Transport for London can only see one thing in their crystal ball: traffic, and more of it. In their car-centric world view, the only way of getting something done is to get in a motor vehicle. The predicted growth of London population will inevitably mean more traffic, the alternative being economic stagnation and ruin. Right?
Predicting the future is very difficult to do, and no-one really wants to try because they look ridiculous if they get it wrong. However, if we're going to plan for the future then we have to try to predict it. The intelligent thing to do is to look at the various factors that will interact, and come up with some likely-looking scenarios. The problem with this is it can turn up some surprising, and frightening predictions. Like climate change for instance. No politician, or transport engineer, wants to be delivering a message people don't want to hear. So the lazy, cowardly way to predict the future is to forecast that it will be exactly like the past, only more so, in a nice, gentle, linear-progression kind of way. People can relate to that; they can understand it and it doesn't frighten or threaten them. Even if it's unlikely to be true. That's why we get TfL predicting more traffic, even though climate change, increasing oil prices and squeezed incomes all point in the other direction. There's also another factor that may driver traffic and indeed travel in general down: technology.
Communications technologies mean we can keep in touch, work and shop remotely. That's one reason why high street shops are closing. These days, you could live a fairly rich life without ever setting foot outside your house. Technology, used correctly, can enable fewer motor journeys to be made.
The building blocks of technology that allows you to hail cabs electronically has been around for a while - smartphones with geo-location - and now we're starting to see apps that make the concept a reality. Basically, you signal your position and intended journey to a 'market', and a nearby cab driver can accept your fare, drive to your location and pick you up. In the long term this should mean less downtime for cab drivers, as there will be fewer cabs driving around empty looking for a fare and hence less congestion. It also means that if there are no cabs nearby available to take your fare, you could take the bus or tube instead of standing by a kerb waving haplessly at a succession of occupied black cabs. (However it's not all great news for black cab drivers because there is no reason why minicabs cannot apply for hire electronically, removing the one key advantage the black cabs have over their private-hire rivals.)
Technology will in time make it easier for people to take public transport or walk. Smartphones will become ubiquitous very soon indeed - even my wife has a smart-ish phone, and she's usually the last person in the country to embrace new technology - and all-you-can eat tariffs mean users don't have to worry about using apps such as Google Maps to find their way around. There will also be apps that know your current location and help you choose the fastest, or easiest, or cheapest way from A to B, and tell you when the next bus or train is due. So this should help reduce the number of people who only take a cab because they don't have the information to choose another mode. Technology may also help people avoid travel, by finding restaurants or entertainment close by.
Logistics is another area in which technology can reduce journeys. Currently, there are a lot of half-empty vans being driven around London. With real-time location information and the ability to match a load and its destination to a nearby vehicle, it becomes possible to deliver goods in a short timescale in a cheap and efficient way, with far fewer vehicles on aggregate than we currently have.
Above are just a few concepts that can be implemented with currently-available technology. You won't see much discussion in TfL documents about how these easily-foreseeable developments will affect traffic levels, yet they are trying to predict traffic 20 years into the future. 20 years ago, the internet didn't exist for practical purposes. TfL are not so much looking at the world through a car windscreen as through the rear-view mirror.