Life E-VIA: Prototypal Low-Noise Road Surface for the Reduction of Electric Vehicle Rolling Noise in Urban Area

Abstract

In both the current and foreseen context of significant development of the electric vehicle (EV) fleet, a future increasing ratio of EVs in the urban traffic is expected, still enhanced in low-emission zones involving bans or restricted access to other vehicles. EVs are known to be quieter than conventional vehicles at low speed because of a low motor noise emission, resulting in a higher prevalence of rolling noise in the environmental noise. EVs differ from conventional vehicles in several parameters that can influence tyre/road noise, like weight and torque. The LIFE E-VIA project objectives consist in developing, implementing and assessing a low-noise road surface for light EV traffic in urban conditions, optimised from an acoustical and life cycle perspective. In parallel, an optimisation of EV tyres is investigated. Prior to forthcoming layout in Florence (Italy) for assessment under real traffic conditions, a prototypal road surface has been implemented and evaluated on a test track in Nantes (France). Preliminary tests carried out with different EVs on several road surfaces highlighted the variability of noise emission over vehicle types and pavements, leading to specific ranking. Two prototype versions of a low-noise road surface have been laid out in Nantes, respectively without and with crumb rubber. Both of them have been acoustically assessed with on-board microphones (CPX method) and at roadside (CPB method and microphone array). Constant speed, acceleration and deceleration conditions were considered for pass-by tests. Other acoustical or physical parameters have been measured: acoustic absorption, 3D-texture, mechanical impedance and skid resistance properties (BPN and MPD). In comparison with a reference DAC 0/10 road surface, very usual in France, a roadside noise reduction up to 4 dB(A) was found at steady pass-by speed 50 km/h. Grip values are very high and macrotexture levels moderate. Lastly, mixtures durability is analysed with laboratory tests.

Factors influencing tyre/road noise under torque

“…Studies have shown that this effect increases further with acceleration, i.e. with tyre torque [3]. Even though also characterized by the occurrence of torque, for normal braking and recuperation, in contrast, only small changes have been observed [4].…”