WO2005113899A1

WO2005113899A1 - Dynamic road marking system

Info

Publication number: WO2005113899A1
Application number: PCT/IB2005/051527
Authority: WO
Inventors: Antonius H M. Raaijmakers; Waltherus E. J. Van Gompel
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2004-05-19
Filing date: 2005-05-10
Publication date: 2005-12-01

Abstract

A dynamic road marking system for influencing a flow of traffic that consists of vehicles traveling over a roadway, wherein said road marking system comprises a plurality of road marking units and each road marking unit is provided with a light source for emitting light in the direction of a driver of one of the vehicles, with the special feature that the light source of each road marking unit is elastically suspended in a hole in the roadway.

Description

Dynamic road marking system

The present invention relates to a dynamic road marking system for influencing a flow of traffic that consists of vehicles traveling over a roadway, wherein said road marking system comprises a plurality of road marking units and each road marking unit is provided with a light source for emitting light in the direction towards said drivers of said vehicles. Such road marking systems are known and are used in traffic control systems for marking traffic routes for vehicles, such as roads for cars and other road users. In one of the methods used by traffic planners in their attempts to reduce traffic jams the number of lanes available to traffic moving in a specific direction is increased or reduced, depending on the amount of traffic. An alternative embodiment makes use of a so-called "tidal flow system". In such a dynamic system, the direction of the traffic of multi-lane roads is changed for one or more lanes in accordance with the direction of the main flow of traffic. Other application areas for systems based on the same principle are dynamic road signs (e.g. bus signs), follow-me systems on the basis of moving lights and normal active road studs for increasing safety. A disadvantage of such known road systems is that the road marking units used therein have a limited life span due to mechanical and thermal loads exerted on components thereof, such as a light source and electronic parts on a printed circuit board. It is an object of the invention to obviate this disadvantage of the prior art, more in particular to propose a dynamic road marking system having road marking units which are able to withstand high mechanical and thermal stress. In order to accomplish this objective, a dynamic road marking system of the type mentioned in the preamble is characterized according to the invention in that the light source of each road marking unit is resiliently suspended in a hole in the roadway. Particularly, the light source of each road marking unit is suspended in said hole in the roadway through a resilient material, such as rubber with a shore A hardness of less than 35. In one preferred embodiment of a dynamic road marking system in accordance with the invention the light source of each road marking unit is resiliently suspended in a housing which is rigidly mounted in said hole in the roadway. In a preferred embodiment the light source of each road marking unit is resiliently suspended in a single (separate) unit which is rigidly mounted in the housing, the latter itself being also rigidly mounted in the hole in the roadway. In this way, said unit (functioning as a top part of the housing) and said housing -together with the roadway- form a rigid construction. Traffic impact forces are transferred from said top part through said housing to the roadway itself. Preferably, the housing is glued to (a) wall(s) of said hole, wherein said glue comprises a heat conductive material. In another preferred embodiment of a dynamic road marking system according to the invention the light source of each road marking unit is embedded in a filling material comprising a heat-conductive material. Ideally, the filling material has a flexibility equal to or higher than (i.e. equal to or lower than shore A value) the material used for elastically suspending the light source and associated electronics. In another preferred embodiment of a dynamic road marking system in accordance with the invention the light source of each road marking unit comprises a LED or a series of LEDs. The unit further comprises a printed circuit board or a series of such boards with electronic parts. The invention also refers to a method of manufacturing a dynamic road marking system for influencing a flow of traffic consisting of vehicles traveling over a roadway, wherein said road marking system comprises a plurality of road marking units and wherein each road marking unit is provided with a light source for emitting light in the direction of a driver of one of the vehicles, characterized in that the light source of each road marking unit is elastically suspended in a hole in the roadway.

These and other aspects of the invention will be apparent from and elucidated with reference to the drawings described hereinafter, wherein Figure 1 is an exploded view of a road marking unit according to the invention; Figure 2 is a perspective view of the road marking unit of Fig. 1, but now assembled; Figure 3 corresponds to Fig. 2, with the difference that the road marking unit is mounted in the roadway. Figure 1 is an exploded view of a preferred embodiment of a road marking unit 1 in accordance with the invention, wherein a metal or plastic housing or carrier 2 is rigidly mounted in a hole 3 in the roadway 4 (Figure 3). In said housing 3 a container 5 for electronic parts (such as a driver printed circuit board 6, a LED printed circuit board 7 and a holder 8 for said LED printed circuit board 7) is mounted in the housing 3. Finally, a top part 9 equipped with a series of LEDs is placed on top of said housing 3 by means of screw bolts 10. In Figure 2 the road marking unit 1 of Figure 1 is shown in assembled condition. The light emitted by the series of LEDs is directed outwardly through transparent windows 11. With reference to Figure 3, a groove 12 is provided between the housing 2 and the roadway 4, said groove 12 being filled with glue in order to glue the housing 2 to the inner walls of the hole 3. Said glue comprises a heat conductive material , so that heat from the road marking unit 1 will be dissipated to the roadway 4, thereby extending the life span of the road marking unit 1. The right mounting of the housing 2 also has a positive effect on the extended life-time of the road marking unit 1, as mechanical stress (caused by vehicles driving over said unit 1) is also compensated by the surrounding roadway 4. A light source in the form of a series of LEDs and the printed circuit boards 6,7 associated therewith are elastically suspended in said metal or plastic housing 2, in which an elastic material (such as rubber) is used between the LEDs and the printed circuit boards 6,7 on the one hand and the housing 2 on the other hand. In order to limit the degree of freedom of movement thereof a filling material with approximately the same elasticity as the elastic material may be used. The filling material comprises a heat conductive material for heat dissipation. The heat conductivity of the filling material and the glue between the housing

2 and the roadway 4 could be typically in the range of 0.03 up to 7 W/mK. The forces induced by traffic tires are in most cases (more than 99%) lower than 4.9 g. Highest force measured is 10 g. These values are much lower than expected on the basis of calculations and simulations. This is due to the high stiffness of the glue in between the unit 1 and the roadway 4. In this way the forces are not only dispersed in the unit 1 itself, but also absorbed by the roadway 4. The forces on the electronic parts are a compromise between acceleration forces and displacement forces. 1. Acceleration forces The forces on the electronic parts (read life expectancy of the electronics) are dependent on the maximum acceleration of the components on the board(s) 6,7. The forces are dependent on the natural frequency and the muffle of the system consisting of the soft filling material and the holder 8. The preferred range for the frequency is 0 to 70 Hz maximum; corresponding acceleration is in the range of 0 to 0.2 g. A typical frequency is 20 Hz, which corresponds with a force of 0.1 g

2. Displacement forces A contra productive effect is the displacement. This should be smallest possible. In this case a frequency of 20 Hz or more is preferred. For example at a frequency of 10 Hz, the maximum displacement is ~ 5 microns. At frequencies higher than 20 Hz the displacement is lower than 2 microns. The relative movement itself is dependent on the softness (suspension constant) of the holder (8) and the filling material. As observed, the relative displacement is higher if the suspension is larger. The suspension characteristic of the materials is dependent on the hardness of the filling material and the holder 8. A range for the hardness is between 10 and 40 Shore A.

A typical hardness could be of the order of 30 Shore A (12 Shore B). The E modulus in this case is in the range of 12 N/mm2.

Claims

CLAIMS:

1. A dynamic road marking system for influencing a flow of traffic that consists of vehicles traveling over a roadway, wherein said road marking system comprises a plurality of road marking units and each road marking unit is provided with a light source for emitting light in the direction towards said drivers of said vehicles, characterized in that the light source of each road marking unit is resiliently suspended in a hole in the roadway.

2. A dynamic road marking system according to claim 1, wherein the light source of each road marking unit is suspended in said hole in the roadway through a resilient material, such as rubber.

3. A dynamic road marking system according to claim 1 or 2, wherein the light source of each road marking unit is resiliently suspended in a housing which is rigidly mounted in said hole in the roadway.

4. A dynamic road marking system according to claim 3, wherein the housing is glued to a wall of said hole.

5. A dynamic road marking system according to claim 4, wherein said glue comprises a heat conductive material.

6. A dynamic road marking system according to any of the preceding claims 1 through 5, wherein the light source of each road marking unit is embedded in a filling material comprising a heat conductive material.

7. A dynamic road marking system according to any of the preceding claims 1 through 5, wherein the light source of each road marking unit comprises a LED or a series of LEDs.

8. A method of manufacturing a dynamic road marking system for influencing a flow of traffic that consists of vehicles traveling over a roadway, wherein said road marking system comprises a plurality of road marking units and each road marking unit is provided with a light source for emitting light in the direction towards said drivers of said vehicles, characterized in that the light source of each road marking unit is resiliently suspended in a hole in the roadway.