Condition assessment of road equipment - State-of-the-art

Road equipment is used for increasing safety and comfort in traffic. There are 5 main groups of equipment: road lighting, fences and barriers, vertical signs, horizontal signs and traffic signals. Common for all road equipment is that, once they have been installed on the road, the performance must be maintained. Condition assessment is an important tool for determining the maintained degree of performance. Generally, there is a large number of equipment along a road. This means that a measurement method must be fast and practical to use. Even so, not all equipment can be measured, but a sample must be chosen from the population. In other words, condition assessment needs both sampling and an appropriate measurement method. In practice, sampling in-situ can be difficult to perform. Consequently, it might be necessary to deviate from complete randomness when sampling. However, it is important that sampling is carried out in such a way that no systematic errors are introduced. A physical measurement method aimed for condition assessment should preferably be mobile. Unfortunately, only a few mobile methods are described in the literature and, among these methods, solely one physical method has been used for assessment (road marking retroreflectivity characterization). Results from such studies have been published in USA and the Nordic countries. Although the lack of mobile instruments, condition assessments of street lighting, rails, noise shields, glare shields, road signs, raised pavement markers and traffic signals have been documented. Such studies have been carried out using stationary instruments or by a subjective judgement. It is known that quality control improves performance, which has, for example, been documented in a Swedish 6-year study on road markings. Consequently, if checks of road equipment are carried out regularly, there is a reason to believe that this control would improve the road equipment performance, which, in turn, would be a benefit, not only for the road keeper but also the driver. Therefore, development of mobile instruments aimed for all types of road equipment is desirable.