Railway vehicle wheel detection apparatus and method

The presence of a railway vehicle wheel (fig.2,60) on a section of rail (fig.2,50) supported by adjacent rail supports (fig.2,70) is determined by a wheel detector 11 and the result indicated by an output controller 13. The detector is configured to employ measurements from a Wheatstone bridge strain gauge sensor 2, obtaining measurements of shear strain in a vertical direction at a single measurement location, within or on the surface of the rail web, preferably midway between the supports, without any measurements from another location. The wheel detector may have at least one comparator. Preferably, a first comparator 111 compares the magnitude of a positive input signal with a first predetermined threshold value, and a second comparator 112 compares a negative input signal with a second threshold value, outputting the results to the output controller. The output controller may switch off respective output signals for a period should the magnitude of the input signals exceed their threshold values, and for an additional delay period after the input signal drops below the threshold value. The wheel detector may also be configured to determine the direction of travel of the train. Additional signal conditioning circuitry 12 may amplify the sensor measurement signals.