Evaluation of vehicle Speed Breaker Performance in Addis Ababa city
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Date
2020-12
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Addis Ababa University
Abstract
Speed breaker is a common name for a family of traffic calming devices that use vertical deflection to slow motor-vehicle traffic in order to improve safety condition. Speed-breakers are considered as “Sleeping Police Officer” and self-controlling which helps in containing over speeding also as called speed bumps, speed humps speed cushion and speed table.
Over speeding is one of the main causes for traffic crashes across the world. Pedestrians are one of vulnerable for traffic crashes due to over speeding. Thus to reduce this speed (i.e. beyond the speed limit) as a solution Addis Ababa Traffic Management Agency at selected place Constructed speed humps. Speed hump are the most common type of traffic calming measure across the world due to their low cost and easy for construction. It was not made study whether the Constructed speed hump reduce traffic crashes and Vehicle speed effectively before here in Addis Ababa. There for; this paper intends to evaluate the performance of vehicle speed hump in Addis Ababa. To achieve the objective of the research, the collection of primary and secondary data was conducted. Primary data: Field observations carried out to observe road geometrics and design characteristics of the road humps. And spot speed survey was conducted to collect Vehicle speed at different location around speed hump. The spot speed data collection was carried out during week day. All this data was taken from 10:00 am. to 12:00 pm. as to avoid peak hour for traffic flow. The weather during the collection was sunny. Secondary data considering traffic Crash data before and after speed hump construction from 2009 to 2012EC from the selected site sub city depending on the construction period of speed hump.
The finding indicates that the speed humps contribute to reduce the vehicle speed that is before speed hump for all selected site (36-38 Km/hr.) which reduced to on speed hump (17-19 Km/hr.). And it forces most of the driver to drive with in speed limit. The 85th percentile speed of the observed vehicles travel on speed hump on each site that is (21-24 Km/hr.) which is below the posted speed limit (i.e. 30km/hr and 50Km/hr.). The design characteristics of the road humps are also an important factor in reducing the speed of the vehicles all the selected area height with in 75mm to 100mm. In addition to this from the finding the percentage of traffic crash reduces after the construction of speed hump by (29% - 58%) in all selected site. The findings also showed a clear difference in the average speed of the vehicles before the speed hump and on the speed humps.
And also from t-test result for traffic crash data before and after speed hump construction for all selected site calculated t- Value > t- critical (t α (n-1)) so it shows differences in mean of traffic crash data before and after the construction of speed hump on all study area at 95% confidence interval. As a result, for drivers to acquire good driving behavior change the contribution of speed hump is high.
Concerning on geometric characteristic of speed hump depending on the posted speed limit the length of speed hump 5m ,7.4m and 10.8m, height (100mm) and shape (Modified circular) on all studied area.
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Keywords
speed hump, spot speed, traffic Crash