of the control unit 140, which generates control signals and transmits them to the signal heads 106 of the traffic signal units 100, via the transceiver 148, to implement the control cycle. Multiple different such sets of control instructions can be received and stored in the memory 158, in which case, a TMO can select one from the available sets of control instructions at the roadside (via a control panel (not shown)).

The control unit is configured to monitor the status of all the signals under its control and the communications devices in the control unit enable the status of the signalling schemes to be monitored remotely, thus further improving the safety of the system.

In contrast to a 'Master' base station 120, the control unit 140 can run stages and intergreen matrices of the type described above, similar to the controls used in permanent traffic signal systems. For reasons of safety, and like a permanent traffic signal controller, the control unit 140 must be configured by means of control program(s) developed using specialist software design tools that can run all the safety timings and simulations to ensure that the control cycles are fit for use before being deployed within the traffic signal system. It is not permitted to allow these types of configuration by a TMO on a Master base station or controller at the roadside. Software packages, such as 'Signal Studio', are known and widely used by engineers to calculate signal timings and simulate and test control solutions for permanent traffic signal systems, and such signal controls can be designed and simulated for a set of temporary traffic signals using these software packages, which will be familiar to those skilled in the art. As such, the method for designing a set of signal timings for a temporary traffic signal system, for use by a control unit of an aspect of the invention, need not be described in any further detail herein.

The ability to run more complex control cycles using intergreen matrices in a temporary traffic signal system (as in permanent traffic signal systems) has numerous benefits in terms of the efficiency of the portion of road or junction at which is deployed. This is illustrated schematically in Figures 5a and 5b of the drawings.

Figure 5a shows the phased based function of conventional portable signals.

This is the basic phasing that can be set up from one of the controllers set as a Master with all the others set in basic signal only mode.

Figure 5b shows the stage based function that can be delivered with a designed safety plan and the implementation of an intergreen matrix using a portable control unit of the type described above. In the system represented by Figure 5b, all the signal controllers of all of the portable traffic signal units have been set to the second advanced signal mode (Signal 2 -Figure 3) with no Master set. There are three more signal units added, as more movements are now possible (phases D & E). The control unit (140-Figure 3) now directly controls all the signals.

The signal notation in the diagrams is taken originally from BS505 but used in all traffic control schematics taken from Appendix A.2 from Traffic Signs Manual 20 Chapter 6.

Referring to Figure 5a of the drawings, in a temporary traffic signal system at a T-junction, a set of two linked traffic signal units (1, 2), a third traffic signal (3) and a pedestrian signal are employed. If the Master base station of a known temporary traffic signal unit is used to configure the signal timings for these traffic signal units, using the roadside configuration described above via the control panel, the signal timings can be represented as shown in the table of Figure 5a. It will be apparent to a person skilled in the art that the system operation is cyclic, allowing movement in both directions along the main carriageway, and then from the side road and then pedestrians, in turn, with linked phases and fixed periods of all-red time between each permitted movement.

Referring now to Figure 5b, there is illustrated a signal timing diagram from a simulation of the same junction control, using the same, and three additional, temporary traffic signal units, but now utilising the portable control unit of an aspect of the invention, which allows for control using designed stages and implementation of the above-mentioned intergreen matrix. It will be apparent that the efficiency of the junction is significantly improved, with the virtual elimination of all-red periods, when no movements are permitted. In addition, the unlinking of the previously linked signals or phases (A, B) permits much more efficient timings in respect of those phases. It will be apparent that, in view of the complex nature of the timings in the table of Figure 5b, this type of implementation cannot be permitted for configuration at the roadside using a known Master base station as the calculation of intergreen timings is complex and dependent on many different variables that would be beyond the capability of the built-in timing logic of a controller of a conventional portable traffic signal unit.

Conventionally, portable (temporary) signals use numbers to indicate phases, whereas permanent signals use letters for phases. In an exemplary embodiment of the invention, operation of a traffic signal unit when its base station is configured as the Master may be identified by numbers that are applied to the phases, whereas when base station is configured so that the signal unit is controlled by the control unit 140, this may be indicated on a display (not shown) on the base station by applying letters to the phases. This acts as an indicator that the "controlled" mode is selected as it more readily identifies the cross-over of operation The software used to design the control schemes for the control unit knows the limits and functions of the signals in the "controlled" mode, and will not permit designs that cannot be implemented by the hardware. As referenced above, the pre-designed control schemes can be sent to the control unit wirelessly, so schemes can be updated to improve efficiency or if the works change. However, it is envisaged that the control schemes could, alternatively or additionally, be pre-loaded into the memory of the control unit prior to its transport on-site. The control unit may be configured to hold more than one scheme, in which case, multiple such schemes may be displayed in a window, each with a unique design reference.

New or alternate schemes may only be selectable by an operative on site to implement them and, in some embodiments at least, cannot be implemented remotely. An operator can change between schemes, but not change a scheme. This may be, for example, to facilitate a pre-agreed change to the road layout as works progress which requires the signalling scheme to be updated.

The design software for a control scheme for use in the control unit is equipped with safety notes, automatic checks on the orientation of signals (i.e. two signals with conflicting greens are not pointing in similar directions), as well as normal help files in context, none of which can be provided on a base station of a known traffic signal unit operating in the 'Master' mode. The design software for control schemes for use in the control unit can run a complete simulation, as for permanent traffic signal systems.

It will be apparent to a person skilled in the art, from the foregoing description, that modifications and variations can be made to the described embodiments without departing from the scope of the invention as defined by the appended claims.

Claims

CLAIMS1. A first wireless portable traffic signal unit for use in a temporary traffic signal system comprising one or more other wireless portable traffic signal units, said first portable wireless traffic signal unit comprising a system controller that is selectively configurable between first and second modes of operation, wherein, in said first mode of operation, said system controller of said first wireless portable traffic signal unit generates system control signals for causing said first and other wireless portable traffic signal units to present signals in a phase-based sequence defined by preconfigured timing logic in said system controller, and in said second mode of operation, said system controller does not generate system control signals and instead receives system control signals from a separate control unit for causing said first and other wireless portable traffic signal units to present signals in a stage-based sequence defined by a preconfigured control scheme stored in said separate control unit.
2. A first wireless portable traffic signal unit according to claim 1, wherein the system controller thereof is selectively configurable between said first and second and a third mode of operation, wherein in said third mode of operation, said system controller does not generate system control signals and instead receives system control signals from the system controller of one of the other wireless portable traffic signal units in said temporary traffic signal system to cause it to present signals in a phase-based sequence.
3. A first wireless portable traffic signal unit according to claim 1 or claim 2, further comprising a display for indicating the current mode of operation of the system controller.
4. A first wireless portable traffic signal unit according to claim 3, wherein, on said display, said master and other traffic signals are depicted as numbers in said first mode of operation, and as letters in said second mode of operation.
5. A portable control unit for a temporary traffic signal system comprising a plurality of portable traffic signal units, said portable control unit comprising an input for receiving a preconfigured traffic signal system control scheme in the form of executable instructions, a memory for storing said executable instructions, and a system control processor configured to execute said instructions stored in said memory to generate control signals, the portable control unit further comprising a transmitter for selectively transmitting said control signals to said portable traffic signal units to cause them to present signals in a stage-based sequence defined by said predefined control scheme.
6. A portable control unit according to claim 5, wherein said predefined control scheme implements an intergreen matrix.
7. A portable control unit according to claim 5 or claim 6, wherein said input comprises a wireless receiver for receiving data representative of said preconfigured traffic signal system control scheme from a remote location.
8. A portable control unit according to any of claims 5 to 7, wherein said input comprises a user interface for enabling local loading of said executable instructions 15 to said memory.
9. A portable control unit according to any of claims 5 to 8, wherein said executable instructions are protected within said memory such that they cannot be manually altered, overwritten or deleted by an operative at said control unit.
10. A portable control unit according to any of claims 5 to 9, wherein said memory is configured to store two or more sets of instructions corresponding to two or more respective preconfigured traffic signal system control schemes, and the portable control unit further comprises means for enabling a user to select one of said control schemes for execution.
11. A portable control unit according to claim 10, further comprising a display for displaying data representative of said two or more traffic signal system control schemes, and selection means for enabling a user to select one of said control schemes.
12. A portable control unit according to any of claims 5 to 11, further comprising a monitoring module for receiving status data in respect of said plurality of portable traffic signal units.
13. A portable control unit according to claim 12, further comprising a wireless transmitting device for transmitting said status data to a remote location.
14. A temporary traffic signal system comprising two or more portable traffic signal units and a portable control unit, each said portable traffic signal unit comprising a receiver for receiving control signals configured to cause it to present signals, the portable control unit comprising a system control processor, an input for receiving a preconfigured traffic signal system control scheme in the form of executable instructions, and a memory for storing said executable instructions, said system control processor being configured to execute said instructions to generate control signals, the portable control unit further comprising a transmitter for selectively transmitting said control signals to said portable traffic signal units to cause them to present signals in a sequence defined by said predefined control scheme.
15. A temporary traffic signal system comprising a plurality of first wireless portable traffic signal units according to any of claims 1 to 4" and a portable control unit according to any of claims 5 to 14.
16. A computer-implementable program product which, when loaded and run on a system controller of a wireless portable traffic signal unit capable only of a first, phase-based mode of operation, causes said system controller to be additionally capable of a second, stage-based mode of operation in which it can receive and implement control signals from a portable control unit according to any of claims 5 to 13, such that, in use, a user can selectively configure the traffic signal for said first or said second mode of operation.