The line scan data was acquired through a single channel of the multiplexed 13-channel on-chip analogue-to-digital converter, configured for 10-bit, 500 ksps operation. At 500 ksps operation, a single sensor read of 512-pixels took a time of 1.024 ms and this was a hardware-related limitation for operating the PDU at higher speeds. This is because four sensor reads are performed on a per scan basis amounting to a total sensor access time of 4.096 ms, which, after factoring in the processing time required by the discrimination algorithm, effectively limits the current vehicle speed at which the prototype PDU can operate, to around 3.5 km/h