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Sensor Line Fiber Optic Traffic Sensors for Axle Detection

Sensor Line

Sensor Line is the world’s leading company providing fibre-optic (FO) load sensors for rail and airport traffic.

Sensor Line’s proprietary FO technology ensures a unique performance for axle detection regardless of whether the installations are performed in slots or frames. The FO traffic sensors work for any vehicle speed, on any pavement and with the highest reliability, accuracy and durability. Sensor Line’s traffic sensors are highly elastic and adapt perfectly to changing rail conditions. Sensor Line’s FO traffic sensors play an important role in toll applications, because of their longevity and accuracy. Their static response also simplifies dual-tire detection often required in toll classification schemes. Whenever it comes to reliable and accurate axle detection, Sensor Line’s FO sensors are the best choice.

FO traffic sensors are available as naked SPZ sensors, pre-casted PUR Sensors or as polymer frame based EZ Treadles in any sensor and cable lengths. They work over a wider range of speeds than any other axle sensors. They have a static response, so they can detect stationary loads on the sensor. Sensor Line’s axle sensors also deliver exceptionally clean signals and are unaffected by electromagnetic interference.

SPZ fibre-optic traffic sensors

Slot installations of our SPZ FO sensors are the most economic method for superior axle detection. SPZ sensors are available with standard cables up to 100m. Properly installed in our resin family SL CAST-80/90, those sensors work with the highest accuracy and for an unlimited number of axle loads.

PUR Sensors

Sensor Line’s FO sensors are now available as pre-casted and reinforced PUR sensors which additionally increase the uniquely long lifetime. The simple installation reduces the installation risk to nearly zero. The attached hanger bars allow a perfect surface levelling over the lengths, which ensures perfect axle/wheel detection. PUR sensors work as perfect switches for any speed and with a durability a few times higher than any other state-of-the-art treadle technologies. Based on that technology, any other state of the art treadles strips can be copied and replaced.

EZ Treadles

Sensor Line’s polymer frame-based sensor solution EZ Treadles is available for any sensor configuration and lengths and will directly be installed in concrete surfaces. This solution can also be used as treadle inserts, which fit in TRMI or IRD frames and are available upon customer request as two, three or four channel versions.

The complete frame is fixed with special reusable stainless bolts. A strip replacement can easily be performed within a few minutes if a single strip should fail to work.

Therefore, single EZR replacement strips should be in stock, which could be installed at site with simple means. The lab-manufactured and reinforced EZ Treadles and EZR strips guarantee that the tires always deform the sensors sufficiently, resulting in 100% detection accuracy. The great wall strip bonding and reinforcement in lengths also ensure lowest stress and therefore the highest possible lifetime.

Surface-mounted fibre-optic sensors

Surface-mounted fibre-optic sensors are ideal for dual lane traffic-data acquisition. A steel-enforced plastic sensor base allows insertion of long sensors for independent monitoring of up to two neighbouring lanes. The sensor design avoids any cross-talk and provides reliable lane selective axle information.

Optical transmittance analysers

Sensor Line’s MA-110, MA-210 and MA 310 dynamic interfaces operate up to three FO sensors and deliver highly reliable and accurate digital trigger signals if a certain adjustable relative change of light has been detected. The two-channel static MD-220 optical transmittance analyser operates two FO traffic sensors in a wide dynamic range and is recommended for dual-tire detection applications.

The MA-110, 210 and 310 devices are dynamic interfaces, making them ideally suited for highly reliable axle detection and speed measurement. These devices make our static sensors quite dynamic but they still detect low speeds. However, they do not store static information as in axles resting within dual tire sensor configuration.

The MD-220 series is a micro controller-based interface and operates two FO traffic sensors down to zero speed. Besides real time triggering via digital optocouplers output stages, it also includes a RS 232 interface and supports serial data system integration, as well as easy laptop diagnostics, with our VIEW220 and MD-View signal viewing software. The housed MD-220 series meets the European CE standard.

Embedding resin and filler materials

Sensor Line offers products for different installation techniques. Each method has other requirements and therefore different embedding materials have to be applied. For SPZ sensor slot installations the highly elastic and well-bonding SL CAST 80/90 resin family has been well proven and has become a SL standard product for nearly ten years. PUR sensors are encapsulated in SL CAST-90 and normally need different and harder slot filler materials.

The ‘PU 200’ material from Global Resin, UK, can be used for asphalt; cement-based filler materials such as the ‘V2/40’ from Pagel Group are well proven for concrete surface installations, but other locally available and suited materials can also be considered. The polymer frame based EZ treadles can only be installed in concrete lanes; therefore materials such as ‘V2/40’ or ‘FlexKrete 102’ will be an excellent choice.

Automatic vehicle detection and classification

CLASSAX is an automatic vehicle detection system and available for full or half-CLASSAX sensor configuration. Full-CLASSAX sensor configuration additionally picks up all lateral vehicle parameters such as inner and outer wheelbase, as well as tire widths and lengths. HALF CLASSAX classifies based on axle amount, axle spacings and groups. If a loop instead of an OVD is used for presence detection, we will process the loop signature as well. Additionally, we can feed in two bits to correlate heights to any axle if required.

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Press Release

Sensor Line Wins Stifterverband Innovation Award

Seal of approval innovation award 'innovative through research' awarded by the Stifterverband.

White Papers

Fibre-Optic Traffic Sensors

Fibre-optic axle sensors work over a wider range of speeds than any other axle sensor. They have a static response, meaning they detect stationary loads on the sensor.

Sensor Line GmbH

Carl-Poellath-Strasse 19

86529 Schrobenhausen


+49 8252 8943-0 +49 8252 8943-11

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Products and Services


Press Release

3 July 2018

Seal of approval innovation award 'innovative through research' awarded by the Stifterverband.

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6 September 2016

Sensor Line, one of the leading global suppliers providing fibre-optic load sensors for the road traffic, railway and airport industries, will be present at InnoTrans 2016 to display their latest fibre-optic products and solutions.

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8 February 2010

Sensor Line, the world's first company providing fibre-optic (FO) load sensors for road, railroad and airport traffic, has introduced a new concept for automatic vehicle detection classification (AVC) and traffic data collection, combining the advantages of axle sensors with those of an indu

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5 October 2006

CLASSAX is a new concept for automatic vehicle detection, Automatic Vehicle Classification (AVC) and traffic data collection, combining the advantages of axle sensors with those of an inductive loop instead of considering both detection principles to be competing. A CLASSAX system is ca

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Regional Offices

Sensor Line GmbH

Carl-Poellath-Strasse 19

86529 Schrobenhausen


+49 8252 8943-0 +49 8252 8943-11

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