Impact of Sinusoidal Speed Humps on the Dynamics and Comfort of Electric-Assisted Child-Carrying Bicycles

Abstract

The rapid growth of electric-assisted child-carrying bicycles in urban areas marks the need to evaluate passenger comfort when traversing traffic-calming devices. This study compares vibration exposure on sinusoidal speed humps and conventional speed bumps in Japanese Zone 30+ areas. A controlled experiment used triaxial accelerometers at three bicycle locations (front child seat, frame center, rear child seat) across 144 scenarios combining two-wheel sizes (20-inch, 26-inch), three loading conditions (unladen, 12 kg front load, 12 kg rear load), and four speeds (5 to 20 km/h). Acceleration signals sampled at 50-millisecond intervals were analyzed using the Dynamic Comfort Index (DCI) and ISO 2631-1 metrics: Root Mean Square acceleration (RMS), Vibration Dose Value (VDV), and crest factor. Sinusoidal profiles produced DCI distributions closely aligned with smooth-road benchmarks within 5% of baseline comfort whereas conventional bumps produced DCI values deviating up to 25%. Results show that sinusoidal humps significantly reduce peak and cumulative vibration across all configurations, with the greatest improvement at the front child seat. Sinusoidal hump profiles obtained comfort levels within acceptable thresholds even at higher speeds typical of electric assist, whereas conventional bumps often exceeded discomfort limits. These findings support adopting sinusoidal speed humps in school zones to balance effective speed control with child passenger comfort and safety in sustainable transportation systems.