One of the problems (or opportunities, depending which side of the fence you're on), is that by definition 'intermodal' traffic is very easy to switch between transport modes, so it's very sensitive to transportation price and service quality.
The short distances from ports to customers here (a lot of the UK is within a days' drive of any major port) makes rail very vulnerable to truck competition, so it's hardly surprising that train services to ports come and go.
(Even in the US, where the two major 'western' railroads carry the largest share of the west coast - midwest/east coast 'land bridge' container traffic, they are looking over their shoulders at what effect the newly enlarged Panama Canal might have on that huge business for them - and of course the east coast ports are rubbing their hands at the prospect of more/larger ships calling....)
The other problem is the way the shipping lines operate. By the end of this year most of the major lines will be members of groupings allowing them, subject to global approval by respective governments to share space on each others sailings. This will mean that Maersk, CMA-CGM and MSC will become members of P3, Hapag Lloyd, OOCL, NYK, APL, MOL, Hyundai will be G6, whilst Hanjin, Cosco, K-Line, Yang Ming, and Evergreen will form CHYK. These groupings will mainly dictate east/west services around the globe, whilst only some north/south trades will be covered. These groupings probably represent about 90% of deep sea traffic in the trade lanes covered. Because historically shipping lines have favoured individual port calls, ie Maersk prefers Rotterdam, whilst MSC prefers Antwerp, whilst CMA-CGM favours Le Havre, the lines used different terminals in these ports and have to decide which terminal to concentrate their services on, in order to gain the economies of scale. In the UK there is no choice at individual ports, so what tends to happen is the lines switch between ports. Maersk and MSC both favour Felixstowe, but CMA- CGM prefers Southampton, but MSC and CMA-CGM also favour feeding cargo to regional ports, in fact the MSC service into Liverpool has one of the largest container exchanges in the network for a feeder service. Maersk on the other hand prefers a single port policy, although it has recently been using a feeder service into Liverpool for some specific traffic. P6 favour Southampton, but Hapag Lloyd runs services out of London Gateway, instead of Tilbury, Liverpool, and slot charters on MSC services out of Felixstowe to South Africa. As these groupings get larger, the effect on the ports is greater, and can have extreme changes in fortune, Thamesport being the classic example, next could be Tilbury because it is not able to handle vessels of 5000 teu or more which are set to become the norm in many deep sea trades.
The USA has it's own problems, with no ports in the country able to handle a 18000 teu vessel and out-dated working restrictions, as well as infrastructure that is incapable of handling containers with a payload of about 18000 tonnes. US law prohibits foreign liner companies being involved in US coastal trades, and the requirement to operate these ships under the US flags means feedering containers, European and Asian style is not an option.
