GB2173331A - Vehicle safety systems - Google Patents

Abstract

As most broadly claimed the invention includes:- (i) a roadside installation for determining the prevailing visibility and for visibly indicating a recommended safe speed on motorway warning signs (ii) a vehicle mounted installation for determining the range of an object in front of the vehicle and for indicating to the driver the range so determined. The vehicle mounted installation may also activate vehicle controls to slow the vehicle if a condition deemed to be dangerous is detected. <IMAGE>

Description

SPECIFICATION Motorways' automatic speed restriction lamps, and vehicle spacing equipment The number of deaths and vehicle destructions can be alleviated.by drivers properly following instrument warning signals and speed restrictions imposed by an automatic warning system installed on motorways and other highways. It is an object of this invention to provide a means for warning drivers whenever safe braking distances are eroded between the driver's vehicle and the vehicle in front, especially during periods of poor visibility.

According to the present invention, there is provided in a vehicle, Radar Detection Equipment, and Sonar Ranging equipment, and means for determining the rate of closing on the vehicle in front, whenever such clearance distance is eroded.

Yet another objective of this invention is the provision of an automatic motorway speed restriction system, applicable to the entire motorway's system, which operates 24 hours per day, and provides a speed restriction display relating the restriction to prevailing ambient visibility. For a better understanding of the invention reference will now be made by way of example, to the accompanying drawings, and diagrams, in which: Figure 1, is a block diagram showing how the motorway automatic speed restriction lamps function.

Figure 2, discloses a flow chart illustrating the operation of an onboard mini-computer used in Vehicle Spacing Equipment.

Figure 3, discloses a Doppler Radar Detection system proposed in a Patent Specification No 1,330,879 and presented to illustrate how the present invention differs from the prior art Figure 4, discloses the electronic circuit of the present invention, and illustrates the improvements on the prior art.

Figures 5, and 6, are provided only for the reader's better understanding, of discrete part circuits, and how they function in the electronic circuit, provided by the printed circuit board.

Fig. 1, illustrates a typical arrangement of how the motorway automatic speed restriction lamps function, to which the following reference numbers apply: 1. Light source, housed in weather proof case, with window.

2. Light beam passing through prevailing visibility conditions but surrounded by two concen tric tubes with holes that allow air to pass into the light beam but exclude aircorne pollution such as carbon.

3. Light meter in weather proof case, which measures the gain or loss in luminosity, in which the digital output is coupled to the mini-computer.

4. Dedicated mini-computer in weather proof case which correlates visibility in lumens with safe motorway speed by interpolating from the stored look-up tables in the Read Only Memory (ROM). Such tables may be programmed in the form of a mathematical formula.

5. Power actuator, which converts the signals from the mini-computer into power pulses which switches on the appropriate light bulbs within the display bezel, to give the appro priate speed restriction.

6. Motorway speed restriction matrix display lamp.

The light meter embodies a photodiode contained in a case with a window. When reverse biased the leakage current increases proportionately to the incident light, and is used in photometers, modulated light detectors, or for high speed counting in punched card tape readers, having a response time 250 n.sec. The light source is housed separately in a hermetically sealed container, and will generate sufficient heat to prevent misting on the window. The other components are housed in another container with small heater and thermostat to control the working environment, in order to maintain them within the specified limits. Existing motorway speed restriction lamps need no modification for the control system to work satisfactorily. All such component parts required for the control system can be purchased off-the-shelf.The power actuator comprises a relay control box, and this together with the speed restriction lamps requires a separate power supply, to that of the dedicated mini-computer and light meter.

Recent developments in sonar rangers may make them a useful alternative to the highly sophisticated radar ranger described in this document. Briefly such ranging devices embody an automatic gain control system, which samples the amplitude of the return echo, and programs the receiver gain to maintain constant echo amplitude, regardless of any variation in target reflectivity and air path attenuation caused by varying ambient conditions. Such a measuring device consists of two high efficiency transducers, and associated electronic circuitry, in which the time required for an ultrasonic pulse, and reflected echo takes to reach the object and return is measured. Since each pulse travels at essentially constant speed in air, the analogue signal is directly proportional to the distance.Spurious electrical and acoustic noise presents no problem, even in the hostile environment of vehicle instrumentation. One system available has a range of 200 ft, and is accurate to within 1% if fitted with a temperature compensator. The tone decoder or diode detector places a window about the echo received from a target, and hence other real but unwanted echos are ignored, and is ideal for harsh environments. The analogue output is easily converted to a L.E.D. read-out. These ultrasonic rangers have a unique two-stage acoustic matching system for high attentuation environments which embody ultrasonic transducers consisting of barium titanate crystals within a CPVC housing, with optional face covering.Such 'flexural mode' transducers. are self-cleaning, in action, which ensures reliable no-maintenance operation in high dust areas, and are uneffected by moisture or steam. Such a ranger may be used in conjunction with a dedicated mini-computer, or as an adjunct with the radar detector system. In the latter case one instrument will check the other instrument reading, using the computer's comparator, or the sonar ranger may be used to calibrate the radar ranger and determine any instrument error constant that will require automatic correction.

CARRYING OUT INVENTION Referring to Fig. 1; it will be necessary to pass the light beam 2 through two concentric pipes in which holes are drilled around the periphery through which ambient air can pass freely but which prevent the intrusion of carbon particles, dust and other motorway air pollution which otherwise may form on the instrument lenses and obstruct their line of sight to give false readings. Two tubes will perform this function provided the holes are oriented in such a way that no two holes permit direct access to the light beam. Moreover each end of the tubes should be designed to have solid walls for a length of say 20 cms. This will prevent the ingress of rain water, and more importantly keep out daylight or headlamp incident light which would also effect the accuracy.

Referring to Fig. 3; which discloses a Doppler Radar detection system proposed in United States of America, Patent No. 1,330,879 UK but modified by the present Application to incorporate a microprocessor, with digital display of the distance between vehicles, and the use of a transponder attached to the rear of the vehicle in front. The latter item is recommended but not essential to make the system work. The power supply 1 from the vehicle's 12 volts ignition supplies a bias voltage which excites an impatt oscillator 2, which provides RF energy, most of which is fed into a transmitter antenna 3. The transmitter antenna and receiver antenna 4 are positioned adjacent to the headlamps. These antennas are highly directive so that they transmit energy and sense energy received from a relatively small angular sector directly in front of the vehicle.In this manner the radar system discriminates against obstacles or traffic in adjoining traffic lanes, or on the hardshoulder. They embody small backing radar dishes which will be pointed downwards so that the signals strike the surface of the carriageway at a distance of 150 metres ahead of the vehicle, being the maximum distance to which it is practical to operate detection. But any vehicle or obstacle in front within 100 metres will reflect the transmitted energy back to the vehicle where it is picked up on the receiver antenna 4. The received energy is fed into a four terminal microwave device called a magic tee 5, comprising an H arm tee, whilst some of the RF energy is coupled directly to the magic tee by means of a -20 db directional coupler 5.The tee is an asymmetrical magic tee i.e; the RF energy propogated down each side arm have a unique phase shift with respect to each other. In a symmetrical magic tee the signals in each side arm are out of phase by exactly 180 degrees. The asymmetrical tee produces a phase relationship, the sign of the phase shift depends on whether the received frequency is higher or lower than the transmitted frequency. If the vehicle clearance distance is decreasing then the received frequency will be higher than the transmitted frequency, and vise versa. i.e; if the clearance distance is increasing then the received energy frequency will be lower. The former case is known as closing Doppler, and the latter case is known as opening Doppler.The difference in frequency between the transmitted signal and the received frequency is directly proportional to the relative velocity between the vehicle and the obstacle. In each arm of the asymmetrical magic tee there exists two RF signals - the sending RF and the receiving RF which have a unique phase relationship, which is preserved in the detection circuit, a description of which follows.

Briefly, conventional square law high frequency microwave crystal detectors, 6 and 7, are connected to the two magic tee side arms. The components of the detector outputs are high frequency except for the difference between the transmitted frequency and received frequency which is the relatively low Doppler frequency. The outputs of the two detectors are fed through Lo-pass filters 10 and 11, to separate amplifiers 12 and 13 on lines 8 and 9. If an obstacle in front of the vehicle has a different velocity to the vehicle, then there will be present on lines 8 and 9 signals of relatively low frequency which are directly proportional to the relative velocities of the vehicle and the obstacle. The unique phase relationships are neither 0 deg or 180 deg but either positive or negative, depending on whether it is opening or closing Doppler.

The purpose of the Lo-pass filters is to pass only low frequency Doppler frequencies. For example if the transmitted frequency is 10.5 ghz then the maximum Doppler frequency will not exceed 3500 hz for a 140 mph relative velocity. These low pass filters reject any frequencies that are not Doppler-generated and this includes spurious noise generated electrical signals. The amplifiers are conventional feed-back to provide a voltage gain of approx 200. The operational amplifiers receive a bias voltage of plus or minus 1 5V from the power supply. Voltage limiters are provided in order not to overload the the second stage of amplification 16 and 17. A differentiator circuit 18 is provided to produce a single positive voltage spike for each complete Doppler voltage cycle.A one-shot circuit 19, is provided such that the sharp spikes at the input will cause a square positive pulse of constant time duration at the output, which is directly proportional to the value of the capacitor (not shown) in the circuit. In addition a NPN transistor is used as part of the circuit. Such a transistor will not conduct unless there is a negative potential in the base with respect to the emitter, which is the case when there is closing Doppler cycles. i.e; when the vehicles are decreasing their clearance distance. Thus the circuit discriminates between opening and closing Doppler signals. A count down capacator 20, discriminates between false targets such as vehicles in adjacent lanes, road traffic signs and so on, which appear in the field of view for a relatively short period of time.When the output of the capactor reaches the threshold of the uni-junction transistor 21, a spiked pulse will start charging the transistor until it fires. Thus a certain degree of false target discrimination is accomplished. A second one-shot circuit 22, generates a positive-going-square-pulse which actuates the driver 23, which is simply a transistor switch, which is normally closed, but when open provides a conductive path to earth the audio oscillator 24, which in turn causes the loudspeaker 25 to emit an audible signal to serve as a warning to the vehicle driver.

The impatt oscillator shown in Fig. 4, transmits an unmodulated pulsed electro-magnetic signal having a fixed very high frequency (VHF) of 10.5 GHz (G=giga=109) and if the maximum relative velocity to be detected is 140 mph then the Doppler frequency is only 3500 Hz which is insignificant with the present invention, in relation to the transmitted VHF. The present invention detects the elapsed time between sending the pulsed signal and receiving part of the pulse of frequency cycles by synchronising the transmitter sending circuit with the receiver circuit, and using very short timescaled pulses, compatible with the very short elapsed period, which is the case for close range measurements. The timescale used in computer operation is micro seconds, (micro 10 6) and this is fully utilised with the present arrangement.

Synchronisation is achieved by using a common clock oscillator, frequency divider, and one shot multi-vibrator to open two electronic And gates, during the same period of time. One gate enables the transmitter to transmit whilst the other enables the receiver circuit to receive, during the common period in which the gates are held open which is one micro second. During each period there are transmitted 10,500 frequency cycles. If the target is 200 ft away then the elapsed period for the pulse to go there and back is slightly less than .39 times one micro second. In other words only 6,441 cycles will be received during the period of one micro second. The period between sample pulses which are fed to the computer may be chosen to give the computer time to do the calculations, and a buffer memory is placed between the frequency counter and the computer memory.It is clear that in the light of the above calculations that a 'shutter speed' of 2 micro seconds or less will be satisfactory in practice, thanks to the exact synchronisation, of the transmitter with the receiver. The shutter speed refers to the period that the gates are open. It is not an object of the present invention to discriminate between opening and closing Doppler frequencies, but to compute the difference between the fixed transmitted frequency, and the critical received frequency, from which the distance to the target is computed. From this information stored in the computer the clearance distance is compared with the recommended clearance, related to the vehicle's velocity, the safe braking distance, and where necessary the rate of clearance erosion. The safe braking distance from the Highway Code is the vehicle velocity in mph times 3 feet.The operation of the dedicated minicomputer and how it may warn the driver will be apparent from the programme logic shown in Fig. 2.

With respect to Fig. 4, the power supply 1, from the 12 volt ignition supplies a bias voltage to a fixed unmodulated frequency oscillator 2, with an electronic AND 12 interposed between the oscillator and the transmitter antenna and dish 3, which transmits a highly directional narrow VHF radio beam. Moreover the RF beam is pulsed such that it transmits for a period of one or 2 micro seconds, and the interval between pulses will be fixed to allow the computer time to operate on its data. Any obstacle 4, whether in motion or stationary, will reflect the transmitted beams back to the receiver dish and antenna aerial 5.The received train of frequency cycles are fed into a high frequency microwave crystal detector 6, and passed through a band-pass filter 7, which rejects all frequencies that are not frequencies reflected from the obstacle which were transmitted by the vehicle's own unique frequency. In this connection the transmitted frequency may be chosen from a narrow band between the range of 8 and 12 Ghz. In this way there is very little possibility that stray radio beams from other vehicles will interfere with the system, should it become universally accepted. The received signal is then passed through a conventional feed-back amplifier 8, to provide a voltage gain of 200, prior to passing through the electronic AND gate 12, on the receiver circuit. It should be noted at this juncture that the gate is synchronised with the gate on the transmitter circuit to open and close in unison.

Meanwhile a fixed-time-interval clock oscillator 9, the output of which is passed through a frequency divider 10, and the lower frequency output is used to synchronise a multi-vibrator 11.

The multivibrator generates precisely spaced rectangular pulses, whose duration is an exact submultiple of the clock oscillator repetition rate. This rectangular pulse is then used to enable the electronic (AND) gates 12, to open in unison for a known time interval (t). During the period of fixed time that the gates are kept open by the rectangular pulse, a series of pulsed frequency cycles are transmitted, and a series of cycles at the analogue frequency are allowed to pass through to an all-in-one Digital Frequency Meter chip in the computer 15. As previously explained when the gates shut in unison, part of the returning pulse of cycles are cut-off representing and equal to the elapsed period for the pulse to reach the target and return. The received number of cycles is then used to compute the distance to the obstacle, which is displayed on the LED read-out 16.Some modern vehicles are fitted with encoded shafts and decoders to give an accurate digital reading of the vehicle velocity. In the absence of such the speedometer 13, must be fitted with an analogue to digital converter 14 which gives a digital output which is fed to the computer, which calculates the safe braking distance, in accordance with the programme stated in Fig. 2. When the rate of closing on the obstacle becomes critical in accordance with the algorithm, it energises the audio oscillator 17, with the appropriate pulse rate, proportional to the rate of closure. The audio oscillator converts the pulses of energy into bleeps of variable pitch which are emitted from the bleeper 18.Parts numbered (6 to 12) inclusive are mounted on a printed circuit board 19, and supplied with a 4 volts regulated DC voltage from the voltage regulator 20, whilst the mini-computer is supplied with a 12 volts regulated voltage from the voltage regulator 21. The dedicated mini-computer 15 will require a regulated 12v supplied via the voltage regulator 21. The computer may be supplied with an input facility (not shown) to discriminate between wet and dry conditions, icy conditions, as well as urban and motorway travel. For urban road use, the addition of a count-down capacitor is necessary to the circuit in order to discriminate, or at least to provide some discrimination between false and valid targets.

The function of the capacitor was described in connection with Fig. 3.

Although the circuitry and function of the many parts shown in Fig. 4, are well known to the art, some individual part circuits are reproduced to give the reader a better understanding of such component parts, and how they function.

Fig. 5, shows a transistorized 1 Mc/s square-wave clock oscillator circuit diagram, with clock output and derived timing wave forms.

Fig. 6, shows the circuit and waveforms of a monostable (one-shot) multivibrator.

For other typical circuits of component parts and diagrams reference may be made to the book publication 'Electronic Computers made simple' by Henry Jacobowitz, as well as various editions of the magazine 'electronics today'.

The accuracy of the distance measuring equipment described depends on the careful correlation of the received train of cycles with distance. The critical frequency is the difference between the fixed RF oscillator 2 on the sending circuit and the apparent frequency on the receiving circuit. The missing cycles are those cut-off when the gate shuts them out due to the time elapsed. Compensation for any instrument error determined from experiment may be automatically corrected by the mini-computer, whose function it is to correlate the measured frequency to distance and actuate the light emitting diode LED 16, showing the actual distance to the obstacle.

It may be cheaper and more practical to replace the frequency meter with a carefully chosen transducer to measure the electro-magnetic energy of the received train of cycles after it has been amplified. The meaning of the functions and how they are derived will now be explained with reference to the simple computer programme stated in Fig. 2 Transmission frequency= 10.5 GHz Transmission period = one micro second Transmitted train of cycles=10,500 per micro second.

Fl =10,500 F2=Received number of cycles in one micro second counted by computer.

Difference between transmitted number of cycles and number received in one micro sec ond=F3 =(F1 -F2) C=constant which relates the speed of light=196,000 miles per sec; to the transmitted number of cycles during the period of one micro second.

196000X5280X 1 C= =0.04928 10,500X 10X2 N.B. the fraction 1/2 relates the time taken to go to the target and return.

D1=Distance to obstacle=F3XC feet D2=Safe braking distance=3XVI feet where Vl=Vehicle velocity.

It should be noted that in the case of 2 micro second pulse periods then the value of the Constant is half that shown above. Moreover upon running the programme it will be found that the upper limit produces a closing speed of 175 mph, for a safe braking distance of 525 ft; when the received frequency F2 is equal to zero. This is a satisfactory system therefore, since the Doppler frequency is insignificant, thanks to the very fast shutter speed. In the actual hard wire programme the statement 'Print D1' will become an instruction to display D1 on the LED for the use and convenience of the driver. The statement 'If F3t0' ensures that should a stray frequency or spurious signal be picked up during the very short micro second then the programme will ignore it, if it is sufficient to cause an impossibility.

Referring to Fig. 2, the following numerals apply: 1. Vehicle in front 2. Vehicle behind.

3. Sending antenna and radar dish 4. Receiving antenna and dish 5. Transponder with variable frequency changer.

For icy conditions the braking distance appearing under label number 70 in the programme will require another step in the programme and advice should be sought from The Ministry of Transport on this subject. Again a different set of braking distances are required for urban motoring, on today's congested roads. In this connection it is proposed to retain one special red bulb on matrix lamps which will be illuminated automatically whenever the wet bulb thermometer reading falls below freezing. It will be actuated by the dedicated mini-computer from an all weather digital thermometer mounted beside the lamp, or could operate as a separate lamp standard on roads other than motorways which may be subject to patches of black ice, and sheet ice.In the latter case gritting and even salting can still leave the surface extremely treacherous, where sheet ice is underlying the salt, or grit or both.

The use of-a transponder opens up a number of possibilities, foremost is the transfer of coded messages such as the rate of closing on the vehicle in front of the vehicle being monitored. This is important information during times of crisis such as a broken down vehicle on a motorway lane, or worse, information such as a motorway multiple collision which closes all lanes, which this invention seeks to prevent. A red light on the fascia could be used to inform the driver of such danger ahead, in addition it might be used to sound a special alarm to inform other drivers of impending danger. Again should be proposed system become mandatory, and should there remain difficulties with false and spurious signals, it could be used to trigger a unique RF signal, triggered by the sending RF signal. Unique in that it will be a signal on a RF which the vehicle is designed to receive.There are many ultra high frequencies UHF from which to choose. In this respect the transponder will need to be fitted with a frequency divider, and respond with the unique frequency sent to it under coded information by the following vehicle.

This feature will require another step in the computer programme to compute the closing speed, which is determined from successive readings of vehicle spacing.

The resolution of digital frequency meters is better than 0.1 Hz per 500 MHz, and are designed using large scale integration LSI techniques on 40-pin custom chips, but to save on cost they may be replaced by transducers which will measure the electro magnetic energy of the received pulse, as mentioned earlier.

It is recognised that on certain occasions automatic braking is desirable and necessary to prevent accidents, or further accidents. For example, in the worst event such as the vehicle driver suffering a black-out, heart attack, or losing control for any other reason, only such a device will prevent an accident, or a carnage which results when a heavy vehicle ploughs into a motorway multiple collision. Unlike known systems which have been designed to provide automatic braking, and are known to initiate braking when false targets penetrate the target discrimination circuit, this system will only initiate braking after 33% safe braking distance has been eroded. In effect the target will have been in sight for a considerable time prior to initiation of auto-braking. Use of the device may be restricted to motorways.

A simple automatic braking system will now be described, which is controlled by the computer programme, but is operant at the discretion of the vehicle driver. The system proposed assumes that the driver is totally incapacitated and like a 'Deadman's handle' used on underground trains, it will act to bring the vehicle to a stop, unless the system circuit is over ridden by the vehicle driver, switching it off from a switch on the fascia. The simple system utilises an electric brake gear motor, an arrangement of pulleys which provide a mechanical advantage, similar to a block and tackle, and a steel wire. One end of the steel wire is fixed to the pulley wheel on the servo motor's spindle, and passed around the other pulley wheels in the system, as well as a hole in the brake lever and a hole in the clutch lever.Springs and guides are so positioned that the brake pedal and clutch pedal may be freely operated in the usual way, since the springs will keep the wire taught at all times. Each pulse of electricity representing a signal from the computer will rotate the electric motor through 360 degrees and will commence depressing the brake pedal, whilst at the same time opening the clutch by similar action. As soon as the signals stop, the servo motor will release the tension on the cable and the spring action of both the clutch pedal and brake pedal will return them to their normal position. The arrangement of the pulleys will be such that the braking action and opening the clutch action, are operated to emulate the human reaction, and will not therefore damage the clutch or brakes.

Although not essential the throttle action may be similarly controlled. As determined by the computer where the speed of closure is critical which occurs when a stationary obstacle is in sight the speed of the electric motor must be synchronised with the closing speed. Most small servo motors are designed to have two speeds, and can easily be adapted for this task.

In the past other automatic braking systems have been proposed, but this system has the advantage that it does not interfere in any way with the manually operated systems universally used whether servo assisted or not, and of course can be over-ridden at the touch of a switch, or button. It is not an object of the present application to provide the design for such an automatic braking system, merely to provide the ideas for a system for foolproof operation.

Claims (6)

1. On a motorway or highway, apparatus including data input, means for measuring visibility, means for receiving such information, computer means connected to said data input means, and operant for using said information to indicate safe speed restriction on motorway matrix lamps, such safe speed being controlled by said computer in which stored lookup tables or mathematical formulae are used to compute safe speeds applicable to the prevailing visibility, operant 24 hours per day, data output means connected to power actuator to switch-on appropriate speed restriction display; means of excluding daylight and headlamp incident light from measurements of visibility, means of preventing motorway carbon particles and other airborne pollution from forming on lenses of instrument; means for providing a vehicle driver with a continuous read-out of the distance to an obstacle or vehicle in front, and an audio warning whenever the safe braking distance is eroded, comprising data input from sonar or radar equipment, velocity input from vehicle tachometer means for receiving such information, computer means connected to said input means and operant for using said information to compute clearance distance to obstacle or vehicle in front, safe braking distance related to vehicle velocity, speed of closure on obstacle in front, data output means comprising: light emitting diode (LED) display of distance to obstacle, variable pitch audio warning bleeper, and automatic braking system, for decelerating or stopping the vehicle, all in accordance with the computer programme.

2. Vehicle spacing equipment according to Claim 1, comprising a synchronised transmitterreceiver, UHF pulsed radar circuit in which the shutter speed of one micro second or more, compatible with the speed of light, shuts out a proportion of the reflected train of cycles in direct proportion to the distance to the obstacle.

3. Vehicle spacing equipment according to Claim 1, or Claim 2, which discriminates between false and valid reflected signals by using highly directional radar transmitter and receiver dishes, very short pulsed UHF unique frequency, in which Doppler frequency is insignificant in which the pulsed period is relatively very short compared with the interval between pulses, and in which the computer programme rejects reflected signals which last longer than the pulse period, with means of curtailing the range of the system to operate within 150 metres.

4. Vehicle spacing equipment according to Claims 1, 2, or 3, which measures the distance to an obstacle by comparing the fixed pulse of UHF cycles or electro-magnetic energy with the received number of cycles, or electro-magnetic energy in unit time, from which it computes the actual distance to the object and compares the distance so obtained with the computed safe braking distance which is related to the vehicle velocity.

5. Vehicle spacing equipment according to any one of Claims 1 to 4, wherein said means includes automatic audio warning, comprising electric signal of such intermittant energization being in direct proportion to the rate of closing on the obstacle that the pitch and volume of a bleeper are varied in accordance with such rate and degree of erosion of safe braking distance, and independent of all other parameters.

6. Vehicle spacing equipment according to any one of Claims 1 to 5, wherein said means includes automatic braking system, for stopping or decelerating the vehicle, to be actuated by signal from computer whenever 33% of the safe braking distance has been eroded, such means controlled by computer, with over-ride switch on fascia, and independent of manually operated conventional system, means to gradually apply brakes, open clutch, close throttle, comprising: brake electric gearmotor, having two rotational speeds, cables, pulleys embodying a mechanical advantage, and guides to auto-operate braking system thereby applying brakes at a rate proportional to rate of closing on obstacle, bringing vehicle to a halt within the eroded braking distance.

6. Vehicle spacing equipment according to any one of Claims 1 to 5, wherein said means includes automatic braking system, for stopping or decelerating the vehicle, to be actuated by signal from computer whenever 33% of the safe braking distance has been eroded, such means controlled by computer, with over ride switch on fascia, and independent of manually operated conventional system, means to gradually open solenoid valve on hydraulic circuit which opens valve to hydraulic reservoir which actuates slave cylinder which compresses hydraulic fluid in manually operated hydraulic braking system thereby applying brakes at a rate proportional to rate of closing on obstacle, bringing vehicle to a halt within the eroded distance.

CLAIMS Amendments to the claims have been filed, and have the following effect: Claims 3 and 6 above have been deleted or textually amended.

New or textually amended claims have been filed as follows:

3. Vehicle spacing equipment according to Claim 1, or Claim 2, which discriminates between false and valid reflected signals by using highly directional radar transmitter and receiver dishes, very short duration pulsed ultra high frequency, in which Doppler frequency is insignificant and the pulsed period is relatively very short compared with the interval between pulses, in which the computer programme rejects reflected signals containing more RF cycles than the limit with means of curtailing the range of the system to operate within 150 metres.