2/22/2016 TRB ROUNDABOUT COMMITTEE Roundabouts Are Not Always the Solution; Experiences in Nairobi, Kenya Colin Ridding Project Director Mott MacDonald Nairobi, Kenya 1
2/22/2016 Nairobi, Kenya • Second fastest growing city in Africa • Population of 3 million in Nairobi • Population of 7.5 million in Metropolitan Area • Expected to grow to 10 – 12 million by 2030 Nairobi, Kenya • Approximately 1.5 million passengers travel to the CBD daily (50% of City’s Population) • Approximately 47% of all commuters are pedestrians! 2
2/22/2016 Role in Kenya • November 2014 – June 2016 • EU funded Project • Traffic Engineering Capacity Building • Overseeing new Bus Rapid Transit System • Establishing New Transport Authority • Traffic Management Center • Addressing Congestion Problems! Congestion in Nairobi, Kenya • All routes into and out of town suffer with serious congestion • A 20 minute journey during off peak periods can be 2 hours plus during peak times • 6 lanes of traffic on a 3 lane highway! • Population rapidly increasing 3
2/22/2016 Congestion in Nairobi, Kenya • Driver behavior and Police Traffic Enforcement are major issues • Poor roads and lack of maintenance Congestion in Nairobi, Kenya Thousands of buses and matatus (minibuses), not very organized!! 4
2/22/2016 Congestion in Nairobi, Kenya • Many intersections are priority controlled or ‘4 way stops’ • Minimal number of signalized intersections • Several major roundabouts ALY10 General Principles of Roundabouts Principal objective is to • minimize delay for vehicles and to maintain a safe passage through intersection Most efficient when traffic • flows are balanced between the arms • Roundabouts designed to match traffic forecast demand 5
Slide 10 ALY10 Again - is this better near the beginning of the presentation? Albanese, Luke Y, 1/6/2016
2/22/2016 Advantages • Keep traffic moving with minimal delay • Aesthetically pleasing • Slower speeds • Fewer conflict points • Lower maintenance costs Roundabouts in Nairobi • Pressure from the media, drivers and previous studies to remove all roundabouts • Too dangerous for pedestrians and cyclists • Do not provide the expected capacity when compared to a signalized intersection • Poor driver behavior • Almost zero legal compliance • Role of the traffic police 6
2/22/2016 Roundabouts in Nairobi • Many roundabouts poorly designed • No road markings • No yield signs (not that anyone would yield!) Roundabouts in Nairobi • Higher speed road • No deflection • No Yield signs or markings 7
2/22/2016 Roundabouts in Nairobi Untitled.mp4 Decongestion Taskforce Committee • Ministry of Transport, other road authorities, Police and consultants • Set up to identify ‘quick-win’ schemes to reduce congestion in Nairobi 8
2/22/2016 Trial ‘Quick ‐ Win’ Scheme • At several roundabouts all right turning movements temporarily banned • Worked well at isolated roundabouts • Not so effective where other roundabouts in close proximity Typical Headlines Nairobi County Government • eliminates roundabouts Nairobi Major Roundabouts • To Be Blocked From Next Week Nairobi County Government • implements new traffic laws to eliminate roundabouts Nairobi County closes the 5 • Roundabouts on Uhuru Highway 9
2/22/2016 Trial ‘Quick ‐ Win’ Scheme • Long diversions • Increased congestion Trial ‘Quick ‐ Win’ Scheme Police Enforcement 10
2/22/2016 Trial ‘Quick ‐ Win’ Scheme Trial ‘Quick ‐ Win’ Scheme • Heavy Rain • Serious Flooding 11
2/22/2016 Flooding Flooding 12
2/22/2016 Flooding Outcome of ‘Quick-Win’ Scheme • Banning of right turns was not successful • Media and public pressure to remove the drums • Currently operating as roundabouts • Roundabouts will be removed and signalized intersections installed 13
2/22/2016 Roundabouts in Nairobi • Roundabouts not effective in Nairobi • Mainly due to poor driver behavior • Lack of Police enforcement • Lack of clear markings and signing Roundabouts in the UK • Numerous existing roundabouts have been converted to signalized roundabouts • Traffic signals can improve capacity at a roundabout • Signals regulate traffic flows 14
2/22/2016 Roundabouts in the UK • Can improve safety by managing high circulatory speeds • Easier to accommodate pedestrians and vulnerable road users Latest Innovation in the UK • Separates cyclists from other traffic • Segregated cycle lanes • First in London 15
2/22/2016 Latest Innovation in the UK • Cyclists have a poor safety record at roundabouts in the UK • More emphasis on safety • Many other cities implementing similar schemes Latest Innovation in the UK 16
2/22/2016 Latest Innovation in the UK Latest Innovation in the UK • Dutch style turbo roundabouts • Reduces speeds • Single circulating lane • Priority for cyclists at entry and exit lanes 17
2/22/2016 Summary • Roundabouts very successful in the UK, US and many countries throughout the world • Every intersection is different • All solutions should be considered Summary • Consider the needs of vulnerable road users • Roundabouts and signals do not always mix along the same corridor or within a congested urban area 18
2/22/2016 Summary • Safety record to be considered • Modeling should be undertaken Good Safety Record • Significant safety benefits demonstrated in the US • Converting signalized intersections to roundabouts in the US have reduced the number of crashes and injuries • A good safety record in the UK and elsewhere 19
2/22/2016 Thank You Further information; Colin Ridding +44 121 262 4372 Colin.Ridding@mottmac.com 20
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