Thesis Open Access

Turbo Roundabout as an Alternative of conventional Roundabou : Case study at Africa union Intersection

Mahlet Yegizaw

Thesis supervisor(s)

Melaku Sisay ( PhD )

Addis Ababa is experiencing rapid growth in the business and construction activities
which in turn increase the number of vehicles with an alarming rate. For this reason,
currently there is an attempt to develop infrastructures like road networks improvement and
evaluation and improving intersection control mechanism in the city. But still there is a
huge gap in developing road segment and intersection with good operational and safety
performance. The introduction of the turbo roundabout in Addis Ababa can have a
massive impact on the road safety and capacity problem in the city.
In this study the roundabout at Africa Union intersection was modeled using VISSM
software and proposed and designed Turbo roundabout using Torus software as an
alternative solution in terms of operational and safety performance.
Traffic volume is a major input, motorized Traffic data was collected in morning and
night time peak hour for 2 consecutive days from 8:00am to 9:00 am in the morning
and from 5:30pm to 6:30pm for night peak hour. The hourly traffic volume distribution
revealed that the peak hour traffic between 8:00am to 9:00 am in the morning.
Pedestrian volume count was used from secondary data of previous study on each
approach that cross the road on both directions in-bound and out-bound to the approach.
Then both existing and proposed intersection operational performance analysis is
conducted using VISSIM software.
The results showed 85sec delay and 80m queue lengths with F LOS. As an alternative
solution reconstruction of the intersections has been made into Rotor turbo roundabouts
and results revealed the intersection better performance with 32 sec delay, 34m queue
length with D LOS. Finally, the performances for two types of roundabouts are
determined with the using VISSIM software.
The analysis has proven that with the input parameters, rotor turbo roundabout offers
better performances and safety improvement compared to the existing intersections as
it can be taken as an alternative solution.

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