Road surfacEs Function for Lighting Evaluation, road marking ContrasT, urban heat Island to ensure VIsibility and sustainabiliTY – REFLECTIVITY

WP 1 : Constitution of a database of road surfaces characteristics

This work package will bring together the characteristics of the samples collected and specifically manufactured, the experimental protocols and the description of the equipment used. This database is expected to feed the modelling and prediction work packages 2 and 3. It will also be made available to all in accordance with the FAIR (Findable, Accessible Interoperable, Reusable) principle and in compliance with the ANR's data management plan.

WP 2: Estimation and prediction of the BRDF of road surfaces

This work package includes the main simulation work carried out within the framework of the project in order to estimate the BRDF of road surfaces and then predict its evolution as a function of the degradation of the surface condition.

- Numerical simulation of the BRDF from the 3D geometry of the surface and a virtual gonioreflectometer: the method consists of digitising the 3D geometry of road surfaces and then estimating the BRDF with a virtual gonioreflectometer as a function of the micro-geometric properties of these surfaces. This will require the use of data structures specific to the simulation of surfaces with complex geometry and appearance to take into account the heterogeneity (diversity of materials) of a pavement. The evaluation of the numerical simulations will be based on the BRDF measurements carried out in the work package 1.

- Prediction of the evolution of the BRDF as a function of the degradation of the surface condition: the objective is to predict the evolution of the BRDF of a road surface as a function of the ageing of the materials (effects of road traffic and climatic conditions) or of the temporary modification of its surface condition (wetting, presence of dirt).

WP 3: In situ and large-scale characterisation of the BRDF of road surfaces

The challenge here is to use field measurements to implement the workpackage 2 in order to

- Carry out numerical simulations of BRDF based on in situ measurements of the 3D geometry of the pavement

- Estimate the albedo of a linear pavement

- Develop relevant indicators for both the pavement and the markings in order to estimate visibility more globally.

The objective is both to carry out a transition to a large scale and also to consider the reflectivity of surfaces for multiple geometries, corresponding to both human vision and the cameras used by automated vehicles.

WP 4: Enhancing the value of BRDF for industry and authorities

Three levers for enhancing the value of the BRDF have been identified.

- Prediction of the optical properties of pavements from their design:

- Optimisation of lighting installations and reduction of urban heat highlands (UHI).

- Management of road markings for all users (human and VA).

The aim of the project is to provide industry and local authorities with a database and new tools for measuring and predicting the photometry of road surfaces. This will allow the optimisation of lighting installations, the reduction of urban heat islands and the respect of safety issues in the context of the arrival of automated vehicles.

- New BRDF laboratory and on-site measurement techniques

- BRDF database for photometric and thermal calculations

- Predictive models :

anticipation of BRDF during the design of a pavement

BRDF evolution according to ageing or surface condition

albedo estimation (from colorimetric measurements, BRDF in the visible range only).

- Vincent Boucher, Valérie Muzet, Paola Iacomussi. MATHEMATICAL CONSIDERATIONS FOR ROAD REFLECTION PROPERTIES. The 30th Quadriennal Session of the CIE, Sep 2023, Ljubljana, Slovenia. PROCEEDINGS of the 30th Session of the CIE, 2023, ?10.25039/x50.2023.PO087?. ?hal-04350013?
- Enoch Saint Jacques, Roland Brémond, François Eymond, Kévin Morvan. INVESTIGATING THE EVOLUTION OF ROAD SURFACE DESCRIPTORS ACCORDING TO OBSERVATION ANGLES USING A DATABASE OF THE REFLECTION PROPERTIES OF URBAN MATERIALS. The 30th Quadriennal Session of the CIE, Sep 2023, Ljubljana, Slovenia. PROCEEDINGS of the 30th Session of the CIE, 2023, ?10.25039/x50.2023.PP020?. ?hal-04349971?
- Valérie Muzet, Guillaume Gublin, Thibaut Rohmer. ON SITE PHOTOMETRIC CHARACTERIZATION OF WET PAVEMENTS. The 30th Quadriennal Session of the CIE, International Commission on Illumination, Sep 2023, Ljubljana, Slovenia. ?10.25039/x50.2023.OP068?. ?hal-04349915?
- Florian Greffier, Christoph Schultze, Vincent Boucher, Sébastien Liandrat, Valérie Muzet. Qd VS Q0 FOR SCALING OF STANDARD R-TABLES IN ROAD LIGHTING DESIGN: THE QUESTION IS WORTH ASKING. The 30th Quadriennal Session of the CIE, International Commission on Illumination, Sep 2023, Ljubljana, Slovenia. ?10.25039/x50.2023.OP008?. ?hal-04250116?

The optical properties of road surfaces are essential to many planning issues, both in urban areas and in the field of road infrastructures. Indeed, the interactions of light with these surfaces underlie important challenges such as the adaptation of cities to climate change or the visibility of road signs whether for the human visual system or for the sensors of driving assistance or autonomous vehicles.

The BRDF (Bidirectional Reflectance Distribution Function) is the function that describes the ability of a surface to reflect a light wave in all directions in space. Although its use is predominant in virtual reality to address issues of visual appearance, it is hardly available for road surfaces (pavement and markings). It is indeed a complex data, in terms of instrumentation and time required to measure it. Thus, in the field of road infrastructures and equipment, very partial data are used by imposing the geometries of observation of the road. Typical pavement characteristics are considered obsolete nowadays and conventional geometries are not very relevant for urban lighting.

The REFLECTIVITY project consortium is composed of three research teams from a Carnot Institute, an industrial company, two university laboratories and two local authorities (urban communities). Its ambition is to demonstrate the importance of the knowledge of the BDRF of the road surfaces to answer the climatic challenge and the development of autonomous mobility. We propose the creation of a shared database describing both the structural characteristics of road surfaces (elementary constituents, formulations, micro and macro textures, surface geometries) and their optical properties (BRDF, photometry, colorimetry, spectral reflectivity). We will develop new techniques to determine the BRDF of road surfaces using in particular a methodology of measurement by virtual gonioreflectometry based on the 3D geometry of the surfaces, usable in laboratory and on road, thanks to the adaptation of existing systems of point or dynamic measurements. The robustness of this approach will be confirmed by comparison with reference measurements made in the laboratory and on site. Accessing the BRDF from dynamic measurements is a technological breakthrough that will allow a large-scale characterization that will consider both the variability and diversity of road surfaces. Temporal evolution aspects will also be addressed via the development of predictive methods of BRDF depending on the formulation of a pavement or a marking but also according to the life cycle of road surfaces by considering the phenomena of ageing of the materials or the evolution of their surface condition (degree of moisture in particular).

In addition to the methodological and scientific aspects of the project, experiments will be conducted with the industrial and the partners cities. They will assess the contributions of the project to the optimization of road lighting installations, to better consider the contrast of markings for the deployment of autonomous vehicles and to provide the albedo of materials for urban climatology. This research will provide a global approach to the optimisation of urban pavements and road markings over large areas, combining daytime and night-time issues and taking into account the diversity of users and environmental conditions.