This review surveys the problem of surface contamination for cars, which poses a growing engineering challenge to vehicle manufacturers, operators and users. Both drivers’ vision and vehicle visibility need to be maintained under a wide range of environmental conditions. This requires managing the flow of surface water on wind screens and side glazing. The rate of deposition of solid contaminants on glazing, lights, license plates and external mirrors also needs to be minimised. Maintaining vehicle aesthetics and limiting the transfer of contaminants to the hands and clothes of users from soiled surfaces are also significant issues. Recently, keeping camera lenses clean has emerged as a key concern, as these systems transition from occasional manoeuvring aids to sensors for safety systems. The deposition of water and solid contaminants onto car surfaces is strongly influenced by unsteady vehicle aerodynamic effects. Airborne water droplets falling as rain or lifted as spray by tyres interact with wakes, vortices and shear flows and accumulate on vehicle surfaces as a consequence. The same aerodynamic effects also control the movement of surface water droplets, rivulets and films; hence, particular attention is paid to surface water management over the front side-glass and the deposition of contaminants on the rear surfaces. The test methods used in the automotive industry are reviewed, as are numerical simulation techniques
