Citywide Road Safety Impacts of Speed Humps in Addis Ababa

Abstract

In Addis Ababa, Ethiopia, pedestrians account for more than 80 percent of all fatal crashes. Speed humps have been implemented citywide since the launch of a road safety strategy in 2017 to calm vehicular traffic and improve road safety. The city targeted major roads and installed over 550 round-top asphalt concrete speed humps with a height of 10 cm and lengths greater than or equal to 4.9 m. This study assessed the impact of this citywide intervention in terms of crash reduction. A before-after design was used, analysing geospatial data on speed humps and fatal crashes for three years before and after implementation. A 250 m buffer is created around the speed humps using QGIS to represent their influence areas. The Join attributes by location (summary) tool was used to count the total number of crashes within these buffer areas. Fatal crashes decreased by 26 percent within the speed hump influence areas, while they increased by 13 percent outside the areas. The installation of speed humps was estimated to have prevented 135 fatal crashes over three years, corresponding to approximately 142 lives saved. Further analysis assessed the relative change and its significance showing a 35 percent reduction in fatal crashes in speed hump influence areas compared to outside the areas using the Tanner test (k = 0.65). The chi-squared test indicated that the difference was statistically significant (at a 95% confidence level). Given the limited availability of alternative interventions, it is reasonable for cities in low- and middle-income countries to continue installing speed humps alongside complementary measures such as traffic signals and speed management technologies. This aligns with the principle that human life should not be compromised for mobility.