People are like drops of water. A large crowd often behaves like a river. It can move gently, or become turbulent, or become disastrously uncontrollable just like a flooding river breaking its bank.
I realised this when, in the late 1970s, I was researching the largest crowd in the world. This crowd gathers every March in Saudi Arabia to perform the hadj, the annual pilgrimage to Mecca. The hadj rites include walking seven times, anti-clockwise, around the cube-like structure of the Kaaba, and running seven times between the hills of Safa and Marwah.
Time-lapsed films of pilgrims around the Kaaba show them behaving like water coming out of a sink tap and swilling round the plughole. Most of the year, this flow is streamlined, what is called laminar flow - without fluctuation or turbulence. But during hadj, the situation changes drastically as more people try to enter the Sacred Mosque at the same time. When you open the tap to its fullest extent, more water enters the basin than can find its way out through the plughole.
In Mecca, this means that pilgrims are trampled, crushed or thrown against the walls. Outside Mecca, the crowd moves like a mighty river. And rivers don't like to be pushed through tunnels or forced to climb bridges - the kind of things that pilgrims have to do routinely when they move en masse to the nearby town of Muna. Disasters thus ensue with mundane frequency.
Now, it seems, the Saudis have finally realised that pilgrims behave like flowing water. So, wherever there is a danger of turbulent flow, mechanisms are introduced to transform it into laminar flow. Entry to the Sacred Mosque is cleverly regulated; the provision of more shade and resting places encourages pilgrims to slow down; tunnels have been abandoned in favour of huge walkways.
A crowd is a crowd. Its dynamics can be learned, scientifically. It took the administrators of the hadj 30 years to learn this science. Here, it seems that the organisers of the Dome remain resolutely unaware of these principles.
The flood of reports about queues at the Dome - even on dead days when less than 3,000 visitors bother to turn up - suggests that there is something profoundly wrong with its design. One can demonstrate this by using the fine art of "rough reckoning", the kind of elementary arithmetic that kids learn at secondary school.
The target, we're told, is ten million visitors a year. That's about 30,000 a day, and (with a 13-hour day to be introduced after April) just under 2,500 passing through the turnstile each hour (allowing for start-ups and shut-downs). Now, that comes to 40 a minute, but since we're talking orders of magnitude, let's say one per second. Let's further assume that nearly everyone who comes to the Dome wants to see the Body Zone, generally agreed to be the most ingenious and successful attraction. If everyone who entered the Dome rushed to the Body Zone, we would have a large turbulent crowd trying to pass through a small plughole. But that's the least of the problem. For streamline flow, we will have to get, on average, one visitor per second into the Body Zone.
The "capacity" of the Body Zone is not easily estimated, for it has all those stairs, curves and viewing places. But if people stay inside for 15 minutes (or a thousand seconds), then, at a rate of one person per second, the zone would have to cope with a thousand people at the same time. So let's be generous and make it a throughput of one per ten seconds. The travelator moves more slowly, and we can cut the number of people inside by ten. Let's have a hundred people each staying a thousand seconds. This is crowded, but still reasonably streamlined flow. Except that this rate, one per ten seconds (four thousand per day), gives us little more than a tenth of what is needed for the Dome to break even.
The numbers are rough; estimates may go up or down a bit. But the conclusion cannot be avoided: the Body Zone is a recipe for turbulent flow. Its throughput is far too low (by an order of magnitude) for it to be effective in helping the Dome reach its target. Simple crowd dynamics suggest that the Body Zone will always be plagued by queues. Indeed, the more people that visit the Dome, the longer the queues and the higher the proportion of people who simply won't be able to get in and will go away disappointed and angry.
When the round number of ten million visitors was invented, someone might have worked out the implications for the exhibitors. People are much more than ticket purchasing units. Bring a large number of people together, and they start flowing like water. Get the dynamics wrong, and you rightly get a flood tide of discontent.
