The invention relates to a method for the at least partial modification of information on a road sign board, according to the preamble to claim 1.

A road sign board is a board fixed above the road to provide a road user with information. This information normally relates to the directions and destinations which can be reached via the road concerned. Modification of the information is required if the information on the road sign board is not applicable or is not entirely applicable during the temporary period. This may be the case if one or more lanes of the road cannot be used, for example as a result of roadworks. The road includes lanes, possible emergency lanes, exits and verges.

A method of this type is known from practice. In the known method, the information on the road sign board is modified by placing a cover strip with the aid of adhesive or magnetic material at least partially over the information. As a result, it is clear to the road user that the covered-up information is temporarily not applicable.

A disadvantage of the known method is that it is necessary to close the road to all traffic in order to place the cover strip safely on the road sign board. Only after the road concerned has been closed can someone be brought with, for example, a hydraulic platform to the road sign board in order to cover up the latter. Thereafter, the road is fully or partially re-opened to traffic and, for example, work can be carried out. This procedure must be repeated when the temporary condition is ended, for example because the roadworks are completed. Both the fitting and the removal of the known cover strips may in practice take one hour. These two hours in total are taken off the time available for the actual work. This lost time represents a great economic value. The document GB2333658 is an example of an information display apparatus. The invention is intended to eliminate this disadvantage at least partially, or at any rate provide an alternative. In particular, the invention is intended to provide a method wherein a symbol can be fitted temporarily to a road sign board more quickly than in the state of the art.

The invention achieves the object by means of a method according to claim 1. A method for the at least partial modification of information on a road sign board, said road sign board being substantially located above a road during a usage period, wherein the information is visible to road users during the usage period and relates to directions and destinations which can be reached via the road concerned, comprises the following steps:

• disposing at least one symbol on the road sign board, said at least one symbol modifying the information on the road sign board,
• displaying the at least one symbol during a temporary period, said temporary period being shorter than the usage period,
• providing a projector comprising a laser,
• positioning the projector on a position along the road, and
• projecting with the laser of the projector positioned along the road, the at least one symbol on the road sign board above the road.

By projecting the at least one symbol with a projector, it is no longer necessary to physically modify the road sign board, as this can be done from a distance. The preparatory actions, such as the provision of the projector, can take place without, or at least with less, obstruction to the road traffic. As a result, more time is available for, for example, roadworks.

In particular, the at least one symbol is a symbol from the following list: a bar, a cross, an arrow, an alphanumeric symbol.

The laser enables the projection of a bright and sharply defined symbol over relatively long distances.

The projector is positioned along the road. Positions along the road comprise an emergency lane, a road partition such as crash barrier, and a roadside verge. Along the road, the projector may assume a favourable angle in relation to the road sign board without obstructing the traffic on the road and without space next to the road having to be used.

In one embodiment, the projector is positioned at a height of at least three metres above the road. The projection can thus be carried out over the road traffic.

In one advantageous form, the projector is positioned at a distance of at least 150 metres, preferably substantially at 300 metres, from the road sign board. Thanks to this distance, the angles at which a possible plurality of symbols are projected above a plurality of lanes are comparable with one another in such a way that the amount of reflected laser light does not differ significantly for an observer on the road.

In particular, the method further comprises:

• the assessment of a position of the at least one symbol;
• the determination of a difference between the assessed position and a required position; and
• if the difference is greater than a predefined value, the adjustment of the projection in such a way that the difference becomes smaller. As a result, it is possible to compensate for one-off and/or periodic displacements of the projector. A one-off displacement may, for example, occur if a relatively large vehicle drives along right next to the projector, or if the projector is physically struck. Periodic displacements may be caused by vibrations in the set up of the projector.

The invention can use software for controlling a projector for the at least partial modification of information on a road sign board.

The software might comprise instructions for carrying out one or more of the method steps defined above and in the claims.

The invention also relates to an assembly of a road sign board and a device for the at least partial modification of information on the road sign board, according to claim 7.

In particular, the projector is height-adjustable. Thus, the projector can be mounted in a low position before or after the device is located in the required position along the road, and can then be moved to a required height.

In one embodiment, the device further comprises an information board. In practice, an information board primarily needs to be positioned at some distance in front of the road sign board which is modified. By combining the projector and the information board, the positioning of one device is sufficient. Information board is understood here to mean both a board which is provided with symbols attached or presented thereon, and an electronic board that displays symbols by means of, for example, LEDs, or LCDs.

In one particular form, the projector is attached to the information board and the information board is movably connected to the device in order to be moved from a low transport position to a high usage position. This is a particularly advantageous and technically surprisingly simple solution, wherein hardly any additional measures are required on an existing message sign trailer in order to move the projector to the required height.

In one embodiment, the location means comprise wheels for moving the device over the road. This enables simple and fast positioning of the device with the projector.

In one particular form, the device further comprises an electronic camera. This offers the facility to control the laser manually and remotely.

In one embodiment, the device further comprises a control unit to control the projector.

In particular, the electronic camera is actively connected to the control unit and the control unit is designed to control the projector on the basis of an observation of the electronic camera. This enables the projector to be controlled automatically.

In one embodiment, the at least one symbol extends at least partially over the information. In this way, it is made clear to the road user that the information concerned is currently not applicable.

In particular, the method further comprises the removal of the at least one symbol from the road sign board. As the at least one symbol has been projected, it can be removed much more quickly than the known symbols which are affixed to road sign boards.

In an alternative embodiment, the projector comprises a lamp. A projector of this type further comprises, for example, a cathode-ray tube, LCDs, or a Digital Micromirror Device and is also referred to as a beamer. A particular form is a beamer with a plurality of LEDs as lamps.

The location means preferably comprise stabilization feet. These ensure additional stability of the device if the device has been positioned along a road to project the at least one symbol.

Advantageous embodiments are set out in the subclaims.

The invention will be explained in detail with reference to the accompanying drawing, in which:

• Figure 1 shows a schematic top view of an assembly according to the invention;
• Figure 2 shows a device for the assembly according to the invention shown in Figure 1;
• Figure 3 shows a detail from Figure 1;
• Figure 4 shows a detail from Figure 1;
• Figure 5 shows an alternative to Figure 3;
• Figure 6 shows a schematic overview of an external control for a method according to the invention; and
• Figure 7 shows a schematic overview of a local control for a method according to the invention.

Figure 1 shows an assembly which is indicated in its entirety by the reference number 1. The assembly comprises a first road sign board 2, a second road sign board 4, and a message sign trailer 6. In this example embodiment, the assembly comprises two road sign boards 2, 4. In general, an assembly can also comprise one road sign board. In this example, the road sign boards 2, 4 are provided over a road 8 by means of a portal construction 10. It should be noted that in this schematic overview, for the sake of clarity, the road 8 and the message sign trailer 6 are shown in a top view, whereas the portal 10 with the road sign boards 2, 4 on it is shown in a front view.

The road 8 comprises lanes, in the form of an emergency lane 12, a first lane 14, a second lane 16 and an exit 18. The first road sign board 2 is provided above the first lane 14 and the second lane 16 and shows information on the direction and/or destinations which the traffic can reach which follows the indicated direction over the first lane 14 and/or the second lane 16, in this example 's-Hertogenbosch and Amsterdam. This information is located on the road sign board 2 during the required usage period. If destinations and/or directions which are indicated on the road sign board 2 change for a lengthy period, this normally means that the entire road sign board is replaced. This defines the end of the usage period even if the board is not at the end of its service life.

The second road sign board 4 indicates a direction or destination, in this case Vught, which can be reached by taking the relevant exit 18. This information is also located on this board during the usage period of the road sign board 4. Conversely, the information on the road sign boards 2, 4 is substantially located permanently on the boards concerned. Permanently means that this information will not be removed during normal use. It may occur that the information concerned does not need to be visible during a temporary period. This temporary period is obviously shorter than the usage period. Due to this interruption, the information contained is not entirely permanently, but substantially permanently, visible.

In order to modify the information shown by the road sign board 2, 4, the message sign trailer 6 is provided with a projector which, in this example embodiment, comprises a laser 20 which is designed to project the at least one symbol on the road sign board 2 and/or 4. This is indicated schematically in Figure 1 by the contour lines of the projection concerned; for the road sign board 2, these are the contour lines 22; for the road sign board 4, these are the contour lines 24. The projected symbols are explained in detail below with reference to Figures 3-5.

Figure 2 shows in detail a rear view of the message sign trailer 6. The message sign trailer 6 comprises a chassis 26. The message sign trailer 6 further comprises positioning means, in this example embodiment wheels 28, which, in a conventional manner, are connected rotatably on their axle to the chassis 26. The message sign trailer 6 also comprises an information board 30, on which, in this example embodiment, it is indicated that a certain destination (Vught) can be reached by following boards with the symbol V. The information board 30 also comprises a text 32, a warning triangle 34 and a frame with signal stripes 36. The information board 30 is pivotably connected in a manner not shown to the chassis 26 around a horizontal axle. Thus, the information board 30 is upwardly pivotable from a transport condition (not shown) to the usage condition shown in Figure 2.

The laser 20 is provided on top of the information board 30. The laser 20 pivots up with the information board 30, so that it is located in the usage condition shown in Figure 2 at a projection height H above a road surface 38. In the example embodiment shown, this height is 3.5 metres.

Figure 3 shows an example of a symbol which is projected by the laser 20 on a road sign board, in this case the road sign board 4. The symbol concerned is a straight line or bar 40. As is customary in the case of, for example, the covering up of the permanent information on a road sign board, a part of the information on the road sign board is still visible. However, the dimensions and luminous intensities of the bar 40 are chosen in such a way that it is clear that the original information on the road sign board 4, in this case the destination Vught, is temporarily not applicable.

Figure 4 shows an alternative symbol which is projected on the road sign board 2 by means of the laser 20. In this example embodiment, the alternative symbol is a V 42. In this example embodiment, this V corresponds to the V on the information board 30. It is thus indicated that the destination Vught temporarily cannot be reached by following the direction which the road sign board 2 indicates. To make the V more conspicuous, use is made in this specific example embodiment of a two-colour laser, whereby the letter V is projected in a rectangle 44 and the colour of the rectangle 44 differs from both the colour of the road sign board and the symbol V 42.

Figure 5 shows an alternative for the projection of one or more symbols on the road sign board 4. In this alternative, a short bar 48 is projected by means of a first laser projection with contour lines 46 over a direction arrow on the road sign board 4, in this case a direction arrow 49 which, in the usage period, indicates that the exit 18 must be taken in order to reach the destination indicated on the road sign board 4. By means of a second laser projection 48, a different arrow 50 is projected on the road sign board 4, in this case a straight-ahead arrow 50 to indicate that the destination indicated on the road sign board 4, in this case Vught, can be reached by following the road 8 in the straight-ahead direction. In this example embodiment, the arrow 50 is projected against a light background 52, said light background having a colour which differs from both the arrow 50 and the normal background colour of the road sign board 4.

It should be noted that on Dutch motorways, from which the road sign boards 2, 4 have been derived, use is made of road sign boards with a substantially blue background colour and usually white permanent information, such as texts and arrows. Tests have shown that green laser light is clearly visible on blue road sign boards of this type, and that laser light of this colour can project clearly recognizable symbols, which can both cover up existing information and add new temporary information to the road sign boards concerned. Alternative colours for the laser are yellow, orange and red. Yellow is a colour recognizable for users for the addition of information, such as an arrow or an alphanumeric symbol.

The method according to the invention is carried out with the aid of an IT structure 100, as shown in Figure 6. The IT structure 100 comprises the laser 20, optionally a camera, in this case a webcam 102, a data communication means in the form of a router/wireless modem 104. The laser 20, webcam 102, and router/wireless modem 104 are provided on and/or in the message sign trailer 6. A data communication means in the form of a wireless modem 106 and a central control unit, in this case a personal computer 108, which is provided with input means (not shown), such as a keyboard and a mouse, and output means such as a monitor 110 and a printer (not shown) is also located at an external location, such as a temporarily erected site hut or office. The IT structure 100 is characterized in that the laser 20 is controlled from an external location, on the basis of images from the webcam 102 or otherwise. The advantage of this is that as few expensive components as possible are present on the message sign trailer 6, and that the symbols which are projected from the message sign trailer 6 can be switched on and off and also modified remotely. Although the embodiment shown is suitable for an automated control of the laser 20, it is also possible to operate the projection direction of the laser 20 manually on the basis of the images from the webcam 102. In this case, the webcam does not need to be connected to the personal computer 108, but can also be directly connected to a monitor.

An alternative IT structure 200 comprises components which are partially comparable to those in the first-described IT structure 100. For the sake of convenience, the relevant corresponding components are indicated by the same reference numbers as in relation to Figure 6. The alternative IT structure 200 differs from that of the previous example embodiment by means of a decentralized or internal control unit 202. The word internal indicates that the internal control unit 202, along with the laser 20 and the optional webcam 102, is provided in the message sign trailer 6. The internal control unit 202 is designed to control the laser 20, on the basis of information from the webcam 102 or otherwise. Optionally, the internal control unit 202 can be supplied with instructions from the personal computer 108. The advantage of this is that one or more message sign trailers 6 can thus be centrally controlled. However, thanks to the internal control unit 202, this is not necessary so that, in a simple example embodiment, the router/wireless modems 104 and 106, and also the PC 108 and its peripheral equipment can be dispensed with.

In practice, it will be required at any time for the information on a road sign board, the road sign boards 2 and 4, to be temporarily modified. Temporarily modified is understood here to mean the covering up of existing information and/or the displaying of new, temporary information. Both the covering up and the displaying are carried out by means of at least one symbol such as a bar, a circle, an arrow, or an alphanumeric symbol. To do this, for example, the laser 20 is set up preferably on a message sign trailer, such as the message sign trailer 6, along the edge of the road 8. This may be on the emergency lane 12, as shown in Figure 1, or on a road partition such as a crash barrier, or immediately next to the road, for example on a verge on an outside of a road partition. The laser is set up here at a distance L from the relevant road sign board 2. Thanks to this distance, the angles at which a possible plurality of symbols are projected above a plurality of lanes 14, 16, will be comparable with one another in such a way that the amount of reflected laser light does not differ significantly for an observer on the road 8. Three hundred metres is a practical distance here, as this is the distance between consecutive portals with matrix boards so that a portal of this type can be prevented from being located between the laser 20 and the road sign board 2, 4. Three hundred metres is also a standard distance between the information board 30 and the road sign board 2, 4 to be modified.

The laser is set up preferably at a height between three and five metres, but more generally this height is chosen within a range from two and a half metres to six metres. This offers a plurality of advantages. Thus, a height of at least three metres, preferably at least four metres, reduces the likelihood of the laser beam 22 being interrupted by a lorry. Furthermore, road sign boards are usually provided with a retro-reflection layer. Light which shines on a retro-reflection layer of this type is largely reflected back in the same direction as the direction from which it shines on the layer. As a result, the reflection of the laser on a road sign board 2, seen from a direction close to the laser 20 itself, is very bright. Thanks to the chosen height of at least two and a half metres, it is highly unlikely that an observer who could be blinded by the reflection will be located in this direction.

The vertical projection angle depends on the height H of the laser 20, the height of the road sign board 2, 4 and the symbol required thereon, and also on the distance L. Generally, the vertical projection angle is substantially horizontal, which is understood to mean angles between -2° and 2°, in particular between -1° and 1°.

One or more symbols are projected during a temporary period on the road sign boards 2, 4. A temporary period is understood to mean a period which is many times shorter than the normal usage period of a road sign board. In particular, the temporary period is shorter than 1% of the usage period. Where a road sign board has a usage period of many years, the temporary period will amount at most to several weeks. The temporary period preferably amounts to a maximum of one week, more preferably this amounts to a weekend, i.e. from Friday evening until early on Monday morning. In an advantageous embodiment, the temporary period is one night. By projecting a symbol at night only, a relatively weak laser 20 can be used.

A laser with adequate luminous intensity is chosen as the laser. In tests carried out at a distance of a maximum of 45 metres, a 2-watt red laser and a 5-watt green laser were used. At a distance L of 150 to 300 metres, a laser is chosen, depending on the colour of the light and the amount of ambient light, with a power from 2 to 12 watts, in particular 5 to 10 watts. In general, a projector for the invention must project a symbol in such a way that the at least one symbol has sufficient sharpness and contrast on the road sign board to provide a road user with information to supplement or correct the permanent information. Within the invention, a single-colour laser can be used, both to cover up information and to add information via an arrow or an alphanumeric symbol. It may be advantageous to embed an arrow or alphanumeric symbol of this type in a rectangle with a different colour, as described above in relation to the example embodiments. However, this is not necessary in order to achieve the advantages of the invention.

The personal computer 108 and/or the internal control unit 202 are loaded with software to control the laser 20. This control may relate to the one or more symbols to be chosen, the luminous intensity of the projection and the direction of the projection. In one advantageous form, the luminous intensity is automatically regulated on the basis of an observation of the amount of ambient light, for example by measuring the amount of reflected ambient light on the road sign board 2, 4 with the webcam 102. The direction of the projection can be automatically set and/or corrected on the basis of the digital images from the webcam 102.

Within the invention, the road sign board displays information relating to directions and destinations which are reachable via the road concerned. Additionally, or alternatively, road sign boards can display other types of information, such as warnings and instructions.