Investigating the effectiveness of speed hums and rumble strips as speed calming measures on roads in Kampala.

Abstract

In Kampala, Uganda, speeding is a critical road safety issue, contributing to 50% of road crashes, with motorcycles and light vehicles being the most affected. This study investigates the effectiveness of speed humps and rumble strips as speed calming measures on eight roads in Kampala, aiming to optimize their design to enhance road safety. Through meticulous field measurements, the research evaluated the geometric characteristics of these measures, including length, spacing, width, and height, and their impact on approach and traverse speeds for motorcycles and light vehicles. The findings revealed optimal design ranges, such as 60 – 70 metres for combination length, 40 – 60 metres for spacing, 35 – 45 cm for rumble strip width, 40 – 50 cm for rumble strip spacing, 5 – 7 metres for speed hump width, and 150 – 200 mm for speed hump height. These configurations achieved significant speed reductions, with light vehicles experiencing up to 52.55% reduction and motorcycles up to 31.88%. The study employed polynomial models to demonstrate non-linear relationships between geometric parameters and speed reduction, highlighting that light vehicles were more sensitive to these interventions than motorcycles, likely due to differences in vehicle dynamics. The research highlighted the need for standardization within the identified optimal ranges to ensure consistent efficacy across Kampala’s roads. Furthermore, it advocated for continuous monitoring to refine designs and address external factors, such as driver behavior and road conditions, which may influence outcomes. By providing evidence – based recommendations, this study contributes to Kampala’s Road Safety Strategy and aligns with global efforts under the United Nations’ Decade of Action for Road Safety (2021–2030) to halve traffic fatalities. The findings offer practical insights for policymakers and engineers to enhance the design and implementation of speed calming measures, ultimately fostering safer urban mobility in Kampala.