The Characterisation of Road Surface Friction as a Factor in Vehicle Safety

  • Peter Sanders

Student thesis: Doctoral Thesis


The relationship between road surface friction and vehicle safety is self evident. This relationship means that the effective management of friction is critical in maintaining a safe environment for all road users. Many road authorities measure low speed friction with devices utilising the sideway-force measurement principle, and assess texture depth as a proxy for high speed friction.

This thesis concludes that whilst effective for a time, road surface friction management policies based on measurements made by sideway-force devices are in need of radical reform in order to achieve a link between the management of road friction and vehicle safety.

This conclusion is of particular significance to the Australian, Belgian, Czech, English, French,
German, Hungarian, Irish, New Zealand, Northern Irish, Scottish, Slovenian, Spanish, and Welsh, road authorities but will also be of interest to other authorities currently using, or investigating the use of, sideway-force friction measurement devices.

This thesis presents the results of a decade of study into road surface friction characterisation and how it pertains to vehicle safety. Six research reports are presented which detail:
• the relationship between road surface properties and the generation of tyre / road friction;
• a statistical model for predicting the friction generated between a road surface and tyre at all possible friction parameters; and
• an assessment of sideway-force devices to determine their measurement parameters.

Chapter 7 of this thesis presents an alternative friction management policy based on the use of crowd sourced in-vehicle data, which has undergone a promising proof of concept study.

This thesis demonstrates a correlative, and causal, disassociation between the friction parameters exploited by road vehicles, and those measured (or inferred) for engineering purposes on the English trunk road network. This disconnect is a significant and unique finding which supports the main conclusion of this thesis.

This thesis also demonstrates the need to include advanced research methodologies into road friction research portfolios, such as, the application of a multivariate approach to the prediction of friction between a tyre and road surface, or the use of advanced statistical methods such as artificial intelligence or machine learning to identify influencing factors not currently understood.
Date of AwardMar 2022
Original languageEnglish
SponsorsTRL Limited & National Highways
SupervisorDavid Woodward (Supervisor), William Rodgers (Supervisor) & Phillip Millar (Supervisor)


  • Friction
  • Skid resistance
  • PFT
  • Road

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