'There are a number of towers in Dubai where not enough thought has been given to the lifts, and it makes the building very inefficient in terms of the time people have to wait,' says Josef Forkl, key account manager at the local office of Germany's ThyssenKrupp, one of the world's largest makers of elevators.

Louis Becker, design director at Danish architect Henning Larsen Tegnestue, agrees. 'Lift strategy becomes one of the key components of the whole design,' he says.

'The higher you go, the more people you need to move, and the more lift shafts are required. You need to have sky lobbies fed by express elevators, where people can then change lifts to move on to higher floors.'

The solution is to have more than one car in each lift shaft, either stacked on top of each other or with two independent cars, using software to regulate their movement.

The Burj Dubai, for example, will have 58 lifts, including two double-deck elevators to move tourists quickly up to the obser-vation deck.

Designers have also considered the problem of weight. The higher cars have to move, the more the cables weigh, so the machines pulling them have to be bigger and more inefficient.

'If you look at the floor plans of any big tower, you will see that the amount of space available to lease is very small compared with the amount taken up by elevator shafts,' says Becker.

'There is a huge cost implication, and the higher the building gets, the more it will cost developers to move people around.'