Safety Performance of Speed Humps with Rumble Strips in Addis Ababa
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Date
2024-01
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Addis Ababa University
Abstract
With increasing urbanization, vehicle density on the roads has been increasing exponentially.
Most of the vehicles and roads are designed for a particular speed. The improved roadway
facilities have encouraged the drivers to drive fast in the urban roads. Excessive speed is a key
risk factor for road accidents and greater severity of the injuries in the event of an accident. In
such circumstances, it is very difficult to control a speeding vehicle unless some speed
management measures are provided. In our city Addis Ababa speed calming interventions are
implementing on the selected road segments of the city.
The primary aim of this study is to evaluate the safety performance of speed humps with rumble
strips in the context of Addis Ababa. To achieve this objective, two types of data were
employed: primary and secondary data. Secondary data was utilized to gain insights into the
characteristics of accidents on the specific road segments under study. In contrast, primary data
was speed survey data, road segment length data and frequency of speed hump (number of
speed hump and rumble strips) for the selected road segments. The speed survey data was
thoroughly collected using ERA pavement design manual Volume I, 2013 Vehicle
classification table. The Secondary data (accident data) covered the years 2014 to 2021 (2006
to 2013 E.C.) and was sourced from the Addis Ababa Police Commission and various sub-city
police departments.
The speed survey indicated that 85th percentile speeds were maintained below the speed limits
of 30km/h by a considerable percentage at different points along the road segments: 46% 20 m
before the speed hump, 92% at the speed hump, and 23% 20 m after the speed hump, across
the total selected road segments. The T-test results for Traffic speeds are statistically significant
for all variables and for all three pairs except Large Truck on before 20m of speed hump and
after 20m of speed hump pair.
Following the implementation of speed humps with rumble strips, the study shown a 31%
reduction in Total Equivalent Accidents (EANs), a 24% reduction in total pedestrian accidents,
a 54% reduction in pedestrian accidents involving crossing on the roadway, a 2% increase in
pedestrian accidents involving walking straight and a 35% reduction in accidents involving
public transport vehicles.Along with T-test results, it can be concluded that speed hump with rumble strips are effective
in reducing accidents. When we can see the impact of speed hump with rumble strips on
pedestrian safety the results also shows a significant change in the before-and-after study. With
respect to pedestrian accidents by main activity speed hump with rumble strips the result also
shows a significant change it can be concluded that speed hump with rumble strips are effective
in reducing accidents Pedestrians Crossing on Roadway. This affirms that speed hump with
rumble strips help in safe Crossing on Roadway. This means pedestrians can Cross relatively
easier and are safer than Crossing on the roadway without speed hump with rumble strips.
A T-test carried out on Pedestrians Accident Walking Strait in the before-and-after study
indicated no significant change. Using results of this T-test, we can conclude that, speed hump
with rumble strips, in this case, do not effect a significant change in reducing Pedestrians
crashes Walking Strait. A T-test carried out on public transport study indicated no significant
change. Using results of this T-test, we can conclude that, speed hump with rumble strips, in
this case, do not effect a significant change in reducing public transport crashes on the road.
Regression analysis used to produce the best relationship between density of speed hump and
85th Percentile Crossing speeds of the vehicles. Generally, the simple linear regression model
that include one independent variable (85th Percentile Crossing speed) .The signs of the
correlation coefficients in the regression model are as expected. The density of speed hump
shows a positive correlation with 85th Percentile Crossing speed.
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Keywords
Speed Humps, Rumble Strips, Safety Performance