In no particular order:

The Wave

Lane Equilibrium

The wave has three components. These are both most applicable on the highway. The first is based on normal equilibrium theory. When in a traffic jam, as one lane starts moving, cars will switch into it, thereby stalling it and opening up another lane for movement. For optimum speed, one can ride these 'waves' and move through a traffic jam marginally faster. The trick is to know when to switch out of a moving lane and into a stalled one. However, switching lanes comes with its own cost, namely an increased risk of collision and the time cost of switching. Thus, 'surfing the waves' may provide a time benefit, but not reliably so and increase your risk of collision.

The Ratchet

This is closely related to the above point. Over a set period of time, two cars generally remain next to each other if they remain in their lane. Each lane may experience a wave which pushes it forward compared to the lane next to it, but once that wave dies and the next lane experiences a wave it will 'catch up' to the original lane. This is why when remaining in your lane, you will generally remain within the same bunch of cars (as long as they aren't switching). Thus, by riding a wave and then switching into the adjacent lane, one can 'ratchet' oneself through the jam (in comparison to their fellow travelers). This is really just another way of phrasing 'the wave'.

On/Off Ramp Effects

The second part of the wave is that the slow lane will be fastest moving lane before an off ramp and the slowest after. However, it is often not in your best interests to take advantage of this. First, because there is an increased risk of collision at an on ramp (as cars switch into your lane) and second, by just staying in the fast lane, one can often 'beat' someone employing this tactic. See short term vs. long term gain below.

Highway Clumping

The third part of the wave, is that when on a less crowded highway (not a jam), cars have a tendency to 'clump' together. I first noticed this because I drive slower than the average driver and often found myself in slumps where I was surrounded by very few cars, if any at all which alternated to clumps where there are many cars. I think these clumps form for two reasons. The first is that traffic lights generally force cars on suburban roads into clumps, and second because fast drivers usually have to slow down in a 'clump' and slow drivers are often pressured by the fast drivers to speed up, either by close following distance, or because they blindly follow the back of the car in front of them. Either way, it is always easiest to change lanes in a slump, and is especially useful if you are not in top driving capacity for some reason e.g. illness, glasses left at home, nervous etc.

Short vs Long Term Gain

The Traffic Light Effect

I've noticed a strange habit of drivers in Jozi, myself occasionally included: there is an obsession with short term traffic gains that lead one to think there is a net long term benefit. This mostly applies to non-highway driving.

For example, if three cars pull up to a light in the same lane, the second or third car will nearly always pull into the open lane. The most likely belief is that not having a car in front of you will allow you to floor it. This brings me to the next example, a majority of drivers, metro police included, break the speed. This majority increases the lower the speed limit i.e. more people break the speed limit when it is at 40km/h than when it is at 120km/h.

What I noticed in my driving, which as I mentioned earlier is generally slower than others, is that people who speed past me are generally waiting at the traffic light when I pull up. This is often true on the highway too, where I see someone who sped past me waiting at the light at the bottom of an off ramp. The traffic light is the important mechanism here, it makes all the silly short term gains people try and pull off quite silly. This leads to me to conclude that most people favour short term gains over long term ones. I am sure this is mostly non-rational and people aren't aware they are doing this, but it is interesting to watch nonetheless.

Consistency Is a Strategy

The wave theories I put forward at the beginning of this post may lead you to believe that the best tactic is to switch madly between lanes. I actually disagree. My tactic is to stick in one lane, generally the middle or fast lane (to avoid the on/off ramp effect). By knowing which lane to stick in, you can often end up beating people employing surfing tactics. A good example of this are taxis. By staying in the fast lane, I often 'beat' taxis who try and take advantage of the on/off ramp effect. I'm not sure if this is equally true for someone taking advantage of the wave effect, as most people ride the wave as it is dying. Many of the wave effects are short term gains which provide little long term benefit.

Right, that brings me to the end of my very unscientific, poorly structured traffic observations. I am very keen to hear other's experiences and advice though, please comment.