Monitoring systems have been installed at Grimselpass near Innerkirchen in the Berner Oberland, Switzerland by ALPUG, an alpine natural hazards research organization. The mountain pass road, a busy tourist route in the summer, lies in the path of potential rock falls. The site consists of two enormous vertical rock plates, roughly 200 m high, with ever-widening cracks at the back. The cracks are opening at a rate of up to 1 mm per day and are already more than 3 m wide. To monitor the rock movement, two Campbell Scientific data loggers are connected by a radio modem to the traffic lights on the main road. If there is a significant increase in the opening of the crack, or the control wires break, an alarm is sent to the lights within 1 second. It is estimated that it takes 30 seconds for falling rocks to hit the main road, so this allows for the lights to stop the traffic going through to the danger area.