Spray from commercial vehicles: A method of evaluation and results from road tests

Abstract

An accurate and repeatable measurement of truck-induced spray is required to develop and test spray-reducing devices. Such a system is described, based on a sequence of CCD-captured video images of a black and white chequerboard which was partially obscured by spray from a passing test truck. Images were analyzed to reveal the contrast changes, from which spray densities were inferred. Results of on-road trials are described and it was found that none of the tested wheel-mounted systems offered any statistically significant reduction in spray. Supporting track and wind-tunnel tests documented the flow vectors close to the truck; for an unmodified vehicle and when fitted with sideskirts and a cab-mounted add-on aerodynamic device. It was concluded from the flow field studies that the problem of vision impairment for a passing motorist would be significantly reduced when sideskirts and (for vehicles hauling a high load) correctly-matched cab roof deflectors were fitted. This offers the trucking industry the combined advantages of drag and spray reduction. © 2009 Springer-Verlag Berlin Heidelberg.