Traffic congestion on urban road networks has increased substantially across the world, since the 1950s. Traffic congestion on urban road networks has become increasingly problematic in major cities across the globe. In Zimbabwe, the number of vehicles is now estimated to be at least 1.5 million. There has been an unlimited increase in the existence of both vehicles and people especially in major cities of the country, particularly, Harare and Bulawayo.
Traffic congestion occurs when a volume of traffic generates demand for space greater than the available street capacity. As demand approaches the capacity of a road, extreme traffic congestion sets in. When vehicles are fully stopped for periods of time it leads to a traffic jam. When traffic demand is great enough that the interaction between vehicles slows the speed of the traffic stream, this results in some congestion. Congestion can also happen because of non-recurring highway incidents, such as a crash or roadworks, which may reduce the road’s capacity below normal levels. Congestion can also happen as a result of roadway obstruction, for example, in Harare city centre, at the intersection of Julius Nyerere way and Jason Moyo avenue, adjacent to the Joina City Centre; people (normally) waiting for Mushika-shika operators in the evening usually obstruct motorists proceeding towards Robert Mugabe way. Intermittently working or not working traffic lights also cause traffic congestion. In most instances, in Harare city centre, when it rains, there is a tendency to experience gridlocks (severe traffic congestion). This could be attributed to the fact that when it rains, roads get slippery, visibility is reduced and hence drivers have to drive slower and exercise extra caution. Unfortunately, some drivers switch to aggressive and selfish driving. During rush hours, traffic congestion is inevitable because of the benefits of having a relatively standard work day. In Zimbabwe, traffic congestion usually occurs in the morning between 7am and 9am as well as in the evening between 4pm and 7pm. During these times, roads leading to Harare’s city centre, for example, Chitungwiza road, Simon Mazorodze road, High Glen road, Mutare road as well as Arcturus road will normally be experiencing traffic congestion.
The fundamental law of traffic congestion argues that the number of Vehicle-Kilometers Traveled (VKT) increases in direct proportion to the available lane-kilometers of roadways. The implication is that building new roads and widening existing ones only results in additional traffic that continues to rise until peak congestion returns to the previous level. While congestion is a possibility for any mode of transportation, in this article we focus on automobile congestion on public roads. Causes of traffic congestion include obstacles in the road causing a blockage and merger. These can involve road works, road narrowing down, a crash, protests/demonstrations, malfunctioning traffic signals, aggressive driving and road closure for political, sporting or other activities.