GB2386730A

GB2386730A - Roadside safety system

Info

Publication number: GB2386730A
Application number: GB0206730A
Authority: GB
Inventors: Ronald Barnes
Original assignee: Systems Engineering and Assessment Ltd
Current assignee: Systems Engineering and Assessment Ltd
Priority date: 2002-03-22
Filing date: 2002-03-22
Publication date: 2003-09-24
Also published as: WO2003080937B1; GB0206730D0; WO2003080937A1; AU2003222954A1

Abstract

A safety system for alerting roadside personnel to detected incursions by approaching vehicles into designated safe area or areas; the said system comprising: a plurality of traffic cones 14 or like traffic warning elements for defining a visible boundary along a roadside or carriageway boundary. Each cone or warning element has impact detecting means 10 for detecting an impact with an approaching vehicle, and signal generating means (40, 42, 44) for generating an alarm activating signal in response to a detected impact, and, alarm means (53, 60, 63) activated in response to the generation of an alarm activating signal.

Description

BOUNDARY PROTECTION SYSTEM and ROAI)SIDE SAFETY SYSTEM

This invention relates to a boundary protection system and in particular concerns a 5 roadside safety system for detecting and alerting roadside users of potential roadside collisions. Each year in the United Kingdom around 250 people are killed or injured on motorway hard shoulders, road side verges or coned off areas. Research has shown 0 that the majority of accidents on the hard shoulder involve stationary vehicles being hit by other vehicles (67%) with 10% of accidents involving pedestrians being hit.

Most accidents are caused by vehicles veering off the main carriageway due to lack of driver concentration. The more serious accidents, as indicated by fatalities, occur on downhill bends and there is a particular problem in the UK with right hand bends 15 where vehicles are more likely to wander onto the hard shoulder. In countries where vehicles drive on the right hand side of the road, down hill left hand bends present similar problems.

Vehicle repair and recovery operatives are particularly exposed to the dangers of the 2 o roadside and in 1998 six recovery operatives were killed. Four of these people were killed on motorway hard shoulders and two on the main carriageway. Road repair and maintenance personnel are also exposed to the dangers of the roadside, particularly when one or more lanes are cordoned off using traffic cones or the like to create a visible boundary between the lanes that are open and closed to traffic.

A recent study by The Hard Shoulder and Roadside Safety Group, a UK industry, government and government agency group, identified a number of practical measures which could be taken to reduce the number of roadside accidents. The study identified 5 the use of technology as one way of improving roadside safety.

One safety system under development and disclosed in GB-A-2,332,320 uses a laser to detect the presence of objects along the laser's line of sight. In this system a laser is mounted on the rear of a recovery vehicle together with a CCTV camera for 10 aligning the laser. A monitor in the cab of the vehicle linked to the CCTV allows an operator to aim the laser along a line of sight corresponding to the motorway hard shoulder/carriageway boundary or roadside verge/carriageway boundary to the rear of the vehicle. The system comprises a laser range finder which allows the operator to set an operational range for the laser, say 150m, so that any object detected by the laser in that range will cause an alarm signal to be activated. The alarm is intended to give the vehicle recovery operative and other parties sufficient time to vacate the roadside area when there is an imminent danger of collision.

There are a number of drawbacks associated with the above mentioned safety system.

2 o One drawback is the complexity of the system. Another drawback is the likely cost of the system due its complexity, and a further drawback is the potential danger of the laser to other road users. The above safety system may also be difficult and time consuming to set up since care must be taken to safely aim the laser before use.

According to one aspect of the invention there is provided a safety system for alerting roadside personnel to detected incursions by approaching vehicles into designated safe area or areas; the said system comprising: 5 a plurality of traffic cones or like traffic warning elements for defining a visible boundary along a roadside or carriageway boundary between at least one carriageway open for traffic and a traffic free area of a road or roadside verge; each cone or warning element having impact detecting means for detecting an impact with an approaching vehicle, and signal generating means for generating an 0 alarm activating signal in response to a detected impact; and, alarm means activated in response to the generation of an alarm activating signal. This system provides a low cost alternative to the above mentioned laser range finder 15 system. The system according to this aspect of the invention is based on the simple principle that the impact of a vehicle with a boundary marker such as a traffic cone or other traffic warning element can be readily detected. This contrasts with the known laser system where a change in the measured distance of the reflected light of the laser range finder due to an object moving into the line of sight causes an alarm 20 to be triggered. The above aspect of the invention avoids the use of relatively expensive laser range finder components and also the use of laser light which could present a hazard to road users if used incorrectly. In this way it is envisaged that a system according to the above aspect of the invention could be produced at sufficiently low cost to enable it to become a standard item of safety equipment for 25 use by highway maintenance personnel and roadside vehicle recovery and repair operatives.

Preferably, the impact detecting means comprises at least one inertia sensor. This readily enables inertial forces due to impact of the cone/warning element to be determined. In preferred embodiments, the impact detecting means comprises at least one, but preferably two, accelerometers. Accelerometers provide accurate signals representative of the inertial loads due to impacts and the like in a reliable and repeatable manner.

Two accelerometers are preferably arranged in orthogonal relation to one another for detecting acceleration of the cone or other boundary marker warning element, due to impact, in two perpendicular directions. In this way it is possible to monitor inertial loads in a two dimensional plane such that inertial loads applied to the cone/warning 15 element in the direction perpendicular to the plane do not affect the accelerometer output signals.

Preferably, the accelerometers detect acceleration in a horizontal plane of the cone or element only. This is advantageous when impact loads, due to say positioning the 2 0 cone/warning element by dropping from say the elevated platform of a truck, are taken into account since the accelerometers will be effectively isolated from these impact loads.

In preferred embodiments, each cone or other warning element further comprises signal processor means for processing output signal(s) from the said impact detecting means. Preferably the signal processing means compares the output signal(s) from the impact determining means with a pre-determined threshold value for determining 5 whether an alarm activating signal is to be generated. In this way a suitable threshold value can be determined so that the sensitivity of the alarm can be adjusted in accordance with an appropriate inertial force, for example l or 2g.

The alarm means may comprise vehicle systems such as the horn and/or lights of a 0 service or safety vehicle, or may alternatively comprise a dedicated audible, visible, or vibrating alarm. Ike alarm means may be remotely positioned with respect to the respective cone or other element. In preferred embodiments the alarm comprises a plurality of personal alerting units connected by wireless communication links to a base station having a transceiver for receiving alarm activating signals from 5 respective cones or other traffic warning elements having respective transmitters, and;< for transmitting an alarm activating signal to the respective personal alerting units.

In a preferred embodiment, the safety system further comprises indicator means for indicating the operational status of the system. In this way the system can determine 20 the operational status of the system components and also whether the system is functioning satisfactory. Each cone or other warning element and/or personal alerting unit may be provided with an indicator for indicating its operational status.

Additionally or alternatively the operational status of the cone or other element may be remotely monitored by the base station via the wireless communication links.

Preferably the wireless communication links are radio frequency communication links. In preferred embodiments the operational radio frequency band is the unlicensed ISM band (United Kingdom), for example using a frequency of 434MHz.

5 According to another aspect of the invention there is provided a traffic cone or other like warning element comprising means for generating an alarm signal in response to impact thereof. In preferred embodiments the means for generating the alarm signal is a single unit capable of being mounted at least partially internally of the cone, preferably in the apex region so that the cones may be stacked in nested configuration 10 so in such a way that each cone adds only 20% of its height to the height of the nested stack. According to another aspect of the invention there is provided an impact alarm apparatus for a traffic cone or other like traffic warning element.

According to another aspect of the invention there is provided a method of detecting movement of approaching vehicles across a visible boundary into a designated safe area; the said method comprising the steps of: positioning a plurality of traffic cones or like traffic warning elements for defining a visible boundary along a roadside or 2 o carriageway boundary between at least one carriageway open for traffic and a traffic free area of a road or roadside verge; each cone or warning element having impact detecting means for detecting an impact with an approaching vehicle, and signal generating means for generating an alarm activating signal in response to a detected impact; and, activating an alarm in response to the generation of an alarm activating signal.

The cones or other warning elements may be positioned along the edge of a motorway hard shoulder, other road side verge or roadwork area along the line of a carriageway boundary, and spaced apart from one another by say 5-20m depending on the curvature of the road or the boundary being defined. In the case of a recovery or 5 service repair vehicle attending a disabled vehicle the cones can be positioned prior to the recovery vehicle arriving at the vehicle to be repaired/recovered.

The aforementioned system can also be used to define temporary boundaries and also to monitor the boundaries to protect areas from unauthorised vehicular access, fores 10 example by positioning a series of cones in close proximity to one another, say 1-2 meters apart and lowering the threshold value of the signal processor so that relatively low speed impacts cause the alarm to be activated. This could be useful in situations where a temporary boundary is required, for example around a parking bay to ensure that unlawful parking is avoided, particularly if the parking bay is required for a 15 service or delivery vehicle.

Various embodiments of the invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a side view of an impact detecting apparatus according to an 2 0 embodiment of the invention mounted on a traffic cone; Figure 2 is a side view of an impact detecting apparatus according to another embodiment of the invention mounted in a traffic cone; Figure 3 is a plan view schematically showing the position of the apparatus of Figure 2 positioned near the apex of the traffic cone;

Figure 4 is a schematic block diagram of an impact detecting apparatus according to an embodiment of the invention; Figure 5 is a schematic block diagram of a base station in a communication system comprising impact detecting apparatus; s Figure 6 is a schematic block diagram of a personal alerting unit for use in a safety system of the present invention; Figure 7 is a schematic representation of the personal alerting unit of Figure 6; and Figure 8 is a plan view schematically showing the position of a plurality of l O traffic cones according to the invention positioned along the boundary between two adjacent lanes of a multi lane highway.

Referring to Figure l, in a first embodiment an impact detecting apparatus 10 is mounted at the apex 12 of a standard traffic cone 14. The impact detecting apparatus 15 comprises a generally cylindrical housing 16 with an enlarged diameter end portion 18 in the form of an end cap. The apex of the traffic cone is provided with an aperture 20 for receiving the cylindrical housing 16 within the interior 22 of the cone. A control unit 24 in the form of a printed circuit board is located within the end portion 18. A pair of batteries 26 are located in the housing for powering the control unit 2 o electronics. The control unit is connected to a quarter wave length antenna 27 which extends coaxially within the cone from an antenna ground plate 28 at the base of the housing 16. A circular disc 30 is located within the cone to enclose the region 22 containing the impact detecting apparatus 10. The disc 30 prevents complete nesting of adjacent cones when stacked so that the apex of the next cone in the stack does not 25 enter the region 22 and damage the detecting apparatus 12.

Referring to Figures 2 and 3 which shows an impact detecting apparatus lO according to a second embodiment. In this arrangement the impact detecting apparatus is fully enclosed within the interior region 22 of the apex of the cone. In this arrangement the quarter wave antenna 27 extends between the aperture 20 at the apex of the cone and 5 the base plate or disc 30 on which the impact detecting apparatus lO is mounted. The antenna ground plane 28 is located on the disc 30 between the disc and the control unit printed circuit board 24. The ground plane 28, control unit 24 and batteries 26 are located in a rectangular box-type housing l 6 through which the antenna extends into the hollow region 22 towards the apex of the cone. The interior region 22 10 between the apex and the disc 30 is filled with an impact resistant material 32 to protect the impact detecting apparatus lO from shock loads during impact of the cone.

Referring to Figure 4, the impact detecting apparatus lO comprises a pair of accelerometers 40 which are arranged perpendicular to one another in the same plane i 15 for detecting impacts in any direction within the plane in which the accelerometers are mounted. The accelerometers are connected to a low power operational amplifier circuit 42 which is capable of detecting output signals from the accelerometers. The output signals from the accelerometers may be positive or negative depending on the direction of the impact. The operational amplifier is capable of detecting both 2 0 positive and negative signals. The operational amplifier 42 is preferably a low power operational amplifier with an integrated comparator semiconductor type device for amplifying the output signals from the accelerometers and determining whether the value of the signals is above a pre-determined threshold value. If the accelerometer output signals are found to be above this threshold value the operational amplifier

sends an output signal to a microprocessor unit 44 which is programmed to activate a radio frequency transceiver 46 for transmitting an alarm activating signal to a base station or a personal alarm unit as described in Figures 5 and 6 respectively. The microprocessor 44 is also connected to one or more LED's mounted on the exterior 5 of the cone for providing visual signals concerning the operational status and other information relating to the detecting apparatus 10. The control unit 24 also comprises a power conditioning unit 48 for powering various components of the unit 24.

In use the impact detecting apparatus 10 transmits an alarm signal by a radio 10 frequency communication link using a coded signal in one of the ISM bands, for example 434 MHZ ISM band, to a base station unit 50 (Figure 5) which sets off a local alarm and/or re-transmits the alarm activating signal to individual personal alarm units 60 (Figure 6).

15 Referring to Figure 5, the base station 50 comprises a first radio frequency transmitter 51 for communication with a plurality of respective transceivers 46. The transceiver 51 is connected to a microprocessor 52 which is programmed to activate an alarm unit 53 connected to the base station microprocessor. The microprocessor 52 may be additionally or alternatively connected to a vehicle alarm system fitted to the same 2 o vehicle as the base station. The base station is powered either by separate batteries or from a vehicle power supply connected to a power conditioning unit 54 which powers the various components of the base station 50 via a power switch and LED display unit 55. The microprocessor 52 is also connected to a second radio frequency transceiver 56 which provides a radio frequency communication link to respective

personal alarm units 60 for retransmission of the alarm activating signal to the personal alarm units.

5 Referring now to Figure 6 and 7 the personal alarm unit 60 is designed to be carried or worn by individual personnel. The personal alarm unit enables the base station to send an alarm signal to individual maintenance personnel, for example to activate an audible alarm in an ear piece worn underneath protective ear defenders. This aspect of the invention is particularly useful for personnel using noisy equipment such as 1 0 hammer drills or grass strimers, for example.

The personal alarm unit shown in Figures 6 and 7 comprises a radio frequency transceiver 60 which communicates with the transceiver 56 in the base station unit.

The transceiver 61 is connected to a central microprocessor 62 which is suitably 15 programmed to control an alerting device 63 which may comprise a visible audible or vibratory alerting device. The microprocessor 62 is also connected to a battery power conditioning unit 63 for powering the components of the alarm unit 60 and also to a switch and LED unit 64. In the embodiment of Figure 7 the alerting device 63 is provided by an audible buzzer 63a and a visible alerting device in the form of a red 20 LED 63b. The buzzer 63a and LED 63b are activated in response to an alarm activating signal being received by the transceiver 61. A green LED 64a is energised to indicate that the alarm unit 60 is switched on and a further LED 64b is energised when the alarm unit is actually Brined, that is to say operational and ready for use.

As shown in Figure 8 a series of cones 14 are aligned to protect an area 70 in the outside or third lane 72 of a three lane highway. In the drawing of Figure 8 the hard shoulder is indicated at 73, the inside lane at 74 and the middle lane 75 with 5 respective boundaries between the lanes being indicated at 76, 77 and 78. The direction of the traffic flow is indicated by the arrow 79 which represents the flow of traffic on roads in countries where vehicles drive on the right hand side of the road as in the United Kingdom. The distance between adjacent cones can vary but may be between say 5 and 20 meters depending on the type of road and radius of the road if 10 the area that is coned off is on a bend in the road. If a vehicle or other object veers into the coned area 70 impact of the vehicle with one or more of the cones will be detected by the respective impact detecting devices 10 fitted to the cones causing the base station 50 to activate the alarm 53 and/or the alarms on the personal alerting units 60 by means of the respective radio communication links. In this way personnel in 15 the vicinity of the area 70 can be warned of the danger and possibility of collision with the vehicle in sufficient time to vacate the area where they are working and move to a safer area.

It will be appreciated that each unit 10 is self contained from an electrical point of 2 0 view within the cone and to avoid false alarms and mitigate against the cones being knocked by roadside or maintenance personnel or deflected by the wind or air currents from passing vehicles the threshold value can be set so that only impact by vehicles or crash debris causes the alarm(s) to be activated. As mentioned above the cones may communicate with a central control system or base station 50 which may be

mounted in a service vehicle, with each cone or base station capable of sending an alarm signal to individual maintenance personnel. The wireless communication links between the cones and the service vehicle base station can also be used to monitor the state of the cones, that is to say the detecting devices lO, and the personal alerting 5 units 60 to provide an alternative form of warning that the detecting devices or alerting units are not working or are not armed in the sense that they have not been switched to an operational mode.

Although the invention has been described with reference to embodiments shown in 10 the accompanying drawings it is to be understood that the invention is not limited to those precise embodiments and that various changes and modifications may be affected without further inventive skill and effort. For example the accelerometers may be replaced by other forms of impact detecting devices such as inertial switches and the like. In addition, further base stations could be used to increase the 15 operational range of the system and provide further alarm units at strategic places within the coned off area. In addition different radio channels (frequencies) may be used for the various radio links in order to minimise interference. The units lO, 50 and 60 may also be provided with low battery warning indicators and operational status indicators such as LED's or audible alerting means to indicate whether the units 2 0 are switched on or off.

Claims

1. A safety system for alerting roadside personnel to detected incursions by approaching vehicles into designated safe area or areas; the said system comprising: 5 at least one traffic cone or like traffic warning element for defining a visible boundary at or along a roadside or carriageway boundary between at least one carriageway open for traffic and a traffic free area of a road or roadside verge; the or each cone or warning element having impact detecting means for detecting an impact with an approaching vehicle, and signal generating means for 10 generating an alarm activating signal in response to a detected impact; and, alarm means activated in response to the generation of an alarm activating signal.

2. A safety system as claimed in Claim 1 wherein the impact detecting means

comprises at least one inertia sensor.

3. A safety system as claimed in Claim 1 or Claim 2 wherein the impact detecting means comprises at least one, but preferably two, accelerometers.

o

4 A safety system as claimed in Claim 3 wherein two accelerometers are arranged in orthogonal relation to one another for detecting acceleration of the cone or other boundary marker warning element, due to impact, in two perpendicular directions.

5. A safety system as claimed in Claim 3 or Claim 4 wherein the accelerometers

detect acceleration in a horizontal plane of the cone or element only.

6. A safety system as claimed in any preceding claim wherein each cone or other warning element further comprises signal processor means for processing output 5 signal(s) from the said impact detecting means.

7. A safety system as claimed in Claim 6 wherein the signal processing means is arranged to compare the output signal(s) from the impact determining means with a pre-determined threshold value for determining whether an alarm activating signal is to be generated.

8. A safety system as claimed in any preceding claim wherein the alarm means comprises the horn and/or lights of a vehicle, or a dedicated audible, visible, or vibrating alarm

9. A safety system as claimed in any preceding claim wherein the alarm means is capable of being remotely positioned with respect to the respective cone or other element. 2 o

10. A safety system as claimed in any preceding claim wherein the alarm comprises a plurality of personal alerting units each having a receiver for connection by wireless communication links to a base station.

11. A safety system as claimed in Claim 10 wherein the said base station comprises

a transceiver for receiving alarm activating signals from respective cones or other traffic waning elements having respective transmitters, and for transmitting an alann activating signal to the respective personal alerting units.

5

12. A safety system as claimed in any preceding claim further comprising indicator means for indicating the operational status of the system.

13. A safety system as claimed in any preceding claim wherein the or each cone or other warning element and/or personal alerting unit comprises an indicator for 10 indicating its operational status.

14. A safety system as claimed in any preceding claim wherein the operational status of the cone or other element is capable of being remotely monitored by a base station via a wireless communication link.

15. A traffic cone or other like warning element comprising means for generating an alarm signal in response to impact of the cone or other warning element.

16. A traffic cone or like warning element as claimed in Claim 15 wherein the o means for generating the alarm signal is a single integral unit capable of being mounted at least partially internally of the cone.

17. A safety system as claimed in Claim 16 wherein the said unit is capable of being mounted in the apex region of the cone so that a plurality of cones may be stacked in

nested configuration in such a way that each cone adds 20% or less of its height to the height of the nested stack.

18. An impact alarm apparatus for a traffic cone or other like traffic warning s element.

19. A method of detecting movement of approaching vehicles across a visible boundary into a designated safe area; the said method comprising the steps of: positioning a plurality of traffic cones or like traffic warning elements to provide a 0 visible boundary along a roadside or carriageway boundary between at least one carriageway open for traffic and a traffic free area of a road or roadside verge; each cone or warning element having impact detecting means for detecting an impact with an approaching vehicle, and signal generating means for generating an alarm activating signal in response to a detected impact, and activating the said impact detecting means 15 of each cone or element for monitoring the said boundary.

20. An impact detection apparatus for use in a safety system for alerting roadside personnel to detected incursions by approaching vehicles into designated safe area or areas; the said system comprising: 2 o impact detecting means for attachment to a traffic cone or other warning element for detecting an impact ofthe cone or element by an approaching vehicle; and, signal generating means for generating an alarm activating signal in response to a detected impact.

21. A safety system substantially as hereinbefore described and with reference to the accompanying drawings.

22. A traffic cone or other warning element substantially as hereinbefore described 5 and with reference to the accompanying drawings.

is Arnendnents to the claims have been filed QS follows CLAIMS

1. A safety system for alerting roadside personnel to detected incursions by approaching vehicles into designated safe area or areas; the said system comprising: 5 at least one traffic cone or like traffic warning element for defining a visible boundary at or along a roadside or carriageway boundary between at least one carriageway open for traffic and a traffic free area of a road or roadside verge; the or each cone or warning element having impact detecting means for detecting an impact with an approaching vehicle, and signal generating means for l o generating an alarm activating signal -in response to a detected impact; and, alarm means activated in response to the generation of an alarm activating signal. 2. A safety system as claimed in Claim 1 wherein the impact detecting means 15 comprises at least one inertia sensor.

20 4. A safety system as claimed in Claim 3 wherein two accelerometers are arranged in orthogonal relation to one another for detecting acceleration ofthe cone or other boundary marker warning element, due to impact, in two perpendicular directions.

-3 5. A safety system as claimed in Claim 3 or Claim 4 wherein the accelerometers detect acceleration in a horizontal plane of the cone or element only.

6. A safety system as claimed in any preceding claim wherein-each cone or other 5 warning element further comprises signal processor means for processing output signal(s) from.the said impact detecting means.

7. A safety system as claimed in Claim 6 wherein the signal processing means is arranged to compare the output signal(s) from the impact determining means with a 1 o pre-determined threshold value for determining whether an alann activating signal is to be generated.

8. A safety system as claimed in any preceding claim wherein the alarm means comprises the horn andlor lights of a vehicle, or a dedicated audible, visible, or 15 vibrating alarm.

9. A safety system as claimed in any preceding claim wherein the alarm means is capable of being remotely positioned with respect to the respective cone or other element. 10. A safety system as claimed in any preceding claim wherein the alarm comprises a plurality of personal alerting units each having a receiver for connection by wireless communication links to a base station.

c)] A safety system as claimed in Claim 10 wherein the said base station comprises a transceiver for receiving alarm activating signals from respective cones or other traffic warning elements having respective transmitters, and for transmitting an alarm activating signal to the respective personal alerting units.

12. A safety system as claimed in any preceding claim fiber comprisingindicator means for indicating the operational status of the system.

13. A safety system as claimed in any preceding claim wherein the or each cone or 10 other warning element and/or personal alerting unit comprises an indicator for indicating its operational status.

14. A safety system as claimed in any preceding claim wherein the operational status of the cone or other element is capable of being remotely monitored by a base 15 station via a wireless communication link.

2 o 16. A traffic cone or like warning element as claimed in Claim 15 wherein the means for generating the alarm signal is a single integral unit capable of being mounted at least partially internally of the cone.

17. A safety system as claimed in Claim 16 wherein the said unit is capable of

being mounted in the apex region of the cone so that a plurality of cones may be stacked in nested configuration in such a way that each cone adds 20% or less of its height to the height of the nested stack.

5 18. An impact alarm apparatus for a traffic cone or other like traffic warning element. 19. A method of detecting movement of approaching vehicles across a visible boundary into a designated safe area; the said method comprising the steps of: 1 o positioning a plurality of traffic cones or like traffic warning elements to provide a visible boundary along a roadside or carriageway boundary between at least one carriageway open for traffic and a traffic free area of a road or roadside verge; each cone or warning element having impact detecting means for detecting an impact with an approaching vehicle, and signal generating means for generating an alarm 5 activating signal in response to a detected impact, and activating the said impact detecting means of each cone or element for monitoring the said boundary.

20. An impact detection apparatus for use in a safety system for alerting roadside personnel to detected incursions by approaching vehicles into designated safe area or 2 o areas; the said system comprising: impact detecting means for attachment to a traffic cone or other warning element for detecting an impact of the cone or element by an approaching vehicle; and, signal generating means for generating an alarm activating signal in response

:3 to a detected impact.

21. An impact detection apparatus for use in a safety system for alerting roadside . personnel to detected incursions by approaching vehicles into designated safe area or 5 areas; the said system comprising: at least one inertia sensor for attachment to a traffic cone or other warning element for detecting an impact of the cone or element by an approaching vehicle; and, a signal processor for processing output signal(s) from the said sensor, the l o signal processor being arranged to compare the said output signal(s) with a pre determined threshold value to determine whether an alarm activating signal is to be generated, a signal generating means for generating an alarm activating signal in response to an alarm activating signal being generated.

22. An impact detection apparatus for use in a safety system for alerting roadside personnel to detected incursions by approaching vehicles into designated safe area or areas; the said system comprising: at least one inertia sensor for attachment to a traffic cone or other warning 2 o element for detecting an impact ofthe cone or element by an approaching vehicle, the inertia sensor(s) are arranged to detect acceleration in a horizontal plane ofthe element or cone only, and a signal generating means for generating an alarm activating signal in response to a detected impact.

23. A safety system substantially as hereinbefore described and with reference to the accompanying drawings.

5

24. A traffic cone or other warning element substantially as hereinbefore described and with reference to the accompanying drawings.