How long would it take one million people to march to Uhuru Park, Nairobi?

 By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

15 June 2014

Anyone who has ever participated in the Nairobi marathon knows when the starting gun is sounded, it can take more than 20 minutes before the athletes at the end of the queue start running. The reason for this is that, as the start time approaches, all the runners tend to crowd tightly near the starting line.

When the race is started, only the runners at the front row have enough space to run, so they take-off immediately. They are then followed by those in the second row; then the third and so on. But things are not that orderly; there is a helter-skelter of overtaking and criss-crossing but gradually, running space is created for the athletes behind.

I tell this story to illustrate the fact that when people are moving – walking, jogging or running – they need more space than when they are standing stationary. Now last week, I wrote that the average person stands on a space of about 0.125 square metres. However, when a crowd is in motion, the space required increases dramatically.

By observing people walking in a crowded Nairobi street, I estimate that each person takes up about 1.5m back-to-front and 1m side-to-side. This comes to about 1.5 square metres – this is 12 times the 0.125sq-m required when the people are stationary.

Last week we found that, one million people would require about 4.5km of the 8-lane Uhuru Highway while standing. But when they start walking, the space requirement increases by a factor of 12; that is, 4.5 x 12 = 54km.

The only road in Kenya that can fit such a walking crowd is the new Thika Superhighway – the whole length of it from Thika to Nairobi! But of course this is not the only major inlet into the city; there are five others, namely, Waiyaki Way, Ngong, Langata, Mombasa and Jogoo roads. But all these are significantly narrower than the superhighway.

We may distribute the one million people equally amongst these six inlets giving each about 170,000 people. Obviously, the length of the queue will be longer in the narrower roads and shorter in the broader highways. So it will take longer for 170,000 people to pass through, say, Ngong road.

A walking crowd of 170,000 requires about 255,000 square meters of road. A two-lane road measures about 7m across, therefore, these people would stretch back for about 36km – from Uhuru park all the way to past Ngong town!

Now walking at about 5km/h, it would take the last person on this queue seven to eight hours to reach the city. This is approximately the time required to bring one million people to Nairobi in an organised, well-coordinated manner. However, political gatherings are anything but; so I’d not be surprised if it took three or four times longer. That is about 24 hours of continuous, non-stop walking.

Next time a politician imagines bringing one million people to Nairobi, he/she should think twice about it!