WO1995008454A1

WO1995008454A1 - Apparatus for indicating driving distances

Info

Publication number: WO1995008454A1
Application number: PCT/GB1994/002077
Authority: WO
Inventors: John Stanley Hall
Original assignee: John Stanley Hall
Priority date: 1993-09-24
Filing date: 1994-09-23
Publication date: 1995-03-30
Also published as: AU7663294A; GB9319721D0

Abstract

Apparatus or means, on a first vehicle, providing the driver of a second vehicle, with information characterising the distance between the two vehicles. Information is selectively presented to the second driver via masking means which utilise the angular relationship existing between the eyes of the second driver and the apparatus or means. Masking is accomplished via sets of inclined, parallel, opaque, slats and vertical separators, which create apertures in a masking frame in front of an illuminated green and red coloured, translucent sheet. The masking frame (16), has a grill of vertical separators (20), which divide downward sloping slat members (13), from upward sloping slat members (15). Slat members (13) create green coloured, safe distance indicating apertures (21), and slat members (15) create red coloured, unsafe distance indicating apertures (22), in frame (16), which is placed in front of the sheet (17).

Description

APPARATUS FOR INDICATING DRIVING DISTANCES

This invention relates to apparatus for indicating safe and unsafe driving distances to the driver of a vehicle following another vehicle.

It is well established that many road accidents are the result of failure of drivers to maintain a safe distance behind the vehicle in front and the maintenance of a safe driving distance between vehicles is therefore one of the most effective ways to reduce vehicle accidents.

Various methods have been documented which suggest ways to aid the driver in establishing a safe driving distance behind the vehicle in front but these rely on complicated techniques and many require equipment on the vehicle in front and in the one following. Furthermore, in those instances where only the following vehicle contains the operative apparatus, the driver of the vehicle in front (the first driver) has to depend on the presence of the apparatus in this following vehicle and that it is utilised!

Thus, for instance, it is known, from British Patent Specification 2 260 437 A, that apparatus exists for indicating to the driver of a following vehicle that the vehicle separation is inside, or outside, of safe limits, but such apparatus has to be fitted on both vehicles.

It is an object of the present invention to at least reduce problems met with the known apparatus.

According to the present invention, apparatus is provided on a first vehicle for indicating safe and unsafe driving distances to the driver of a second vehicle which is following the first vehicle. This is implemented by constructing the apparatus so that visual information indicating safe and unsafe driving distances, respectively, is alternately masked from view as the second vehicle approaches the first. The information presented can be in the form of coloured bands or a warning notice, etc.

Thus, in contrast with what is already known, the present invention provides the first driver with apparatus to be fitted to the first vehicle which does not require additional apparatus on the following vehicle for the invention to function and which therefore provides the first driver with independent means of protection against rear-end collisions.

In one form of the apparatus, selective masking of the visual information is achieved by utilising parallel sets of opaque slats in front of it. For the safe distance, one set of parallel slats is inclined at one calculated angle with respect to the horizontal and for the unsafe distance, another set of parallel slats is inclined at another angle with respect to the horizontal. Horizontal is taken to mean the ground plane on which the wheels of the two vehicles lie.

The angles of inclination of the sets of slats depend on i) the selected safe and unsafe driving distances, ii) the chosen dimensions of the apparatus, iii) the height above the road surface at which the apparatus is mounted on the first vehicle and iv) the height of the eyes of the second driver above or below the level of the apparatus. Analysis of the range of vehicles on which the apparatus is to be mounted will reveal where it is most suitably mounted and this will dictate the design. It is possible that a range of designs will be necessary to cater for various designs of vehicle and it is anticipated that particular designs will be necessary for cars and others for lorries, buses, coaches, etc. However, it is possible that a general design will emerge for application to a wider range of vehicles.

The actual design of the apparatus will also depend on the method of use. Thus it can be in the form of an individual rear light or lights, which is/are mounted inside or outside of the vehicle, towards the rear, or it can be in the form of modified rear light assemblies. Alternatively, it can be in the form of a self contained warning sign which contains fluorescent material and/or reflectors and/or its own source of lighting. The basic principles of the invention can also be applied, in appropriately designed and sized apparatus, anywhere else on a vehicle where it will perform its intended function.

In order to explain, in more detail, the operation of the invention, reference will now be made to the accompanying drawings, in which:

Figure 1 represents, in schematic form, a side elevation of the road situation as a second vehicle approaches a first, thereby demonstrating the function of the invention.

Figure 2 represents, in schematic form, part of one embodiment of the invention for indicating safe driving distances.

Figure 3 represents, in schematic form, part of another embodiment of the invention for indicating unsafe driving distances.

Figure 4 represents, in three dimensional exploded form, one version of the apparatus for indicating safe and unsafe driving distances. Figure 5 shows, in schematic side elevation, the significance of the mounting position for the apparatus and of other parameters, as the second vehicle approaches the first.

Figure 6A shows, in side elevation, a geometric representation of a section of the apparatus shown in Figures 2 to 4.

Figure 6B shows, in side elevation, a geometric representation of another section of the apparatus shown in Figures 2 to 4.

Figure 7 shows, in schematic form, how an embodiment of the invention can be implemented via cylindrical holes formed in a block.

With reference to Figure 1, which represents a side elevation, the rear part of a first vehicle, 1, is shown in relation to three positions, 2A, 2B and 2C, of a second vehicle, 2, with both vehicles resting on the horizontal road surface, 3. HL1 , is a horizontal reference line.

Safe, and unsafe, distance indicating apparatus, 4, has directional viewing extremities indicated by straight lines 5, 6, 7, and 8, where lines 5 and 6, represent the viewing boundaries created by the masking slats for safe distance driving and where straight lines 7 and 8 represent the viewing boundaries created by the masking slats for unsafe distance driving. Lines 5 and 6 could thus correspond with the provision of a green visual indication means in the apparatus and lines 7 and 8 could correspond with the provision of a red visual indication means in the apparatus.

For position, 2A, of the second vehicle, the eyes of the driver of the second vehicle, 2, can be seen, in position 9A, to lie within the green viewing boundaries (lines 5 and 6) i.e. within the "green viewing region", 10.

For position 2B of the second vehicle, the eyes of the second driver can be seen, in position 9B, to lie within both the green and the red viewing boundaries (lines 7 and 6) i.e. within the "green and red viewing region", 11.

For position, 2C, of the second vehicle, the eyes of the second driver can be seen, in position 9C, to lie within the red viewing boundaries (lines 7 and 8) so that now, only the red area of the apparatus can be seen from within the "red viewing region", 12.

It can therefore be readily seen how the second driver moves from the "green viewing region" through the "green and red viewing region" and into the "red viewing region", as the second vehicle approaches the first.

It is to be noted that the design of the arrangement of the slats could be such that the green and red visual indication region, 11, does not exist, i.e. there can, if desired, be a sharp boundary between the observation of the green region, and of the red region, by the second driver.

With reference to Figure 2, which represents a side elevation, that part of the apparatus, 4, (Figure 1) which provides the safe distance indication to the second driver, is shown.

Parallel slat members, 13, which are part of a main frame, 16, of slats and vertical separators, (see later) extend from an illuminated green translucent section, 23, in a downward direction. For one pair of adjacent slats, two lines, 5 and 6, are shown extending from the vertical extremities of the front part of section 23, thus showing how the region, 10, within which only green light is visible to the second driver, is defined. Each pair of adjacent slats creates a safe distance indicating aperture, 21, for viewing the green visual indicator means, 23. The light source can be any suitable source of white light.

The apparatus functions by defining viewing boundaries which extend from point, 14G, where the lower boundary line 5LR and the upper boundary line, 6UR, intersect. Line 5LR is parallel with line 5 and line 6UR is parallel with line 6, and the horizontal line, HL2, is used to enable translation of the understanding of the function of the apparatus shown in Figure 2, to Figure 1, where horizontal ground line, 3, is parallel with horizontal line, HL2.

With reference to Figure 3, which represents a side elevation, that part of the apparatus, 4, (Figure 1) which provides the unsafe distance indication to the second driver, is shown.

Parallel slat members, 15, which are part of a main f ame, 16, of slats and vertical separators, extend from an illuminated red translucent section, 24, in an upward direction. For one pair of adjacent slats, two lines, 7 and 8, are shown extending from the vertical extremities of the front part of section 24, thus showing how the region, 12, within which only red light is visible to the second driver, is defined. Each pair of adjacent slats creates an unsafe distance indicting aperture, 22, for viewing the red visual indicator means, 24.

Once again, the apparatus functions by defining viewing boundaries which extend from a point, 14R, where the lower boundary line 7LR and the upper boundary line, 8UR, intersect. Line 7LR is parallel with line 7 and line 8UR is parallel with line 8, and the horizontal line, HL3, is used to enable translation of the understanding of the function of the apparatus shown in Figure 3, to Figure 1, where horizontal ground line, 3, is parallel with horizontal line, HL3.

With reference to Figure 4, one version of the apparatus, parts of which have already been shown in side elevation in Figures 2 and 3, and referred to with reference to Figure 1 , is shown in exploded form.

The apparatus, 4, comprises a masking frame, 16, which masks elements of an illuminated, coloured translucent sheet, 17. A transparent front face 18, and a concave rear portion, 19, are fixed together so as to contain elements 16 and 17. The masking frame, 16, has a grill of vertical separators, 20, each of which divides downward sloping slat members, 13, from upward sloping slat members, 15. The downward sloping slat members, 13, create safe distance indicating apertures, 21, and the upward sloping slat members, 15, create unsafe distance indicating apertures, 22, in the masking frame, 16. The translucent sheet, 17, has alternate green, 23, and red, 24, sections, such that the green sections, 23, lie immediately behind the safe distance indicating apertures, 21, and the red sections, 24, lie immediately behind the unsafe distance indicating apertures, 22.

There thus exists a plurality of safe, and unsafe, distance indicating apertures 21 and 22, respectively, linked, via masking slats, 13 and 15, respectively, with a plurality of coloured visual indicator means, 23 and 24, respectively.

In order to prevent unwanted reflections from interfering with the operation of the apparatus, the slats, 13 and 15, and the vertical separators 20, would, ideally, be coated with black non-reflective paint or otherwise treated so as to be non-reflective or manufactured from non-reflective plastic or other material.

Various methods are available for fixing the components of the apparatus together and one method could utilise screws which pass through holes formed in the centres of the edges of, and in the corners of, the front face, 18, the masking frame, 16 and the translucent sheet, 17, to engage in threaded holes in the centre of the edges of, and in the corners of, the concave rear portion, 19.

Alternatively the four units could be designed so as to "snap" together by use of suitably designed friction devices or they could be held together by means of adhesive or welded together by use of ultra sonic techniques. Yet another alternative would be to design the various elements, 16, 17, 18 and 19, so that the front face, 18, fits into a frame (not shown) and so that the masking frame, 16, and then the translucent sheet, 17, fit into this frame behind the front face, 18. The rear portion, 19, containing the lighting unit (not shown) would then close over the rear of the frame and be fixed in place by twistable catches etc., so that the whole unit resembles a picture frame assembly, in the way that its separate components are held together. Rubber seals could be used to provide resistance from mechanical shock and waterproofing.

For the purposes of maintaining simplicity in the diagrams, those parts of elements 16, 17, 18 and 19, which provide such mounting facilities, are not shown.

As an alternative to the arrangement of slats and vertical separators shown in Figure 4, the pairs of adjacent members of one set of parallel slats of type 13, inclined at one angle with respect to the horizontal, could have pairs of adjacent members of the set of the other type, 15, inclined at another angle with respect to the horizontal, placed immediately above them, thus creating a vertically alternating pattern of distance indicating apertures like 21 and 22.

As a further alternative to the arrangement of slats 13 and 15, shown in Figure 4, it is pointed out that the there could be just one set of slats like slats, 13, inclined at the same angle as the slats 13, immediately to the side of just one set of slats, like slats, 15, inclined at the same angle as the slats, 15. This would require a less complicated arrangement of slats and vertical separators than the one shown in Figure 4, and would have a laterally changing appearance when the second driver passed from the unsafe viewing distance to the safe one. Such an arrangement would, however, be less compact and would not allow the flexibility in displayed pattern that could be obtained with the design shown in Figure 4.

Yet another alternative would be to have the two sets of slats of type 13 and 15, above one another. This would have a vertically changing appearance and, as for the side by side arrangement, would be less complicated but less compact and offer le ,s flexibility in display pattern.

With reference to Figure 5, which represents a schematic side elevation, the two positions, 9A and 9C, of the eyes of the driver of the second vehicle, 2, are shown in relation to the position of the apparatus, 4, mounted at the rear of the first vehicle, 1. The horizontal distance of the eyes from the imaginary point of intersection 14G or 14R, of the boundary lines for viewing the green or red translucent sections, respectively, is Dl , for position, 9A, and D2, for position, 9C, of the eyes. It is to be noted that, for convenience in the diagram, points 14G and 14R are shown coincident with one another, whereas, from

Figures 2 and 3, 14G can be seen to be above point 14R.

However, this does not affect the values of Dl and D2, since points 14G and 14R lie on the same vertical line.

The height of the apparatus is HI and the vertical height of the centre of the apparatus, 4, above the horizontal ground level, 3, is D3. The vertical height of the eyes of the second driver above the centre of the apparatus, 4, is D4. Once again, although points 14G and 14R are at different vertical distances below the level of points 9A and 9C, the appropriate value of the dimension D4 will be used with the dimension Dl or D2, for the determination of the safe and unsafe distances respectively, corresponding to the observation of the green and the red, visual indication means, respectively.

Equations, to be derived later, will show how the safe and unsafe distances, respectively, between the first and second vehicles, can be determined using distances measured from points 14G and 14R, respectively, but it is the distances from the rear of the apparatus, 4, which are actually required. However, the error encountered will be extremely small in comparison with the separation distances involved and, anyway, the error can be calculated and hence eliminated, if desired.

With reference to Figure 6A, which represents a side elevation, there is shown a geometric representation of a section of the apparatus, 4, shown in Figures 2 to 4.

Two parallel slats, AB and DC represent two of the slats, 15, shown in Figure 3. Slat AB is inclined at an angle BAF with the horizontal whilst slat DC is inclined at an angle EDC with the horizontal. Line DGBH represents the upper limit for viewing a ray of light from the rear part, represented in profile by line AD, of the apparatus, 4, and line AGCI represents the lower limit for viewing a ray of light from the same rear part.

The lines thus intersect at point, G, at an angle of BGC, which represents the angular range provided for viewing the rear part, AD, of the device.

Figure 6B represents the mirror image of Figure 6A reflected in line JK as mirror (where line JK is parallel with line AF) with line LM representing the corresponding mirror for reflecting Figure 6B back to Figure 6A. The extension of line JK coincides with line LM.

TRIGONOMETRY

Trigonometry can now be used to derive relationships between the angle of inclination of the slats and the angle within which the rear part of the device can be viewed.

It should be noted that, although the complete viewing ranges defined by lines 5LR to 6UR (Figure 2) and lines 7LR to 8UR (Figure 3) are actually required, the geometric rule of similar triangles shows that point G could be used instead of 14R or 14G, together with the appropriate value of the horizontal distance of the eyes of the second driver from point G.

Assuming the following dimensions for the components of the apparatus:

Vertical separation of Slats = AD = BC = V

Horizontal separation of Slats HS = AF = see later

Length of slats = LS = AB = DC Height of driver's eyes above the optical centre line through points 14G or 14R, of the apparatus = D4

Horizontal distance of driver's eyes from the optical centre, 14G or 14R, of the apparatus = d

Horizontal distance of driver's eyes from point 14G or 14R, for position 9A of driver = Dl (Figure 5)

Horizontal distance of driver's eyes from point 14G or 14R for position 9C of driver = D2 (Figure 5)

Since HS is a dependent variable (being dependent on LS and the slat inclination) it has to be represented in terms of LS and the slat inclination.

Thus:

SIN(EDC) = CE/DC = (BE-BC)/DC = [DE*TAN(EDB)-V]/DC (1)

SIN(BAF) = BF/AB = (BC-FC)/AB = [V-AF*TAN(CAF) ]/AB (2)

Since DC = AB = LS

and HS = DE = AF = LS*C0S(CDE) = LS*COS(BAF)

Rearranging equations 1 and 2:

TAN(EDB) = [LS*SIN(EDC)+V]/LS*COS(CDE) (3)

TAN(CAF) = [V-LS*SIN(BAF)]/LS*COS(BAF) (4)

Since angle EDB = angle BGK and since angle CAF = angle CGK, the horizontal distance, d, in feet, of the eyes of the driver from the device centre point, G, when, theoretically, the rear part, AD, of the device is in view, can be represented by the expressions:

d = D4/[TAN(EDB)] (Figure 6A) (5)

d = D4/[TAN(MGI)] (Figure 6B) (6)

(For definition of D4 see Figure 5)

From Figure 6A, AD is only visible to the driver from a distance of infinity down to that which allows TAN(EDB) to equal D4/d.

From Figure 6B, AD is only visible to the driver from a distance of infinity down to that which allows TAN(MGI) to equal D4/d.

It can therefore be seen how the above reasoning and equations can be used with particular values for the safe and unsafe distance, to arrive at dimensions and angles of inclination for the components of the apparatus, 4.

It is appreciated that the use of green lights or reflectors may cause confusion and may therefore never pass current legislation in certain countries. Vehicle Regulations aim to avoid confusion during driving, by preventing unauthorised changes to the appearance of vehicles. If legislation will not permit the use of green or other colours of visual indicator means, then the green visual indicator means could be replaced by further red visual indicator means so that translucent sheet, 17, is completely red in colour, with slats, 13, and 15, angled so as to provide an enhanced red light as the second vehicle gets closer to the first, than the legal distance.

It is correct to say, however, that in this case, the apparatus would function with only the slats, 15, present. Provided that the regulations regarding the intensity, size and position of, rear lights, is satisfied, the provision of an enhanced red light as a vehicle gets closer to the one in front, will produce an effect similar to that obtained when the vehicle brake lights are applied. The observed change will be more abrupt, the greater the relative speed of the two vehicles, and so will also provide a warning to the second driver that the second vehicle is approaching too rapidly. Moreover, if the rear lighting configuration meets with current legislation, additional lighting which introduces vertical or diagonal stripes, or other patterns, to be seen by the second driver, should be acceptable.

As already stated, point 14R is below point 14G, and the difference in height is roughly equal to the vertical length of the apparatus. Point 14R could be made to coincide with point 14G, by having the set of upward sloping slats, 15, directly above the set of downward sloping slats, 13. Alternatively, points 14R and 14G, could be made to coincide, by appropriate adjustment of the length, separation, and angles of inclination, of these slats. The actual separation of slats, 13 and 15, will depend on the findings of further experimentation and it is pointed out that the configurations shown in this description are not intended to be limiting.

Due to the symmetry of the geometric arrangement of the slats, if the apparatus, 4, is inverted and mounted above the level of the eyes of the second driver, the dimension D4 (Figure 5) becomes the vertical distance of the level of the eyes of the second driver below the optical centre, 14G or 14R of the apparatus, 4.

However, the equations derived with reference to Figures 6A and 6B, will continue to apply. It is appreciated that when the second vehicle is a lorry or other vehicle in which the second driver is higher and for which the dimension, D4, is greater, this will allow the red visual indicator means, 24, to be seen at a greater distance from the first vehicle. A compromise is therefore necessary.

It is interesting to observe that lorries, being heavier and bulkier, might benefit from being spaced at greater distances than are cars.

With reference to Figure 7, a block, 25, of wood, metal, plastic, or other suitable material, has, formed within it, a cylindrical hole, represented in cross section by points A,B,C and D, at an angle with respect to the horizontal. By analogy with the explanation given with respect to Figure 6A, the rear part, AD, of the hole, has light entering from a direction shown by the arrows. The rear part, AD, can thus be seen from the other end of the hole, only from directions within the boundary represented by lines AGCN and DGBH, where AGCN represents the lower boundary line for viewing AD and where DGBH represents the corresponding upper boundary line. Point G represents the point of intersection of the two lines.

Thus, by forming a number of cylindrical holes, all at the same angle of inclination, in the block, 25, in the shape of a cross on the face, 26, of the block, the cross pattern will only be visible for a range of distances of the observer from the block. For convenience in the diagrams, the face of block, 25 is drawn smaller than it should be. Also, the holes could be rectangular or of any other shape.

By forming another set of holes in the block, at an alternative angle of inclination and in an alternative pattern, say that of a horizontal line, this pattern will only be visible for another range of distances of the observer from the block, 25.

By making the holes, particularly non circular ones, large enough, and by arranging them so as to create letters, warning notices can be created, thereby implementing the principles of the invention through use of words.

It is pointed out, with reference to the apparatus, 4, described in the foregoing, that the slat members 13 and 15, will be separated at fixed distances and set at particular angles. However, the apparatus could be designed so that the slats are adjustable, either in length, separation, vertical position or angle of inclination, or in any combination of these. Furthermore, such adjustment could be designed to take place during factory assembly, home assembly or as supplied to the end user. It is, however, appreciated that legislation may limit the flexibility in design for end use, in order to prevent incorrect use.

The apparatus described has involved green and red coloured visual indicators but other, different, contrasting colours could be used. The visual indicator means implemented via the green and red coloured sections, 23 and 24, are in the form of a series of vertical stripes but these could be slanting and shapes other than stripes could be used, e.g. crosses. It is also pointed out that more than two visual indicator means could be used in the apparatus. This would allow any design of pattern, even words, to be created.

Thus, each visual indicator means, 23 or 24, could be of different composition along its vertical length. If, for example, the red visual indicator means, 24, comprised alternate red and clear translucent sections along its length, it would appear as a series of horizontal bands, consisting of red and white mixed together, which become progressively more intense as the second vehicle gets closer to the first. As each clear section comes into view, a pulse of white light will be added to the whole, and as each red section comes into view a pulse of red light will be added to the whole. This in itself should draw the attention of the second driver to the unsafe distance situation and more noticeable effects will be possible by appropriate design of the apparatus and appropriate choice of shape and colour of the visual indication means.

It has been stated that any suitable source of white light could be used in the apparatus but it is pointed out that if the translucent sections 23 and 24, are not coloured, colours can be created by utilising light bulbs of different colours, light emitting diodes, or neon, or other gas discharge, tubes. Fluorescent reflective strips could also be used, either alone or in conjunction with a light source.

In order to ensure that the apparatus is in use whenever the vehicle provided with it, is in use, it is suggested that means for switching it on whenever the car is in use, be implemented. Where the apparatus forms an integral part of new vehicles, it will normally be connected to the vehicle's electrical system and could be linked with the usual ignition controlled switching equipment.

As an alternative to being supplied as an integral device in new vehicles, the apparatus could be supplied as an accessory to be provided with power by the vehicle or to be supplied with its own power. The former case lends itself to easier implementation of automatic switching but the latter case makes fitting and implementation easier. It is also recommended that a solar powered electrical supply could be utilised with the apparatus and that this could also be arranged to be powered by the energy derived from ambient light or the lights of following vehicles.

So that the intensity of the light in the apparatus can be maintained under changing ambient light conditions, it is recommended that means be provided for implementing this. This could be important because the light would need to shine more brightly on a sunny day than on a dull day and, furthermore, at night, the intensity might need to be reduced because the vehicle's exterior lights would be switched on and, anyway, the contrast between the general background and the apparatus would be greater at night. Such light intensity control could be implemented via sensors and circuitry which sense, and provide feedback control for, changes in ambient light intensity.

Where the apparatus is to be used outside the vehicle, it will be important for it to be constructed so as to be fully weatherproof and so that, ideally, it functions under poor weather conditions.

The apparatus may be mounted at any suitable and appropriate position on the first vehicle and suggested positions are: the rear bumper, the boot or the roof. It is also possible for the apparatus to be mounted inside the first vehicle on the rear window or on the rear parcel shelf, with appropriate consideration being given to maintaining visibility via the rear window and to maintaining safety by ensuring that if the vehicle stops suddenly, the apparatus and any auxiliary equipment, are not thrown forward onto the driver or passengers. In all cases such mounting means may be fixed or adjustable. The provision of means of adjustment of the angle of inclination of the whole unit will be important for calibration and final setting up of the apparatus.

It is also pointed out that the concave rear portion, 19, of the apparatus, 4 (Figure 4) could be of a different shape from that shown and that the whole assembly could be designed so that the masking frame, 16, and the translucent section, 17, can be easily changed e.g. by sliding them into place. This will allow the same basic design to be used to create apparatus for indicating different safe and unsafe driving distances corresponding to different driving speeds.

Alternatively, or additionally, the design of the apparatus having adjustable slats will be useful here. It is anticipated that four main speeds will need to be catered for, corresponding to four types of road situation. These are: built up areas, where the speed limit is 30 m.p.h., dual carriageways, where the speed limit is 40 or 50 m.p.h, and motorways, where the speed limit is 70 m.p.h.

It is appreciated that such differing speeds will require differing angles of inclination for the slats and that this will require a more complicated design for a version of the apparatus, 4, which will cater for more than one speed of the protected vehicle in the one unit. The important factor is the ability to link the speed of the first vehicle, and hence the speed of the vehicle immediately following it, with the visual indicator means to be presented to the second driver.

One suggested method would involve incorporation of electromagnetically operated slats which have their angles of inclination altered via power from the electrical supply of the first vehicle and where the angle of inclination is adjusted by microprocessor or logic controlled circuitry which is programmed to respond to the varying speed of the first vehicle through an electronic link with its speedometer or with on board, speed sensing equipment.

It is also possible for a number of different vehicle speeds to be catered for in the one unit by arranging for the angle of inclination of the whole unit to be altered through a link with speed sensing equipment. In a simplified version of such alternative apparatus, sets of additional slats inclined at particular angles for the relevant speeds, could have their corresponding apertures (similar to apertures 21 and 22, shown in Figure 4) selectively masked, electromagnetically, under the control of logic or microprocessor circuitry linked to the speedometer of the first vehicle or other speed sensing circuitry.

Another aspect of safe distance driving concerns protection of the driver of the first vehicle when decelerating to an eventual stop and when the first vehicle is stationary. Here, the necessary minimum distance of the second vehicle behind the first, reduces from a recommended 75 feet at 30 m.p.h, through 40 feet at 20 m.p.h., down to a safe distance corresponding to both vehicles being stationary, e.g., at traffic lights. The second vehicle should then be at a distance behind the first vehicle such that adequate visibility of other vehicles or pedestrians etc., is maintained for the second driver, and such that there is sufficient room for the second vehicle to stop without collision, should the need arise, when both vehicles move off again. Particular designs of the apparatus, 4, could cater for just these situations.

Claims

1. Apparatus or means on a first vehicle, adapted to provide the driver of a second vehicle, with information characteristic of the distance between the two vehicles.

2. Apparatus or means as defined in claim 1, wherein the apparatus or means is placed at the rear of the first vehicle.

3. Apparatus or means, as claimed in claim 1 or 2, wherein the separation between the first and second vehicles, defines an angular relationship characteristic of the distance between the apparatus and the eyes of the driver of the second vehicle.

4. Apparatus or means, as claimed in claim 3, wherein a change in the angular relationship serves to change the nature of the information determinable by the driver of the second vehicle which is displayed on the first vehicle.

5. Apparatus or means, as claimed in claim 4, wherein the information determinable by the driver of the second vehicle indicates safe, or unsafe, driving distances of the second vehicle from the first.

6. Apparatus or means, as claimed in claim, 4 or 5, wherein the change in the visual appearance of the information determinable by the driver of the second vehicle, is arranged to be due to the action of selective masking means incorporated in the apparatus or means, on the first vehicle.

7. Apparatus or means, as claimed in claim 6, wherein the selective masking means is arranged to be implemented via cylindrical holes or other shapes of parallel sided holes, formed at an angle with the horizontal, within a block of suitable material, which is arranged to lie in front of the information determinable by the second driver.

8. Apparatus or means, as claimed in claim 6, wherein the selective masking means is arranged to be implemented via a masking frame consisting of a plurality of opaque slats and vertical separators, placed in front of the information determinable by the second driver.

9. Apparatus or means, as claimed in claim 8, wherein the information determinable by the second driver utilises an illuminated translucent sheet.

10. Apparatus or means, as claimed in claim 8 or 9, wherein the plurality of opaque slats, together with the vertical separators, is arranged to create a plurality of distance indicating apertures, in the masking frame.

11. Apparatus or means, as claimed in claim 10, wherein there is at least one set of parallel opaque slats, fixed so that the planes of the slats are arranged to lie at a predetermined angle with respect to the horizontal, and wherein, together with the vertical separators, there is created a plurality of distance indicating apertures.

12. Apparatus or means, as claimed in claim 10, wherein there are two different sets of parallel opaque slats, and wherein the planes of the slats are arranged to lie at two different angles with respect to the horizontal, so that, together with the vertical separators, there is created a plurality of distance indicating apertures.

13. Apparatus or means, as claimed in claim 12, wherein the set of parallel opaque slats of one type, is immediately to the side of the set of the other type.

14. Apparatus or means, as claimed in claim 12, wherein the set of parallel opaque slats of one type is immediately above the set of the other type.

15. Apparatus or means, as claimed in claim 12, wherein pairs of adjacent members of one set of parallel slats of one type, inclined at one angle with respect to the horizontal, have pairs of adjacent members of slats of the other type, inclined at the other angle with respect to the horizontal, immediately to one side of them, thus producing a laterally alternating pattern of distance indicating apertures, within the apparatus or means.

16. Apparatus or means as claimed in claim 12, wherein pairs of adjacent members of one set of parallel slats of one type, inclined at one angle with respect to the horizontal, have pairs of adjacent members of the set of the other type, inclined at the other angle with respect to the horizontal, immediately above them, thus creating a vertically alternating pattern of distance indicating apertures, within the apparatus or means.

17. Apparatus or means, as claimed in claim 11, wherein the set of parallel slats, is set at a particular angle with respect to the horizontal so that the distance indicating apertures allow the information determinable by the second driver to be seen by the driver of the second vehicle only when it is within one defined range of distances from the first vehicle.

18. Apparatus or means, as claimed in claim 17, wherein the sets of parallel slats are arranged to create distance indicating apertures which allow the information determinable by the second driver to be seen from a defined safe range of distances from the first vehicle.

19. Apparatus or means, as claimed in claim 17, wherein the sets of parallel slats are arranged to create distance indicating apertures which allow the information determinable by the second driver to be seen from a defined unsafe range of distances from the first vehicle.

20. Apparatus or means, as claimed in claims, 13, 14, 15 or 16, wherein the information determinable by the second driver can be seen by the driver of the second vehicle, only when the second vehicle is within each of either of two ranges of distances from the first vehicle.

21. Apparatus or means, as claimed in claim, 20, wherein one of the ranges of distances of the second vehicle from the first vehicle is defined as a safe range.

22. Apparatus or means, as claimed in claim, 20, wherein one of the ranges of distances of the second vehicle from the first vehicle is defined as an unsafe range.

23. Apparatus or means as claimed in any one of claims 4 to 22, wherein the information determinable by the second driver is of any suitable colour.

24. Apparatus or means, as claimed in claim 23, wherein the information determinable by the second driver, seen via the distance indicating apertures, is green in colour.

25. Apparatus or means, as claimed in claim 23, wherein the information determinable by the second driver, seen via the distance indicating apertures, is red in colour.

26. Apparatus or means, as claimed in any one of claims 4 to 25, wherein the information determinable by the second driver, is in the form of a distinctive monochromatic pattern.

27. Apparatus or means, as claimed in any one of claims 4 to 22, wherein the information determinable by the second driver, is in the form of a distinctive multi coloured pattern.

28. Apparatus or means, as claimed in any one of claims, 1 to 27, wherein the apparatus comprises at least one individual rear light.

29. Apparatus or means, as claimed in any one of claims 1 to 27, wherein the apparatus comprises at least one modified rear light.

30. Apparatus or means, as claimed in any one of claims 1 to 29, wherein the apparatus is in the form of a warning sign containing words.

31. Apparatus as claimed in any one of claims 4 to 7 and 8 to 30, wherein the setting of the angle of inclination of functional component parts of the masking frame is controlled electromagnetically in order to set the angles.

32. Apparatus as claimed in claim 7 or 31, wherein the angle of inclination of the whole apparatus can be adjusted to allow for calibration and final setting up.

33. Apparatus or means as claimed in claim 32, wherein the angles of inclination can be linked with the speed of the first vehicle.

34. Apparatus or means, as claimed in any one of claims 1 to 33, wherein the effects of variation in ambient light intensity on the operation of the apparatus on the first vehicle can be compensated for.

35. Apparatus or means, as claimed in claim 34, wherein changes in ambient light intensity are compensated for by use of feedback circuitry which senses changes in the ambient light intensity.

36. Apparatus as claimed in any one of claims 1 to 35, wherein the apparatus is automatically put into use when the vehicle containing it is in use.