You gain nothing by driving fast

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

21 March 2021

The greatest factor that determines how fast a car can move is not its power nor is it the skill of the driver! It is the number of other cars on the road. The second greatest factor is the speed of the other cars.

On a deserted road, the power of the engine and the skill of the driver are the only limiting factors. When other cars are present, they obstruct the motion and the vehicle must slow down to a level close to the ambient speed.

On a good day, the journey from my house to Thika town – a distance of 45km – takes me about 50 minutes. This works out to an average speed of 54km/h. But, for most of the trip, I am usually driving at about 100km/h.

So where does the 46km/h disappear? Well, a lot of the time is spent in the short 3km distance from my house to the superhighway and the final 3km from the highway to Thika town centre.

These two sections of the journey have heavy traffic and they take about 10 minutes each. That is, a total of 20 minutes out of the 50! This works to just 18km/h.

If we remove these slow sections out of the measurement, we are left with a distance of 39km which is covered in 30 minutes. Thus, my average speed on the highway is about 78km/h.

The difference is accounted for by presence of other slower vehicles [large and small goods vehicles] and permanent obstacles in the form of speed bumps (who puts speed bumps on a highway?).

I have noted that, if I increase my peak speed on the highway does not save much time. If I aim to drive at, say, 120km/h, the time saved is insignificantly small; it is far less than 5 minutes.

Now, since the regular clockface is subdivided in five-minute intervals, we have become accustomed to ignore duration less than that in normal usage. Thus, for me, it doesn’t make any sense to drive faster than 100km/h on the Thika superhighway.

What if the distance was much longer, say, 450km instead of 45km? Well, in that case one might take 6 hours when driving at a peak of 100km/h and, perhaps 5h:45min is the top speed in increased to 120km/h.

I must emphasise: these are peak speeds, not average speeds. So, do NOT write to point out that 450 divided by 100 is 4.5 hours! So, is the 15 minutes gained in a 6-hour journey worth it?