How road surfaces reflect light in space is a physical characteristic that plays a key role in the design of road lighting installations: by European Standards the average luminance is the target quantity to assure the required safety conditions of the motorized road traffic. Lighting systems are designed (luminous flux installed per kilometre) to comply with the above requirement, starting from reference values of road surfaces reflection published in an old scientific document. These data are obsolete and not representative of current road surfaces, but they are still used to design current LED lighting systems. European Community funded a SURFACE project to provide to EU standard organization new traceable reference data, representative of current road surfaces used in EU. The paper presents the data collections and the impact on road lighting of using available old reference data versus SURFACE collected data of current road surfaces. Results highlight advantages in using bright pavements as well the need for introducing systems for flux control in road lighting installation to compensate for the discrepancies between current reference data and actual road surface data.

Specifications concerning road lighting and photometry of road surfaces were established more than 50 years ago. Road lighting design and road marking visibility were developed for vehicle driving. The observation distance defined by standards corresponds to interurban applications; however, within Europe these areas do not tend to be lit. The objective of the SURFACE project is to propose new geometries for the photometric characterisation of pavements, both adapted to different urban travel modes and new lighting technologies. This article reviews the available guidelines, standards, measuring devices and literature regarding geometries and road lighting applications, and presents the project SURFACE analysis and proposal. The SURFACE consortium recommends adding several new angles for different driving conditions and road users; 2.29° for urban environments and consistency with road marking standard, and 1° for extra-urban environment and consistency with previous geometries. A 5° angle, corresponding to 17-m viewing distance, could be an interesting compromise, suitable for urban driving at low speed, cycling and for scooters. The angles of 10° and 20° are under consideration for describing the boundary between diffuse and specular behaviour.

Optimization of lighting installations should be a priority in order to reduce energy consumption and obtrusive light while providing optimal visibility conditions for road users. For the design of lighting installations, it is assumed that the road has homogeneous photometric characteristics and only one viewing angle is used. There are often significant differences between the design of lighting installations and their actual performance. In order to examine whether these differences are due to the photometry of the road, this study proposes metrics to assess the influence of road heterogeneity and observation angle. These metrics have been used on many measurements conducted on site and in the laboratory for different pavements. A calculation engine has been developed to realize road lighting design with several r-tables in the same calculation or for different observation angles. Thus, this study shows that a root mean squared deviation (RMSD) calculation, including average luminance and uniformities associated with different r-tables, is directly correlated to a normalized root mean squared deviation (NRMSD) calculation between these r-tables. With these proposed metrics it is possible to optimize lighting installation while taking into account different types of urban surfaces and the diversity of users.

In this study, the photometry of a wide range of conventional and innovative pavements used in urban and interurban areas was characterised with a laboratory gonioreflectometer, both in new condition and after 30 months of natural ageing. An extreme diversity of behaviour with respect to light reflection has been demonstrated, both over time and between pavements. Various lighting studies have been carried out for cases of renewal of lighting installation with the installation of LED luminaires on poles in place. The calculations have shown that the use of typical CIE r-tables almost systematically leads to non-compliance with the EN 13201 standard, particularly in terms of uniformity. On the other hand, taking into account in the calculations, the photometry of the pavement in its stabilised state makes it possible both to respect the challenges of lighting safety and to achieve significant energy savings. As measurements of pavement photometry are rarely carried out, an alternative is to set up a database of urban pavements, which is one of the achievements of this research.

The forthcoming arrival of automated vehicles (AV) on the roads requires the re-evaluation or even adaptation of existing infrastructures as they are currently designed on the basis of human perception. Indeed, advanced driver-assistance systems (ADAS) do not necessarily have the same needs as drivers to detect road markings. One of the main challenges related to AV is the optimisation of the vehicle–infrastructure pair in order to guarantee the safety of all users. In this context, we compared the performance of a vehicle equipped with an ADAS machine-vision system with a dynamic retroreflectometer during the daytime on a road section. Our results questioned the reliability of the literature thresholds of the luminance contrast ratio on a dry road under sunny conditions. Despite the presence of old and worn road markings, the ADAS camera was able to detect the edge lines in more than 90% of the cases. The non-detections were not related to the poor condition of the markings but to the environmental conditions or the complexity of the infrastructure.

This paper addresses both geometrical definitions and a methodology of computation of the average luminance factor. The road lighting community deals with a dedicated coordinate system adapted to the different lighting situations. The road surface characterisation is used both for the road lighting and road marking community and is also useful for visual appearance models that use Bidirectional Reflectance Distribution Function (BRDF). In this paper, conversion relations are given between BRDF and road/marking lighting conventions. The second issue deals with the calculation of the average luminance coefficient Q0 defined in CIE 144:2001 for road surface characterisation. The calculation has been defined in the seventies and its explanation cannot be found as it has not been published. The paper proposes a new definition of the solid angle for the integration that provides the best compromise between mathematical rigour and previous customary approach.