Even with the anticipated reduction in background traffic, from the normal seasonal drop combined with the so-called 'Games-effect' -which sees fewer casual passengers travelling when they expect things to be busy - the arrival of so many millions of tourists will add up to a major safety and security challenge.
There has, of course, been considerable investment made in London's rail infrastructure to help meet these demands, both to facilitate access to the main Olympic Park and help visitors move to and from the city from around the UK.
In addition, the Olympic Delivery Authority (ODA) and Network Rail have plans to implement as many as 2,000 extra train services over the duration of the Games.
Also, many of venues being used are pre-existing, thus already set up to handle large scale events, with nearby stations and transport hubs well-versed in the necessary safety procedures.
However, the Olympic Games themselves are on a significantly larger scale, span a much more protracted period and will involve a quite different crowd dynamic.
The effect that thousands of people travelling in totally unfamiliar surroundings are likely to have on operations is something which has featured heavily in the planning.
An extensive security strategy has been developed to protect Olympic venues, events and infrastructure, including transport networks, as well as to prepare for events that may significantly disrupt safety and mitigate their impact.
From the British Transport Police (BTP) perspective, the operation revolves around a 64 day policing plan covering the Olympic and Paralympic Games and in preparation for that, several elements have been put in place.
"The threat assessment for the Olympics covers pretty much what you would expect: e-crime, fraud, terrorism, public order and crime," said BTP Assistant Chief Constable Steve Thomas - the Force's Gold commander for the Olympics and the joint Department for Transport / Home Office's national co-ordinator for cross modal transport security, covering rail, road, sea and air.
"From our planning perspective, disruption, from ordinary events such as a fatality on the line, from protest or public disorder, or a crime such as cable theft, are more likely to be a threat than terrorism," added Thomas.
The spectre of terrorism
Although much of the discussion of Olympic security in the media has tended to focus on headline-grabbing aspects, such as the deployment of ground-to-air missiles and RAF fighter aircraft to counter potential airborne threats, these more mundane events happen daily - and the statistics are surprising.
There were more than 2,770 cable related offences were recorded across the rail network in 2010 alone, and it is an alarming fact that while nationally the suicide rate is falling year on year, with the number of them that are rail-related remaining broadly static at around 200 per annum for the last decade, the relative proportion which take place at stations is increasing.
A further 100 or so - mostly youngsters playing on the line - are hit accidentally, bringing the total to around one a day.
ACC Thomas explained: "If you look at a threat matrix, a terrorist attack would be relatively low probability, but high impact, unless there is intelligence to change that."
Fortunately it seems there is little suggestion of specific targeting of the Games - at least for the moment, according to comments made by the Secretary General of Interpol, Ronald Noble, in a recently published interview in The Independent.
Nevertheless, with the Olympic Safety and Security Strategic Risk Assessment (OSSSRA) and Risk Mitigation Process summary document making the point that "as a high profile event, the Games are likely to present an appealing target to individuals or terrorist groups," the planning assumption is that the threat level will be at least 'severe'.
Stations on open rail networks obviously provide a much softer target for a conventional, one-off attack than air or maritime ports, and such isolated attacks are very difficult to stop.
However, security procedures such as station searches, CCTV, high visibility police patrols, stop and search, the use of behavioural assessment techniques and explosive-detecting dog teams do make for a very hostile environment that can deter, and at times, interdict the potential terrorist.
Unsurprisingly, these measures have been stepped up in the run up to 2012, and a range of enhanced procedures are being implemented to help minimise any potential disruption.
Tried and tested approach
"We have strengthened our explosives search dog capability," said Thomas, "and we will be having mutual aid officers from other forces assisting us during Games time. Related, but not specific to the Olympics, are the development of an armed officer capability and significant improvements to CCTV handling, including the creation of a London CCTV hub operation."
He explained that, although technology has its part to play, the Olympic strategy is specifically based on tried and tested technologies and systems, which includes briefing front-line station staff in particular during the run up to the Olympics on their role in keeping the network safe, spotting unusual or suspicious behaviour and dealing with incidents.
The importance of the joint role played by rail staff and management, transport police and the travelling public in helping maintain safety is something which Adrian Dwyer, British Transport Police's counter terrorism risk advisor, has alluded to previously, in the aftermath of the Moscow Metro bombings in March 2010.
Though it clearly cannot ever guarantee total security, it does provide a high degree of confidence, whether in respect of any potential terrorist threat, or routine - and statistically more likely - criminal activity.
Thieves and pickpockets
According to the Metropolitan Police, theft is the crime passengers are most likely to experience - despite the number of recorded instances on London's public transport network being at their lowest ever, with an average of just 11 reports for every million journeys.
Large crowds invariably attract the attentions of criminals, and thieves and pickpockets are expected to target the crowds arriving for the Olympics, in the same way they do for other big events like Wimbledon.
Vigilance, awareness and a positive approach to deterrence can prove as useful in combating common criminals as it is against terrorism.
Project Spiderweb, for instance - a joint collaboration between the BTP, the Metropolitan Police and Transport for London to reduce the instance of pickpocketing by 10% ahead of the Opening Ceremony - is just one of a number of initiatives being undertaken to keep the travelling public safe.
"On peak days during the Games," Thomas said, "there could be 12,000 police officers out - up to 1,000 on the rail system and it is that level of visibility, plus the participation of rail staff and whatever intelligence the security service and others have, that we are relying on."