“A developed country is not a place where the poor have cars. It’s where the rich use public transportation” – Gustavo Petro, Mayor of Bogota. With the growing middle class in Rwanda, the reverse can be said to be true; the roads are crawling with automobiles. The nightmare of driving during peak hours tends to visit me even in my sleep, especially the long ‘funeral procession’ wait in traffic. Nowhere do I feel such strong sentiments as at the ubiquitous roundabouts around the city! Having griped and whined for months, I decided to acquire an empirical understanding of these structures. I am no transportation engineer so I did a bunch of reading on the subject and found an interesting analysis on roundabouts by the Mathematics department at the University of Washington. Describing the model of roundabout traffic flow as a non-linear first order partial differential equation relating speed, traffic density and traffic flow, they were able to evaluate a number of aspects related to roundabouts. The study concluded that increasing the number of lanes increases throughput (how many cars make it past the intersection) especially for heavy traffic and that increasing the radius of roundabouts decreases delay for those entering below 20m/s but increases delay for vehicles entering above 20m/s. The boring mathematical details aside, a clear demonstration is the main roundabout in Kicukiro versus the roundabout at ‘Ku Mazi’ on the way to Rugunga. Given the heavy influx of vehicles from three directions at the small Kicukiro roundabout, queue development causes long lines at entry points (cars are at minimal speed); this is unlike the Rugunga roundabout that sees light influx of cars and therefore does not create traffic jam. Using the logic of the study above, a larger radius may address the problem in Kicukiro. However, digging deeper into the matter, maybe we don’t even need this mathematics to address part of the problem. Going back to the two-lane Kicukiro roundabout: since both lanes have the option of continuing through or turning right at a feed-out lane, the confusion created by users in the inner lane turning right while users in outer lane continue through wastes time and increases the wait. It doesn’t help that many drivers don’t adhere to the ‘give way before entry’ principle on which roundabouts are designed.Now that I am done venting, it so happens that roundabouts are not only safer than regular intersections but are actually more fuel efficient than stopping at traffic lights (30 per cent less fuel). Even though roundabouts present opportunities for fender benders, they eliminate the dangerous ‘T-bone’ car wrecks common at traffic light intersections. Next time you feel the urge to complain, remember that it is your responsibility as the driver to make a difference. Drive safe this week!Fact of the day: One fifth of the world’s road deaths occur in Africa even if the continent boasts of 2 per cent of the world’s registered vehicles. Road traffic injuries are the 4th leading cause of death in people aged 15-44 years, and the second leading cause of premature death for young men, after HIV/AIDS.
