GB2371701A

GB2371701A - Speed trap warning

Info

Publication number: GB2371701A
Application number: GB0211006A
Authority: GB
Inventors: Timothy Michael Rock; Mark David Groves
Original assignee: Origin Technologies Ltd
Current assignee: Origin Technologies Ltd
Priority date: 2000-01-26
Filing date: 2001-01-25
Publication date: 2002-07-31
Anticipated expiration: 2021-01-25
Also published as: GB0211006D0; GB0207928D0; GB2371432A; GB2371701B

Description

2371 70 1

SPEED TRAP DETECTION AND WARNING SYSTEM

This invention relates to a speed trap detection and warning system for alerting the driver of a vehicle to 5 the presence of a nearby speed trap, such as a speed camera, radar gun detector etc. Speed traps of a number of different types are used in increasing numbers by law enforcement authorities around 10 the world. Originally used at accident black spots to cause motorists to reduce speed and therefore reduce accidents, speed traps are now being used in many other locations to generate revenue through speed fines.

15 Speed traps fall into one of two categories; active traps and passive traps.

Active traps work by transmitting a signal towards a vehicle and measuring time delay, Doppler effects or 20 other parameters to measure the speed of the vehicle.

These traps typically use radar or laser light for detection. Examples include Gatso cameras used on UK roads, which record licence plate numbers on film, and digital cameras, which store or transmit licence plate 25 numbers electronically. Active speed traps may operate

from fixed or mobile sites.

Passive traps work by identifying a vehicle at a first position and at a second position. By knowing the 5 distance between the first and second positions and the time taken for the vehicle to travel between the first and second positions, the average speed of the vehicle can be determined. Examples include VASCAR type detectors and SPECS type detectors. Passive speed traps are 10 typically only deployed at fixed sites although some are deployed as mobile units.

A number of methods exist for locating a speed trap. One such method is visual spotting - that is, the driver of 15 a vehicle may see a speed trap as he approaches it. The driver may therefore undertake rapid braking to ensure that his vehicle is travelling at a speed less than the speed limit when it passes the speed trap. This has the problem that undertaking rapid braking is in many 20 circumstances very dangerous and can easily cause accidents. Another method of detecting speed traps is to use an apparatus for detecting radar signals. Such an apparatus 25 works by detecting the radar signals from a radar

operated speed trap and provides an alert that radar signals are incident on the vehicle. Such a system suffers from a number of problems, however. In particular, the driver of a vehicle is only alerted once 5 the radar beam from the speed trap is incident on his vehicle. The driver may therefore undertake extremely rapid braking to ensure that the average speed of his vehicle as detected by the speed trap is below the speed limit. Further, radar detectors will not detect active 10 speed traps using laser light or passive speed traps. Yet further, radar detectors have an additional problem that they may be set off by things other than speed traps which operate on similar frequencies. For example, traffic lights, building alarm systems and petrol 15 stations may trigger a radar detector. The radar detector may therefore provide many false alarms, thereby reducing the usefulness of the detector since it is irritating to the driver and encourages the driver to undertake rapid braking regularly and, from the point of 20 view of other road users, at random.

A further method of detecting speed traps is to detect incident light from active speed traps utilising laser light. As with a radar detector, a laser detector alerts

the driver only when a laser beam is incident on his vehicle, and will not detect speed traps utilizing other detection methods.

5 It is therefore the object of this invention to address one or more of the above problems.

The present invention provides an apparatus as set out in any of claims 1, 2, 4, 5, 6, 9, 10 and 11.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying figures in which: 15 Figure 1 shows a road network in which speed traps are deployed and a vehicle having a speed trap detection and warning system travelling through the road network; Figure 2 shows a perspective view of the speed trap 20 detection and warning system from the vehicle in Figure 1; Figure 3 shows a block diagram of the functional components of the speed trap detection and warning 25 system;

Figure 4 shows a flow diagram of a process for preparing the speed trap detection and warning system for use; 5 Figure 5, which is composed of Figure 5A and Figure 5B, shows a flow diagram of the method of operation of the speed trap detection and warning system in a first operating mode; and 10 Figure 6 shows a flow diagram of the method of operation of the speed trap detection and warning system in a second operating mode.

Referring to Figure 1, a road network 1 comprises a 15 plurality of roads 3 along which a plurality of speed traps 5,6 are deployed. The speed traps take the form of fixed speed traps 5 and a mobile speed trap 6, such as a hand-held radar gun.

20 Driving along the roads 3 is a vehicle 9, which is equipped with a speed trap detection and warning unit 11.

As will be explained in more detail below, the speed trap detection and warning unit 11 has stored within it, among other things, the satellite GPS (Global Positioning 25 System) positions of the fixed speed traps 5 and known

positions where it is common for mobile speed traps 6 to be situated, together with the respective speed limit for the part of the road 3 at which each speed trap 5, 6 is situated, and the direction of travel in which the speed 5 trap is operational (that is, the direction in which each speed trap 5 is pointing to record speeding vehicles, or both directions in the case of a mobile speed trap site 6 since a radar or laser gun can be pointed to detect speeding vehicles in either road direction). The speed 10 trap detection and warning unit 11 uses signals from satellites 7 belonging to the NAVSTAR (NAVigation System with Time And Ranging) GPS system to determine its position, speed and direction of travel (and hence the position, speed and direction of travel of the vehicle 15 9), compares these parameters with the positions, operating directions and speed limits of the speed traps 5,6 stored in its internal database, and provides a warning to the driver of the vehicle 9 when a speed trap 5,6 which is operational in the direction of travel of 20 the vehicle 9 is being approached and the speed of the vehicle 9 exceeds the speed limit at the speed trap 5,6.

The speed trap detection and warning unit 11 is arranged to provide the warning well in advance of the speed trap 5,6 enabling the driver to reduce speed progressively, 25 thereby increasing safety for the driver and other road

users. In addition, as will also be explained below, the speed trap detection and warning unit 11 has stored within it 5 a map of the roads 3 within network 1 together with the respective speed limit for each part of each road. In a second operating mode, the speed trap detection and warning unit 11 uses signals from the satellites 7 to determine the position and speed of the vehicle 9, 10 compares the position and speed with the road map and speed limits stored in its internal database, displays the speed limit to the driver for the road 3 on which he is travelling, and alerts the driver if the speed of vehicle 9 exceeds the speed limit for the road.

Referring now to Figure 2, the speed trap detection and warning unit 11 comprises a display and processing unit 15 and a power connector 17.

20 The display and processing unit 15 comprises an antenna 23 for receiving signals from the satellites 7, processing hardware and memory (not shown in Figure 2, but described below) to process the received signals, a liquid crystal display 25 for displaying information to 25 a user, a speaker 27 for providing audible signals to a

user and input buttons 29 for the input of instructions by a user to control the speed trap detection and warning unit 11. In addition, a telephone lead socket 31 is provided for connecting the speed trap detection and 5 warning unit 11 to a remote database for loading and updating information about, inter alla, the positions of speed traps 5,6, the speed limits thereat and the operational directions thereof as further fixed speed traps 5 are added to the road network 1 and/or as mobile 10 speed traps 6 are used in more locations, and for loading and updating information about the speed limit for each part of each road 3 in the road network 1 as roads are built and/or speed limits on the roads are changed.

15 The power connector 17 comprises an adapter for drawing power from a motor vehicle cigarette lighter socket (not shown). Figure 3 is a block diagram showing the functional 20 elements of the display and processing unit 15.

Referring to Figure 3, the antenna 23 receives signals from the GPS satellites 7 and sends them to a GPS receiver/decoder 41. The GPS receiver/decoder 41 is a 25 conventional component, such as the TrimbleRTH Navigation

Lassen - SK8 Embedded GPS Core Module, which processes the received GPS signals and outputs what is known in the art as a "navigation solution", which comprises a data stream defining the position, speed and direction of 5 travel of vehicle 9.

The navigation solution from the GPS receiver/decoder 41 is passed to a central processing unit (CPU) 43 which operates according to instructions stored in an operating 10 instruction store 45 to perform processing as will be described below. Working memory 51 is provided for the CPU 43 to use while performing processing.

The GPS positions of the fixed speed traps 5 and known 15 positions at which it is common for a mobile speed trap 6 to be situated are stored in a first database store 49.

Also stored in first database store 49 in this embodiment is data defining the respective road speed limit at each speed trap location, the type of each speed trap (that 20 is, the detection method by which it operates and/or whether it is a fixed or a mobile site), the direction of travel in which each speed trap is operational and the number of the road on which each speed trap is located.

In addition, data is stored in the first database 49 25 defining a telephone number to be used by the CPU 43 for

updating the database contents (as described later).

A second database store 50 is provided for storing data for use in a second operating mode of the speed trap 5 detection and warning unit 11. Stored in the second data base store 50 is data describing the GPS positions for every road 3 in a selected road network 1, and the data describing the respective road speed limit on each part of each road. Also stored in the second database store 10 50 in this embodiment is data defining the road number of each road in the network.

As will be described below, in use, CPU 43 compares the navigation solution in the data from the GPS 15 receiver/decoder 41 with the data from the first database store 49 or the second database store 50, and displays information to the driver of the vehicle 9 via the display 25 and/or generates an audible alert through the speaker 27.

Input buttons 29 are provided for the user to select the operating mode of the speed trap detection and warning unit 11, and to change operating parameters such as the volume of audible alerts and the information to be 25 displayed on the screen. In addition, a button is

provided for initiating a function (described below) to update the data stored in the first database store 49 and the second database store 50. The update function makes use of a system ID which is unique for each speed trap 5 detection and warning unit 11 and which is stored in a system ID store 47.

A telephone interface 53 is provided for connecting with a remote database 55, which is not a part of the speed 10 trap detection and warning unit 11, via the telephone lead socket 31. That is, a cable (not shown) is used to connect between the telephone lead socket 31 and a telephone network (not shown) so as to connect the speed trap detection and warning unit 11 to a remote database 15 55 which is also connected to the telephone network. The remote database 55 stores data for storage in the first database store 49 defining the position of each speed trap 5,6 the road number of the road 3 on which each speed trap is located, the speed limit of the road 3 for 20 the position at which the speed trap is located, the operating direction(s) of each speed trap and the type of speed trap. In addition, remote database 55 stores data for storage in the second database store 50 defining the positions of each road 3 in the road network 1, the 25 road number of each road 3 and the speed limit for each

part of each road 3. The data in database 55 is updated when an additional fixed speed trap 5 is added to the road network 1, when an additional site at which a mobile speed trap 6 is frequently used becomes known, when new 5 roads are added to the road network 1 or when the speed limit for an existing road is changed. The telephone interface 53 allows the CPU 43 to execute the update database function to use information from the remote database 55 to replace the data stored in the first 10 database store 49 and the second database store 50.

The processing operations of the speed trap detection and warning unit 11 will now be described.

15 The operation to load data into, or update data in, database store 49 and second database store 50 will be described first with reference to Figure 4.

In Figure 4, all functions on the left-hand side of the 20 dotted line are functions performed by the speed trap detection and warning unit 11 and all functions on the right-hand side are functions performed by the remote database 55.

25 In step S4-1 the speed trap detection and warning unit

11 establishes connection with the remote database 55.

In this step, the speed trap detection and warning unit ll dials the telephone number of the remote database 55 which is stored in the first database store 49 within the 5 speed trap detection and warning unit 11, and conventional "handshaking" techniques are used to establish connection.

In step S4-3, once connection between the speed trap lO detection and warning unit 11 and the remote database 55 has been established, the speed trap detection and warning unit 11 transmits the system ID stored in system ID store 47 to the remote database 55.

15 In steps S4-5 and S4-7 the remote database 55, upon receiving the system ID from the speed trap detection and warning unit 11, checks the status of the received system ID and determines whether the speed trap detection and warning unit 11 having that particular system ID is 20 entitled to receive an update. In this embodiment, a particular speed trap detection and warning unit ll is barred from receiving an update if that unit has been reported stolen or if the owner of the unit has not paid the subscription fee necessary for the owner to receive 25 database data.

If it is determined at step S4-7 that the speed trap detection and warning unit 11 is not to receive an update, an error message is transmitted in step S4-9.

Upon receiving such an error message, at step S4-11 the speed trap detection and warning unit 11 displays an error message to the user on the display 25 so that the user is aware that he is not receiving an update. The 10 user can then take appropriate action, such as contacting the provider of the remote database 55 to arrange for his entitlement to receive an update to be restored.

Following display of the error message the update database function then ends.

On the other hand, if it is decided at Step S4-7 that the speed trap detection and warning unit 11 is entitled to receive an update, then the new database data is transmitted at step S4-13. The new database data 20 transmitted comprises a complete set of up-to-date GPS positions of all known fixed speed traps 5 and positions where it is common for mobile speed trap 6 to be situated, together with the road speed limit at all the positions, the type of speed trap, the operational 25 direction of each speed trap, and the road number on

which each speed trap is located. The new database data further comprises the GPS positions of all roads and the speed limit on each part of each road. The new database data also comprises all telephone numbers on which the 5 remote database 55 may be accessed such that in the event of any new telephone phone numbers being added or any numbers being for any reason unavailable, the speed trap detection and warning unit 11 will still be able to access the remote database 55 next time an update is 10 required.

Upon receiving the new database data, in step S4-15 the speed trap detection and warning unit 11 stores the new database data in the first and second database stores 49 15 and 50 to replace the existing data.

Once all of the new database data has been stored in the first and second database stores 49 and 50, in step S4-17 the speed trap detection and warning unit 11 displays an 20 update complete message to the user on the display 25.

The update database function then ends and the speed trap detection and warning unit is ready for use.

Although the update database function has been described 25 in the context of preparing the speed trap detection and

warning unit 11 for first use, the function is also used to update the contents of the database 49 to 50 to ensure that up-to-date databases are being used.

5 The operation of the speed trap detection and warning unit 11 in warning the driver of vehicle 9 of one or more approaching speed traps 5, 6 will now be described with reference to Figure 5.

10 In step S5-1 the GPS receiver/decoder 41 generates a navigation solution and transmits it to the CPU 43. The CPU 43 then extracts from the navigation solution the current speed at which the speed trap detection and warning unit 11 (and hence the vehicle 9) is travelling, 15 the position of the vehicle 9 and the direction of travel of the vehicle 9.

At step S5-2 the CPU 43 checks to determine whether a navigation solution has been generated. A navigation 20 solution may not be generated for example whilst the vehicle 9 is within a road tunnel, or if landscape or architectural features prevent the GPS receiver/decoder 41 from receiving enough satellite signals to generate a navigation solution. In addition, 25 when the speed trap detection and warning unit 11 is

first switched on after a period of non-operation, the GPS receiver/decoder 41 may require up to a few minutes to generate a first navigation solution. If it is determined at step S5-2 that no navigation solution has 5 been generated, then at step S5-3 the CPU 43 causes a warning to be displayed on display 25 and the process returns to step S51. On the other hand, if it is determined at step S5-2 that a navigation solution has been granted, then the process continues to step S5-4.

At step S5-4 the CPU 43 causes the current vehicle speed to be displayed on the display 25. The current vehicle speed continues to be displayed on the display 25 until, on a future cycle, the speed is determined to have 15 changed, at which time the display 25 is updated to display the new current vehicle speed. Accordingly, the display of the current vehicle speed on the display 25 is updated continuously in accordance with the operational cycle rate.

At step S5-5 the CPU 43 compares the current location of the vehicle 9 as determined from the navigation solution at step S5-1 to the stored locations of speed trap sites stored in the first database store 49.

At step S5-7 CPU 43 determines whether any speed traps sites are within a first predetermined distance of the vehicle 9, which, in this embodiment is set to 500 metres. If no speed trap sites are within the first 5 predetermined distance of the vehicle 9, processing returns to step S5-1 and a new navigation solution is processed. On the other hand, if it is determined at step S5-7 that 10 one or more speed trap sites are within the first predetermined distance of the vehicle 9, then, at step S5-9, the direction of travel of the vehicle 9 (previously determined at step S5-1) is compared to the location of the speed trap site(s) identified at steps 15 S5-5 and S5-7.

At step S5-11, CPU 43 determines whether or not the vehicle is travelling towards any of the speed trap sites within the first predetermined distance of the vehicle.

If the vehicle 9 is not travelling towards a speed trap site, it is still necessary to monitor the speed of the vehicle 9 after the speed trap has been passed if the vehicle is still within the operating range of the trap, 25 since the trap may still detect a speeding vehicle within

this range. Therefore, to take account of this at step S5-12, CPU 43 determines whether the vehicle is still within a second predetermined distance of the speed trap site. The second predetermined distance represents the 5 range over which the speed trap may operate, and, in this embodiment, is set to 100 metres, and this second distance test is performed as many speed trap devices actually detect speeding vehicles when the vehicle is at a position past the speed trap.

If it is determined at step S5-12 that the vehicle 9 is beyond the second predetermined distance of the speed trap site then the process returns to step S5-1 and a new navigation solution is processed.

On the other hand, if it is determined at step S5-11 that the vehicle is travelling towards the speed trap site or it is determined at step S5-11 that the vehicle is not travailing towards the speed trap site but it is 20 determined at step S5-12 that the vehicle is still within the second predetermined distance of the speed trap site, then the process proceeds to step S5-13.

In step S5-13, the CPU 43 compares the direction of 25 travel of the vehicle 9 to the direction in which the

speed trap is operational. This comparison is to ensure that the driver of the vehicle 9 is not alerted when the vehicle 9 is approaching a speed trap which cannot trap the vehicle 9 because the trap is directed or positioned 5 to trap vehicles which are approaching the speed trap from a direction different to the direction of travel of the vehicle 9.

In step S5-14, CPU 43 determines whether the vehicle 9 10 is travelling in a direction in which the speed trap is operational. If it is determined at step S5-14 that the vehicle 9 is not travailing in the direction in which the speed trap 15 is operational, the process returns to step S5-1 and a new navigation solution is processed. On the other hand, if it is determined at step S5-14 that the vehicle 9 is travelling in the direction in which the speed trap is operational, then the process proceeds to step S5-15.

In step S5-15 the speed of travel of the vehicle 9 (previously determined at step S5-1) is compared to the stored speed limit at the speed trap site stored in database store 49. It is then determined at step S5-17 25 whether the speed of travel of the vehicle 9 is greater

than the speed limit at the speed trap site.

If the speed of travel is determined to be less than the speed limit of the speed trap site then the process 5 returns to step S5-1 and a new navigation solution is processed. On the other hand, if it is determined at step S5-17 that the speed of travel of the vehicle 9 is greater than the 10 speed limit at the speed trap site, then at step S5-19 CPU 43 causes an audible alarm to be emitted from the speaker 27 and causes the speed limit, type of speed trap and road number at the speed trap site to be displayed on display 25 so that the user can compare his current 15 speed, as displayed on the display 25 in step S5-4, to the speed limit at the speed trap site and adjust the speed of the vehicle 9 accordingly. The process then returns to step S5-1 and a new navigation solution is processed. Because speed trap detection and warning unit 11 tests at step S5-7 whether the vehicle is within a relatively large distance of a speed trap 5,6 (500 metros in this embodiment), the driver of vehicle 9 is given an early 25 warning that it is approaching a speed trap and therefore

has plenty of time to reduce the vehicle speed gradually and safely.

The speed trap detection and warning unit 11 may be 5 utilised in areas where many mobile speed traps 6 are deployed at sites which change regularly. Thus the first database 49 of regular sites is of reduced utility. To address this, and also the case where the data in the first database store 49 has not been updated for a long 10 time (and hence may be out-of-date), a second operating mode of the speed trap detection and warning unit 11, additional to the first operating mode described above, is provided in this embodiment. The second operating mode is selected using one of the input buttons 29, and, as 15 will be described below, in the second operating mode the user of the unit is warned whenever the vehicle in which the unit is installed exceeds the speed limit for the road along which the vehicle is travelling.

20 The second operation mode is described in detail in Figure 6.

In steps S6-l to S6-4, GPS receiver/decoder 41 generates a navigation solution and CPU 43 determines whether a 25 navigation solution has been generated and if not

displays a warning, or if so causes the current speed of the vehicle 9 to be displayed on display 25 as described for steps S5-1 to S5-4 of Figure 5.

5 At step S6-5, the current location and the current direction of travel and recorded values for recent direction of travel generated in previous iterations of step S6-1 are compared to the data stored in second database store 50 defining the location of all roads 10 within the relevant road network 1 and the speed limits which apply to each road, to determine the current road and part thereof on which vehicle 9 is travelling.

The current location and current direction of travel are 15 used at step S6-5 together with recorded values (stored in working memory 51) for recent direction of travel because the navigation solution from the GPS receiver/decoder 41 may include errors in the data describing the current position of the vehicle 9, and 20 thus where roads are very close together it may be difficult to determine the current road on which vehicle 9 is travelling on the basis of current position and current direction of travel information only.

25 At step S6-7, CPU 43 determines whether it is possible

to identify the current road on which vehicle 9 is travelling. If it is not possible to determine the current road, then CPU 43 causes a warning to be displayed on display 25 at step S6-9 and the process 5 returns to step S6-1 and a new navigation solution is processed. On the other hand, if it is possible to determine the current road, then the current road is identified and the 10 process continues to steps S6-11 and S6-13, in which, CPU 43 compares the speed of travel of the vehicle 9 to the speed limit of the current road stored in the second database store 50.

15 If it is determined at step S6-13 that the speed of travel is less than the speed limit of the current road, then the process returns to step S6-1 and a new navigation solution is processed.

20 On the other hand, if it is determined at step S6-13 that the current speed of travel is greater than the speed limit of the current road, then, at step S6-15, CPU 43 causes an audible alarm to be emitted from the speaker 27 and causes the speed limit and road number for the 25 current road to be displayed on the display 25. Thus,

the driver of vehicle 9 is then able to compare his current speed, as displayed in accordance with step S6-4, with the speed limit for the current road and adjust his speed accordingly. The process then returns to step S6-1 5 and a new navigation solution is processed.

Many modifications are possible to the embodiment described above.

10 For example, in order to provide information to the user about mobile sites utilising radar traps or laser light traps and fixed sites usingradar traps and laser light traps which are not included in the database, it is possible to combine the speed trap detection and warning 15 unit 11 described above with conventional radar and laser light detectors. However, the addition of such detector would re-introduce the problems of last minute warnings for speed traps not included in the database, and the possibility of false alarms from the radar detector.

The speed trap processing and detection unit 11 is not limited to utilising GPS for obtaining navigation solutions. Any radionavigation system providing sufficient accuracy in determining position may be 25 utilised. For example, GLONASS (the Russian equivalent

to GPS) or GNSS (a proposed new satellite new navigation system) could both be used instead of GPS to provide a navigation solution.

5 In the above embodiment, the display 25 is described as a liquid crystal display. Alternatively, the display 25 may take the form of a light emitting diode (LED) dot matrix, an array of figure-of-eight LED displays or any other type of display device.

In the above embodiment, it is described with reference to Figure 4 to issue an update to a speed trap detection and warning unit 11 if a system ID is determined to belong to a set of system IDs for which a subscription fee has been paid As an alternative, the remote database 55 may operate to receive a credit card number from the speed trap detection and warning unit 11 or a user. The remote database would then contact an appropriate clearing authority to establish whether the given credit 20 card number is valid and chargeable. If it is determined that the credit card number is valid, an update will be issued as described in steps S4- 13 to S4-17, and if not, an error message will be transmitted as described in steps S4-9 and S4-11.

In the above embodiment, it is described with reference to Figure 4 that the data in both the first and second database stores 49,50 are updated during an update function by connection to a remote database 55. It is 5 also possible to update the data in only one database at a time, for example if only one database requires updating, as would likely occur because the positions of speed traps 5,6 are likely to change more often than the layout and speed limits of roads in a road network 1.

For the above embodiment, it is described with reference to Figure 5 that the first predetermined distance is set to 500 metros. However, this distance may be set to any value which provides adequate notice that the vehicle 9 15 is approaching a speed trap.

In the above embodiment, it is described with reference to Figure 5 that the second predetermined distance is set to 100 metres. However, this distance may be set to any 20 value which exceeds the typical operating range of a speed trap.

In the above embodiment, it is described with reference to Figure 5, to perform a check on a second predetermined 25 distance in step S5-12. However, this step may be

omitted as the driver of the vehicle 9 will likely be aware that a typical speed trap 5,6 detects speeding vehicles at a position past the speed trap.

5 In the above embodiment it is described with reference to Figure 5 that when a vehicle 9 is approaching a speed trap 5,6 that the current speed of the vehicle and the speed limit of the speed trap are output to the display 25 by the CPU 43. It is additionally possible for the 10 CPU 43 to calculate the distance to the speed trap site 5,6 and display the calculated distance on the display 25 at step S5-19 so that the driver of the vehicle 9 can judge how swiftly he needs to slow the vehicle 9.

15 In the above embodiment, it is described with reference to Figure 6 that the current location and current direction of travel are used together with recorded values for recent direction of travel in the comparison with the data from the second database store 50 to 20 determine the current road. However, if it is found that the current location and current direction of travel provide sufficiently accurate data to determine the current road, then the recorded values for recent direction of travel may be omitted.

Although, it has been described in the above embodiment to provide a speed trap detection and warning system having two operating modes, the second operating mode (as described with reference to Figure 6) may be omitted.

5 In the case that the second operating mode is omitted, the second database store 50 is also omitted.

Although it has been described in the above embodiment with reference to Figure 5 to display the road number of 10 the road 3 on which the vehicle 9 is travelling at step S5-19, this is not essential to the operation of the invention and may be omitted.

In the above embodiment, it has been described to store 15 the telephone number for the remote database 55 in the first database store 49. However, this number may alternatively be stored in the second database store 50 or in a further separate store.

20 In the above embodiment, it is described to use the input buttons 29 to adjust the volume of audible alerts to be emitted from speaker 27. It is further possible to provide a mute function such that audible alerts can be switched OFF completely. It is also possible to provide 25 a function such that, the first time that an audible

alert is emitted with respect to a given speed trap 5,6, the alert is emitted at a first volume, and all further audible alerts with respect to the given speed trap 5,6 are emitted at a second volume.

In the above embodiments, it has been described with reference to Figures 5 and 6 to display the current calculated vehicle speed at steps S5-4 and S6-4. It is additionally possible to display the current direction 10 of travel of the vehicle 9 at either or both of those steps in addition to the current speed.

It is also possible to provide a function for adding a speed trap to the database contained in the speed trap 15 detection and warning system manually. The user would be required to press a button 29 on the speed trap detection and warning unit 11 as the vehicle 9 is driven past a speed trap site which is not already stored in the first database store 49. The user would also enter the 20 speed limit at the speed trap, the direction of operation of the speed trap and the number of the road on which the speed trap is located. These data would be stored both for use by the speed trap detection and warning system and for uploading to the remote database 55 as part of 25 the update function.

Claims

1. A speed trap detection and warning apparatus for a vehicle, comprising: 5 satellite signal processing means for receiving satellite signals and for processing the received signals to generate location data defining the location of the apparatus; storage means configured to store data defining the 10 respective location of each of a plurality of speed traps; means for comparing the location determined from the satellite signals with the stored speed trap locations to determine whether the vehicle is within a 15 predetermined distance of a speed trap; alerting means for alerting a user to the presence of a speed trap if it is determined that the apparatus is within a predetermined distance of a speed trap; and a telephone interface directly coupleable by a cable 20 to a telephone line which is part of a telephone network to permit data transfer over the telephone network between a remote database connected to the telephone network and the apparatus to transfer data defining the locations of speed traps from the remote database to the 25 apparatus for storage in the storage means;

wherein the apparatus further comprises: means for connecting the apparatus to a power supply of the vehicle to power the apparatus.

5

2. A speed trap detection and warning apparatus for a vehicle, comprising: satellite signal processing means for receiving satellite signals and for processing the received signals to generate location data defining the location of the 10 apparatus; storage means configured to store data defining the respective location of each of a plurality of speed traps; means for comparing the location determined from the 15 satellite signals with the stored speed trap locations to determine whether the vehicle is within a predetermined distance of a speed trap; alerting means for alerting a user to the presence of a speed trap if it is determined that the apparatus 20 is within a predetermined distance of a speed trap; and a telephone interface directly coupleable by a cable to a telephone line which is part of a telephone network to permit data transfer over the telephone network between a remote database connected to the telephone 25 network and the apparatus to transfer data defining the

locations of speed traps from the remote database to the apparatus for storage in the storage means; wherein the apparatus further comprises: a connector for releaseably receiving the cable to 5 connect the apparatus to the telephone line.

3. An apparatus according to claim 2, further comprising: a housing having the alerting means and the 10 connector on different faces thereof.

4. A speed trap detection and warning apparatus for a vehicle, comprising: satellite signal processing means for receiving 15 satellite signals and for processing the received signals to generate location data defining the location of the apparatus; storage means configured to store data defining the respective location of each of a plurality of speed 20 traps; means for comparing the location determined from the satellite signals with the stored speed trap locations to determine whether the vehicle is within a predetermined distance of a speed trap; 25 alerting means for alerting a user to the presence

of a speed trap if it is determined that the apparatus is within a predetermined distance of a speed trap; and a telephone interface directly coupleable by a cable to a telephone line which is part of a telephone network 5 to permit data transfer over the telephone network between a remote database connected to the telephone network and the apparatus to transfer data defining the locations of speed traps from the remote database to the apparatus for storage in the storage means; 10 wherein the apparatus further comprises: storage means storing identification data identifying the apparatus; and wherein the apparatus is operable to transmit the identification data to the remote database when the 15 apparatus is connected to the telephone line.

5. A speed trap detection and warning apparatus for a vehicle, comprising: satellite signal processing means for receiving 20 satellite signals and for processing the received signals to generate location data defining the location of the apparatus; storage means configured to store data defining the respective location of each of a plurality of speed 25 traps;

means for comparing the location determined from the satellite signals with the stored speed trap locations to determine whether the vehicle is within a predetermined distance of a speed trap; 5 alerting means for alerting a user to the presence of a speed trap if it is determined that the apparatus is within a predetermined distance of a speed trap; and a telephone interface directly coupleable by a cable to a telephone line which is part of a telephone network 10 to permit data transfer over the telephone network between a remote database connected to the telephone network and the apparatus to transfer data defining the locations of speed traps from the remote database to the apparatus for storage in the storage means; 15 wherein the apparatus is operable to replace existing data stored in the storage means with data received via the telephone network from the remote database. 20

6. A speed trap detection and warning apparatus for a vehicle, comprising: satellite signal processing means for receiving satellite signals and for processing the received signals to generate location data defining the location of the 25 apparatus;

storage means configured to store data defining the respective location of each of a plurality of speed traps; means for comparing the location determined from the 5 satellite signals with the stored speed trap locations to determine whether the vehicle is within a predetermined distance of a speed trap; alerting means for alerting a user to the presence of a speed trap if it is determined that the apparatus 10 is within a predetermined distance of a speed trap; and a telephone interface directly coupleable by a cable to a telephone line which is part of a telephone network to permit data transfer over the telephone network between a remote database connected to the telephone 15 network and the apparatus to transfer data defining the locations of speed traps from the remote database to the apparatus for storage in the storage means; wherein the apparatus further comprises: means actuable by a user to control an output 20 characteristic of the alerting means.

7. An apparatus according to claim 6, wherein: the altering means comprises a speaker; and the means actuable by a user to control an output 25 characteristic of the altering means comprises means for

changing the volume of the sound output of the speaker,

8. An apparatus according to claim 6, wherein: the alerting means comprises a speaker; and 5the means actuable by a user to control an output characteristic of the alerting means comprises means for muting the sound output of the speaker.

9. A speed trap detection and warning apparatus for a lovehicle, comprising: satellite signal processing means for receiving satellite signals and for processing the received signals to generate location data defining the location of the apparatus; 15storage means configured to store data defining the respective location of each of a plurality of speed traps; means for comparing the location determined from the satellite signals with the stored speed trap locations 20to determine whether the vehicle is within a predetermined distance of a speed trap; alerting means for alerting a user to the presence of a speed trap if it is determined that the apparatus is within a predetermined distance of a speed trap; and 25a telephone interface directly coupleable by a cable

to a telephone line which is part of a telephone network to permit data transfer over the telephone network between a remote database connected to the telephone network and the apparatus to transfer data defining the 5 locations of speed traps from the remote database to the apparatus for storage in the storage means; wherein the apparatus further comprises: a cable for connecting the apparatus to a power supply to power the apparatus; and 10 a housing having the alerting means and the outlet for the cable on different faces thereof.

10. A speed trap detection and warning apparatus for a vehicle, comprising: 15 satellite signal processing means for receiving satellite signals and for processing the received signals to generate location data defining the location of the apparatus; storage means configured to store data defining the 20 respective location of each of a plurality of speed traps; means for comparing the location determined from the satellite signals with the stored speed trap locations to determine whether the vehicle is within a 25 predetermined distance of a speed trap;

alerting means for alerting a user to the presence of a speed trap if it is determined that the apparatus is within a predetermined distance of a speed trap; and a telephone interface directly coupleable by a cable 5 to a telephone line which is part of a telephone network to permit data transfer over the telephone network between a remote database connected to the telephone network and the apparatus to transfer data defining the locations of speed traps from the remote database to the 10 apparatus for storage in the storage means; wherein the apparatus further comprises: control means actuable by a user to control the apparatus, and a housing having the alerting means and control 15 means arranged on the same face thereof.

11. A speed trap detection and warning apparatus for a vehicle, comprising: satellite signal processing means for receiving 20 satellite signals and for processing the received signals to generate location data defining the location of the apparatus; storage means configured to store data defining the respective location of each of a plurality of speed 25 traps;

means for comparing the location determined from the satellite signals with the stored speed trap locations to determine whether the vehicle is within a predetermined distance of a speed trap; 5 alerting means for alerting a user to the presence of a speed trap if it is determined that the apparatus is within a predetermined distance of a speed trap; and a telephone interface directly coupleable by a cable to a telephone line which is part of a telephone network 10 to permit data transfer over the telephone network between a remote database connected to the telephone network and the apparatus to transfer data defining the locations of speed traps from the remote database to the apparatus for storage in the storage means; 15 wherein: the satellite signal processing means is operable to process the received signals to calculate the speed of travel of the vehicle; the storage means is configured to store data 20 defining the respective road speed limit at the location of each of the speed traps; the apparatus further comprises means for comparing the calculated speed of the vehicle with the stored road speed limit data to determine whether the vehicle is 25 travelling at a speed above the road speed limit at a

speed trap; and the alerting means is controlled, in use, to alert the user if it is determined that the vehicle is within a predetermined distance of a speed trap and also that 5 the vehicle is travelling at a speed greater than the road speed limit at the speed trap.

12. An apparatus according to any preceding claim, wherein the apparatus has stored therein data defining 10 a telephone number, and the telephone interface is operable to dial the telephone number automatically when the apparatus is connected to the telephone network to establish a telephone connection with the remote database.

13. An apparatus according to any of preceding claim, further comprising a manually operable actuator which causes the current position of the apparatus to be stored therein when actuated.

14. An apparatus according to any preceding claim, wherein the alterting means comprises a display.