A major problem is the age of railway networks, most of which are now more than a century old and suffer from historical deficiencies which are difficult to correct. For example, Britain's national network is carrying record numbers of passengers, but its restrictive loading gauge precludes the operation of double-deck passenger trains without huge investment to accommodate them. The small loading gauge even prevents the use of large freight wagons and deep-sea containers, although a lot has been done to accommodate hi-cube containers on major corridors serving the ports.

To make matters worse a lot of capacity was removed from the network during the second half of the last century in a vain attempt to make the railway profitable, and now some of this is being restored by reopening some lines, putting back track which was ripped up, and expanding stations. It is relatively easy to reduce capacity to cut costs in the short term but is far more expensive, very disruptive and time consuming to restore it. Unfortunately, this lesson still has to be learned in many countries.

London Underground (LU) also suffers from many small-bore tunnels and narrow station platforms and is desperately trying to boost capacity by installing communications-based train control (CBTC) to step up train frequency, buying higher-capacity trains, and removing bottlenecks. But it can be a frustrating business as Mr Mike Brown, LU's managing director, told delegates attending Global Transport Forum's recent CBTC conference in London. "We are carrying more than 4.8 million passengers a day, and we need to keep growing. But as soon as we do work on the network, that capacity is absorbed."

When building new railways or metros it is vital to choose the right system and provide sufficient capacity for future growth, as it is very expensive to return later to try to increase capacity. But political expediency can often take precedence over long-term needs.

São Paulo is a good example of this. The metro and commuter rail network is struggling to meet demand and large parts of the city are not served by rail at all, while São Paulo suffers from appalling congestion on its inadequate road network.

In a desperate attempt to provide more lines quickly and cheaply, São Paulo is building the first two of three planned monorails. While Bombardier has tried hard to produce a higher capacity monorail combined with CBTC, the vehicle on show at InnoTrans demonstrated that additional space is still required inside it to accommodate the very large wheelsets, a problem not faced with conventional rail vehicles. My fear is that in a large densely-populated city like São Paulo the new monorails will be quickly overwhelmed, which is why it is vital to choose the right-capacity system at the outset.

Failure to adapt to change, address problems head on, and take decisions in a timely fashion are major obstacles to long-term planning. Brazil's obscenely overmanned, un-commercial and underfunded railways were on the road to oblivion until privatisation in the 1990s saved them from extinction. But huge damage had been done by the time they were privatised, with deteriorating assets and virtual elimination of passenger services. Two decades later, while freight traffic has recovered and is rising steadily, a lot still needs to be done to improve track quality and services have been suspended on several lines either because of the poor state of the infrastructure or a failure to attract sufficient traffic.

Major new railways totalling 3883km are under construction in northern Brazil, but as we report this month, it is proving difficult to get the next new-line schemes off the ground. A lot of organisations are involved in the decision-making process making it convoluted and time consuming. A debate over how to operate the new lines is also muddying the waters. If the Ministry of Transport can achieve a breakthrough next year, and start construction of the first of the so-called PIL programme new lines, this could pave the way for more rail investment in Brazil.

As far as urban rail in Brazil is concerned, a lot of the projects which should have been completed in time for the Fifa World Cup last year never materialised due to political wrangling. This does not bode well for the future, where new railways are sorely needed in Brazil's major cities and plans are being drawn up to create a regional passenger network centred on São Paulo.

Railway projects need strong champions who will fight tooth and nail to make the right choices, get projects approved, and see them through to fruition. Railway infrastructure investment schemes are just too expensive to get them wrong.