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REFLECTIVITY project

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

Context

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

BRDF (Bidirectional Reflectance Distribution Function) is the function that describes the ability of a surface to reflect the light in all spatial directions. Although its use is predominant in virtual reality to address issues of visual appearance, it is very rarely available for road surfaces (road surfaces and markings). It is indeed a costly data, in terms of instrumentation and the time required to measure it. Thus, in the field of road infrastructure and equipment, very partial data are used by imposing fixed road observation geometries. These practices are now considered obsolete and conventional geometries are not very relevant to represent the diversity of road users and public spaces.

Project goals

The REFLECTIVITY project aims to develop tools and methodology for measuring and predicting the BRDF of road surfaces. Its originality lies in its global approach, which takes into account both daytime and night-time aspects, all users and multi-scale aspects (both spatial and temporal).

Its objectives are to:

Determine the BRDF (function that characterises the reflectivity of a surface for all illumination and observation directions ) by both :

  •     Measurements on samples and in situ conditions
  •     Numerical simulations for BRDF prediction (virtual gonioreflectometry)
  •     Large-scale characterisation (street, neighbourhood, city), even at high speed.

Predicting the optical properties of pavements and markings

  • From pavement formulation
  • According to their evolution over time, considering ageing under the effect of climatic constraints and road traffic
  • According to temporary deterioration, taking into account weather conditions (wetting of the surface) or the effects of dirtiness.

Promote the use of complete BRDFs for

  • Optimisation of public lighting installations
  • Albedo estimation for UHI reduction
  • Management of road markings for all users (human and VA).

Expected outcomes

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.

Applications

  • Dimensioning of urban developments, decision support
  • Diagnosis of the optical properties of pavements by instrumented vehicle
  • Public lighting: energy optimisation, integration of specific uses, limitation of light pollution, smart-lighting
  • Urban climatology: limitation of UHI
  • Road infrastructures: performance and visibility of markings for the human visual system and the VA sensors

Main
results
expected

  • 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).

Project
organisation

Project
Productions