Assessment of road-lighting parameters using camera based systems

The basic goal of street lighting is to ensure that a driver can stop or take avoiding action when they see an obstacle. Another goal is the safety and confidence of pedestrians, i.e. they must be able to recognise people at a safe distance, so that there is the potential for avoidance. Camera based measurement methods have been used for many years with a single still photograph and manual analysis of grey values. This has limited use since the road must be measured at many points along its length. An automated system which is able to take account of movement and be calibrated for the road lighting conditions is required. The method requires a calibrated camera, image flow to determine the relative motions, DGPS for position without cumulative error and connection to a street inventory system. The authors discuss camera calibration and error reduction, perspective to planar view conversion, motion determination, and storage of data