The Railway Technical Research Institute (RTRI) has developed a new obstruction detection device for level crossings that registers previously undetectable objects such as pedestrians, two-wheeled vehicles, and wheelchairs. A range of external disturbances appear in outdoor images, such as changes in brightness between day and night, changes in sunlight intensity, shadows, car headlights, rain, snow etc. A stereo camera was therefore adopted to suppress the influence of such external disturbances so that only obstructions on the railway crossing itself are detected. This is done by measuring the three-dimensional shape of an object in a way similar to human vision (Fig. 1).
      To improve the outdoor detection rate, a neutral density filter drive mechanism is incorporated into the camera to prevent noise, or smear, in CCD elements. Insertion and removal of the filter can be controlled automatically. A 2-step shutter control mechanism is also provided for alternate short and long-exposure photographs to enable simultaneous detection of dark and bright objects. A performance test carried out on a JR commercial line temporarily set up with this device (Fig. 2) showed a detection rate for automobiles of 99% or more by day and 98% or more by night, and 97% or more for two-wheeled vehicles and pedestrians (Fig. 3). Attempts will be made to raise the detection rate by improving the detection logic, and to reduce costs (including construction) to or below those of the current photoelectric system to enable practical use as an obstruction detection device.
      This development was conducted with a subsidy from the Ministry of Land, Infrastructure and Transport.