The traffic flow issue is quite complicated.
Around 2003/2004 I was involved in a project to install and program the traffic lights at one of the roundabouts in the city. When we asked for vehicle density data, we were given figures from 1986! Over twenty years old.
We did a quick impromptu survey and programmed the controller. Then we needed to test run the system for two weeks in order to see where to fine-tune the timings. This became almost impossible because the cops would never allow the lights to control the flow - interfering all the time.
At one point a cop asked why we were wasting money with extra lights inside the roundabout. His face lit up when I explained to him that they were necessary to create time for pedestrians to cross an "exit". "Oh; Kumbe? Unajua sisi hatufundishwi chochote kuhusu control. Kila mtu hufanya kivyake"
A few years later I met the then city traffic engineer and asked him what was his biggest challenge. "Political interference" he replied.
Politicians order the cops to stop the traffic and clear the way for them. This causes major traffic jams all over the city. The biggest culprit is the VP! This is how you find yourself stopped for 45 minutes at the Lusaka/Mombasa road roundabout waiting for nothing!
Nothing is real unless it can be named; nothing has value unless it can be sold; money is worthless unless you spend it.