Photoelectric sensors monitor vehicle heights in windy and bad weather

  • Ein robustes Metallgehäuse und die beheizbare Optik sind zwei wesentliche Merkmale der Einweg-Lichtschranken LS 96 von Leuze electronic. Das Ingenieurbüro Keller hat Ausricht- und Abdecksysteme für diese Anwendung konstruiert.

  • Die robust ausgeführten Einweg-Lichtschranken LS 96 von Leuze electronic erfüllen auch an der Autobahn die Anforderungen bei jeder Wetterlage. Redundant installiert gewährleisten diese Einweg-Lichtschranken auch im Freien maximale Funktionssicherheit.

  • Mechnische Systeme können bei Kollision leicht beschädigt werden, ein mehrmaliger Austausch im Jahr aufgrund von Beschädigungen ist nicht selten. Zudem sind sie im Vergleich zu optischen Lösungen kostenseitig stark im Nachteil.

  • Die vom Ingenieurbüro Keller an den Säulen der Schilderbrücken installierten Einweg-Lichtschranken LS 96 von Leuze electronic übernehmen die Funktion der rot-weissen Aluminiumleisten – hier an der Einfahrt des Pörzberg Tunnels, der die neue Ortsumfahrung Schaala bei Rudolstadt bildet.

Traffic safety with Leuze electronic

Throughbeam photoelectric sensors monitor vehicle heights

Originally, overheight monitoring for trucks in the "Berg Bock" highway tunnel was done by mechanical systems. But the aluminum rails damaged by vehicle impact had to be repaired or exchanged every time. A new solution which prevents this is based on the functionality of Leuze electronic throughbeam photoelectric sensors.

When Antenne Thüringen reports of a traffic jam on the A71 in the area of the Suhl highway interchange and the Suhl/Zella-Mehlis connection, the cause could be a closure of the "Berg Bock" tunnel which is located in between – possibly produced an overloaded or extra-long vehicle. Throughbeam photoelectric sensors from Leuze electronic series LS 96 prevent this situation from getting any worse (Figure 1). They are mounted to sign gantries or measuring bridges a few hundred meters from the entrances to the tunnel and always trigger a closure when an overheight vehicle trips the infrared light beam (Figures 2a/b).

Mechanical systems have weaknesses

Originally, overheight monitoring in the "Berg Bock" highway tunnel was done by mechanical systems. The red and white aluminium rails, visible from a distance, were mounted in such a way that they could teeter to the side if an overheight vehicle drove by (Figures 3a/b/c). The signal which this simultaneously triggered leads to a closure in front the tunnel portals via a signaling system. According to the Thuringia State Office for Construction and Transportation, these incidents happen several times a year - and the aluminum rails damaged by vehicle impact had to be repaired or exchanged every time! Due to the costs connected to this, a long-term economical solution which also had to be reliable and largely maintenance-free was sought with the help of local engineering firm Keller. Bernd Keller, who primarily works in controller manufacturing and switching cabinet manufacturing from Zella-Mehlis saw a solution to this problem in the functionality of throughbeam photoelectric sensors such as are, among others, used in plant engineering and automation. Supported by the sensor people at Leuze electronic and after extensive experiments, series LS 96 proved itself to be most optimally suited to the task.

Optical solution from Leuze electronic

The throughbeam photoelectric sensors consist of transmitters and receivers which are mounted at a height of 4.5 m, across from each other on the columns of sign gantries. The robust metal housing with glass covers with protection rating IP 67 or IP 69K are designed for industrial use and fulfill the requirements on the highway for every type of weather. The infrared light in particular ensures high functional reliability and increased indifference to ambient light e.g. direct sunlight. Thanks to their optics heating, the devices are also armed against snow and ice at low temperatures down to -35 °C. "Furthermore, the device version with an operating range limit up to 150 m features sufficient performance reserve to bridge distances of 20 to 25 m between transmitter and receiver interference-free, depending on the number of lanes", added Keller.

Redundancy guarantees reliability

So that leaves, birds or other types of disturbance don't lead to faulty operation, induction loops are embedded into the lanes. In addition to the throughbeam photoelectric sensors, they detect every vehicle in the lanes. Moreover, the Light Beam Devices are installed in pairs. This redundancy ensures that every overheight vehicle is detected, and Antenne Thüringen won't have to report traffic jams caused by tunnel closures due to overheight vehicles.

Further tunnels optically safeguarded

The advantages of the optical system are obvious. Therefore, four additional high monitors with eight pairs of LS 96 (transmitter and receiver) were implemented by Keller at the entrances of the Pörzberg Tunnel, the new Schaala local bypass near Rudolstadt (Figures 4a/b).


  • Branch/Area

    Building/transportation industry

  • Duty

    Object protection, Presence inspection

  • Application

    Photoelectric sensors monitor vehicle heights in windy and bad weather