Traffic detection cable installation

Abstract: Means for installation of traffic detection cables adapted for sub-surface mounting or adapted for top surface mounting which comprises a moulding of prismatic type, that is having the substantially same cross sectional shape extending longitudinally in which two detection cables are embedded, in which the cables are separated to reduce to acceptable levels and/or levels which can be handled by suitable electronic circuitry and/or logic signal processing cross cable interference effects when an impulse is applied to the profile by passage of the vehicle wheels. A void or plate can separate the cables in a matrix of about 85 Shore hardness.

Description: This invention relates to traffic detection cable installations, that is installations of detection cables for traffic monitoring. A typical area of application of the invention is in connection with traffic detector cables extended across roads (see for instance EP-A-287250). The invention in principle can, however, also be employed in other aspects for example on vehicle runways, aircraft carrier take-off pads and in principle any other application where such detection or similar detection will be required. The installation of cables for traffic monitoring presents difficult problems. Traditionally the cables have been stretched across the road surface but the deterioration of cables in service under these conditions can be exceptionally rapid, for example, in dense traffic only a matter of hours, and moreover unpredictable, being dependent upon traffic conditions, speeds of travel and other factors which are difficult to predict. Subsurface mounting of detectors in copper tubes or embedded in channels has been tried, but problems encountered have limited the success achieved. In accordance with a first aspect of the invention there is provided a traffic detection cable installation adapted for sub-surface mounting comprising a moulding having a substantially constant cross sectional shape extending longitudinally, characterised by two spaced and separate detection cables extending longitudinally and embedded in the moulding and a separating means extending longitudinally of the moulding between the cables to separate them to reduce cross cable interference effects, when an impulse is applied to the installation by passage of the vehicle wheels, to acceptable levels and/or levels which can be handled by suitable electronic circuitry and/or logic signals processing. The cables may be embedded side by side, that is of the same depth below the upper surface of the moulding in use, or the cables may be embedded one above the other. The separating means may be provided merely by a sufficient space between the detection cables or by a void space between the cables or an insert of a rigid material between the cables or a rigid insert presenting two parallel longitudinally extending channels in which the material of the profile is provided encapsulating the cable. Preferably the material of the profile is selected to have an elasticity of a suitable kind for detection of impulses with minimal cross cable interference. The material preferably has a Shore hardness of more than 65, more preferably approximately 85. It is desirable that the cables be presented at a depth from the upper surface of the moulding in use which is equal to or more than the depth to which that upper surface of the moulding is adapted to be proud of the surrounding road surface in the installation. In this way if snow ploughs move over the surface of the road, for example, and shave off the upper portion of the moulding the detection cables will not be ripped up or unduly exposed. Preferably, however, the cables are not located near the bottom of the moulding but preferably as near as possible to the upper surface of the moulding having regard to the limitation referred to. In this way the sensitivity of response of the cable is optimised. As an alternative arrangement in accordance with this invention the paired cables are provided in physically separate moulding sub-units adapted to be installed alongside each other, the moulding sub-units being made interlocking so that they can be brought together and installed interlocked with the cables at a reliably established spacing from each other. In this way mechanical interference can be minimised. The manner of locating two cables alongside each other in a moulding can be adapted with this requirements in view. For example polyurethane is a suitable material given the correct specification of elasticity. In accordance with a second aspect of the invention there is provided a traffic detection cable installation adapted for top surface application comprising a moulding having a substantially constant cross sectional shape extending longitudinally, characterised by two spaced and separate detection cables extending longitudinally and embedded in the moulding and a separating means extending longitudinally of the moulding between the cables to separate them to reduce cross cable interference effects, when an impulse is applied to the installation by passage of the vehicle wheels, to acceptable levels and/or levels which can be handled by suitable electronic circuitry and/or logic signal processing; the installation being adapted to be placed on a surface and to allow the passage of vehicles of any kind over it at the surface. A top surface application in accordance with this invention can either be portable or fixed as will be described in detail below. The material of the moulding preferably has a sufficient resilience for the transmission of impulses to the embedded cables. The moulding may be of D profile in shape, the flat surface adapted for resting on a road or other surface and the curved surface for the passage of vehicles over it. Any other profile may be adapted as required including an angular profile approximately to a D profile. The moulding may be provided with longitudinally extending connecting formations to permit a comparably formed moulding to be attached to it. In accordance with an embodiment of this invention a moulding is provided which includes a single cable embedded in it extending longitudinally in the longitudinally extended moulding and adapted to one edge at least or both longitudinal extending edges for joining with a coacting cable moulding containing one or two embedded cables. The embedded cables may be piezo-electric, exhibiting a resistive and/or generative piezo-electric response, tribo-electric or exhibit any other effect including capacitance based effects upon the receipt of a mechanical impulse and/or a physical strain associated with the impulse or stress field generated by the impulse. Installations in accordance with the invention can be provided in a spaced parallel array for speed detection at a distance which is suitable for speed detection purposes. As is known the installations provided can be used in a duplicated measurement system as is prescribed by law in certain countries and is the practice in several others to provide legally sufficient proof of the breaking of speed limits for law enforcement purposes. In an application of the invention there is provided a traffic measurement system comprising three parallel spaced apart installations, the first one to serve as a start cable for measurement, the second one to serve as a stop cable for that first measurement and simultaneously as a start cable for a second confirmation measurement and a third cable to provide the stop signal for the second confirmation measurement. The invention will be more fully described, by way of examples, with reference to the accompany drawings, in which:- Figure 1 is a schematic longitudinal cross section through a road showing three sub-surface installations; Figure 2 is a schematic longitudinal cross section through a road showing two sub-surface installations; Figure 3 is a schematic longitudinal cross section through a road showing two top surface embedded installations; Figure 4 is a schematic longitudinal cross section through a road showing two top surface embedded installations; Figure 5 is a schematic longitudinal cross section through a road showing two top surface embedded installations; and Figure 6 is a schematic longitudinal cross section through a road showing a top surface embedded installation. Figure 1 shows three different installations set in a road. In the first installation a moulding 1 has two cables 2 and 3 located alongside each other at the same horizontal height and a void space 4 between them in the moulding to eliminate cross cable interference. The moulding is of T shape, the upper cross bar 5 of the T being proud of the road surface 6. The cables 2 and 3 are a distance below the top of the moulding slightly more than the thickness of the bar 5 to reduce their exposure to damage. The second installation comprises a moulding 7 which has an extruded aluminium moulding 8 embedded in it and containing the cables which are again designated 2 and 3, other features being marked with the same reference numerals and being similar. The third installation comprises a moulding 9' which has two cables again marked 2 and 3 but this time mounted one above the other and with a simple metal strip 9 between them to eliminate inter-cable interference. Again other features have the same reference numerals and correspond with the description of the first installation. Figure 2 shows an array of installations comprising two paired sets of extruded moulding sub-units 10, 11 and 12, 13 each having interlocking formations 14 and 15 to keep them together. One cable 16, 17, 18 and 19 respectively is provided in each moulding sub-unit. As shown in Figure 3 there is provided an array comprising a longitudinally extending moulding 31 having a single cable 32 in it and in a spaced parallel relationship to it a longitudinally extending installation comprising a moulding 33 having two cables 34 and 35 embedded in it. These are placed on a road surface 36 and for example they may be tensioned on a road surface and optionally in addition or instead also bonded to the road surface by use of a suitable bonding material or glue or adhesive suitably adapted to the nature of the road surface. The base of the moulding may be reinforced by the embedment of sheet material such as sheet material and/or polymeric sheets or fibrous mats or webs, both polymeric textile webs or bands or belts and metallic woven webs and bands or belts. It is desirable to preserve the facility for this article to be rolled up and thereby stored conveniently. It may be noted in the experience of the applicant that in certain traffic conditions unprotected piezo-electric cables stretched over a road surface cannot be relied upon to last a long time and may last a quite variable period between a few hours, a few days to a few weeks or in favourable conditions significantly longer. It is thus an object of this invention to provide a better installation of surface cables. Figure 4 shows two installations comprising mouldings 37 and 38 each containing embedded cables 39, 40, 41 and 42 respectively and in a spaced array on a road surface 43. This duplication of cables can provide for the duplication of speed read-outs as is required in certain jurisdictions for evidential verification for speed law enforcement purposes. Figure 5 shows two installations in accordance with the invention in a spaced array each comprising a moulding sub-unit 44 and a moulding sub-unit 45 which have interlocking formations along one longitudinally extending edge which are shown here interlocked as at 46, each moulding sub-unit containing an embedded cable 47 and 48 respectively. Again reinforcing foils, belts, webs, textiles or bands 49 can be provided as shown in all figures. Figure 6 shows on an enlarged scale an installation comprising a moulding 57 having an embedded textile belt 58 and two piezo-electric cables 59 and 60 of coaxial type. An adhesive 61 is provided on the lower surface for gluing to the road.

Claims: A traffic detection cable installation adapted for sub-surface mounting comprising a moulding (1) having a substantially constant cross sectional shape extending longitudinally, characterised by two spaced and separate detection cables (2, 3) extending longitudinally and embedded in the moulding and a separating means (4) extending longitudinally of the moulding between the cables to separate them to reduce cross cable interference effects, when an impulse is applied to the installation by passage of the vehicle wheels, to acceptable levels and/or levels which can be handled by suitable electronic circuitry and/or logic signals processing. A traffic detection cable installation adapted for top surface application comprising a moulding (37) having a substantially constant cross sectional shape extending longitudinally, characterised by two spaced and separate detection cables (39, 40) extending longitudinally and embedded in the moulding and a separating means (4) extending longitudinally of the moulding between the cables to separate them to reduce cross cable interference effects, when an impulse is applied to the installation by passage of the vehicle wheels, to acceptable levels and/or levels which can be handled by suitable electronic circuitry and/or logic signal processing; the installation being adapted to be placed on a surface and to allow the passage of vehicles of any kind over it at the surface. A traffic detection cable installation as claimed in Claims 1 or Claim 2, in which the cables are embedded side by side in the moulding at the same depth below the upper surface of the installation in use. A traffic detection cable installation as claimed in Claim 1 or Claim 2, in which the cables are embedded in the moulding one above the other. A traffic detection cable installation as claimed in any one of Claims 1 to 4, wherein the separating means is a void space (4). A traffic detection cable installation as claimed in any one of Claims 1 to 4, wherein the separating means is an insert (8, 9) of a rigid material. A traffic detection cable installation as claimed in any one of Claims 1 to 4, wherein the separating means is a rigid insert (8) presenting two parallel longitudinally extending channels in which the cables are located. A traffic detection cable installation as claimed in any one of Claims 1 to 7, in which the material of the moulding is selected to have an elasticity of a suitable kind for detection of impulses with minimal cross cable interference. A traffic detection cable installation as claimed in Claim 8, in which the material has a shore hardness of more than 65. A traffic detection cable installation as claimed in Claim 8, in which the shore hardness is approximately 85. A traffic detection cable installation as claimed in Claim 1 or in any one of Claims 3 to 10, insofar as they refer to Claim 1, in which the cables are presented at a depth from the upper surface of the moulding which is equal to the depth to which that upper surface of the moulding is adapted, in use, to be proud of the surrounding road surface. A traffic detection cable installation as claimed in any one of Claims 1 to 11, in which the cables are provided in separately formed mouldings sub-units (10, 11) adapted to be interlocked together for installation. A traffic detection cable installation as claimed in Claim 2 or any one of Claims 3 to 10 or 12, insofar as they refer to Claim 2, in which the moulding is of approximately D profile in shape, the flat surface adapted for resting on a road or other surface and the curved surface for the passage of vehicles over it. A traffic detection cable installation as claimed in any one of Claims 1 to 13, in which the embedded cables are piezo-electric, exhibiting a resistive and/or generative piezo-electric response, tribo-electric or exhibit any other effect including capacitance based effects upon the receipt of a mechanical impulse and/or physical strain associated with the impulse or stress field generated by the impulse. A traffic measurement system comprising three parallel spaced apart installations each in accordance with Claim 1 or Claim 2, the first being a start cable for measurement, the second being a stop cable for the first measurement and simultaneously being a start cable for a second confirmation measurement, and the third cable being a stop cable for the second confirmation measurement.

Inventors: GEBERT FRANZ JOSEF, GEBERT RALF DIETER HEINRICH, GEBERT RUDIGER HEINZ, GEBERT, FRANZ JOSEF, GEBERT, RALF DIETER HEINRICH, GEBERT, RUDIGER HEINZ
Applicants: GEBERT FRANZ JOSEF, GEBERT RALF D H, GEBERT RUEDIGER HEINZ, GEBERT, FRANZ JOSEF, GEBERT, RALF DIETER HEINRICH, GEBERT, RUDIGER HEINZ
Application year: 1990
Main classification: G08G1
IPC codes: G08G1, G02B6