Development of Smartphone Accelerometer-Based Airfield Friction Assessment Tools

Abstract

Airfield managers have identified a need for contingency/emergency friction assessment tools that are both cost-effective and commonly found. Presently, airfield managers and pavement inspection teams prefer to measure friction at high speed with continuous friction measuring equipment (CFME) like the Findley Irvine GripTester. This device and the labor required to operate it are cost prohibitive. This paper explores an alternative, more economical measure of a surface’s frictional characteristics, that is, smartphone accelerometers. Accelerometers were standard friction assessment tools before CFMEs became available. Accelerometer-based friction testers measure the peak deceleration of a vehicle during braking. This acceleration, specifically the vehicle’s deceleration, is proportional to the surface’s friction coefficient. This paper covers research conducted to verify that smartphone accelerometers have sufficient accuracy and precision to operate as deceleration-based friction assessment tools. Findings reported here show that smartphone accelerometers, given sufficient conservatism, can function as deceleration-based friction assessment tools. Along with existing models, new regressions are presented that show correlation between smartphone deceleration measurements and high-speed GripTester measurements. The present work found that improved correlation was limited by common problems associated with poor reproducibility in braking tests.