Validation of an Outdoor Coast-Down Test to Measure Bicycle Resistance Parameters

Abstract

Bicyclist rolling and aerodynamic resistance parameters are needed to estimate speed and energy expenditure in various travel analysis applications. These parameters have been investigated for sport and professional bicyclists, but better understanding is needed for real-world urban bicyclists. This paper describes a field coast-down test to measure bicycle resistance parameters that can be administered during traveler intercept surveys and generate representative data for advanced bicycle travel models. Mathematical models are developed that expand on past methods by accounting for varying wind and grade and allowing for increased measurement locations per test. A 12-sensor, 1-m test setup is developed, and indoor and outdoor validation tests are performed. The additional measurement locations yield higher precision than the previous three-sensor methods, but as expected, the precision of outdoor tests is lower due to inconsistent wind, grade, and riding surface. Outdoor validation tests generate rolling resistance coefficient estimates of .64±.13 and effective frontal area estimates of .63±.11 m2. Outdoor tests in a headwind are sufficiently sensitive to identify significant changes in resistance with riding position and tire pressure and are expected to generate realistic parameter estimates for parsimonious modeling of on-road bicyclists.