Architecture: A driverless train, a blighted destination: A railway deep into London's Docklands emphasises the potential yet to be realised in the east, says Gillian Widdicombe

Do you realise how vast is the desolate site served by the new extension to London's Docklands Light Railway, which opened on Monday? From Poplar to Beckton is eight kilometres (five miles); the Royal Docks alone are as long as the distance from Marble Arch to St Paul's. The London Docklands Development Corporation has been in charge of this, the largest redevelopment in Europe, for 13 years, yet only one new building catches your attention.

Like a pair of blue hatboxes with green knobs on, Richard Rogers's tidal pumping station nestles amorously next to Royal Victoria Station, helping to maintain the water level of the Royal Docks two feet above that of the Thames. Never mind that the splendid business and retail scheme which Rogers prepared for Stanhope on Royal Albert Dock was delayed by nit-picking and clobbered by the recession; at least the efforts of this little pimple may now be appreciated. With drains in, roads landscaped, trains working and the recession lifting, surely the developers will flood back in.

Maybe. Many things about Docklands in 1994 are more positive than for some years, and the bold silver structure of Ahrends Burton and Koralek's crane-like designs for the new stations announce a confident new beginning. But, for every step forward, Docklands still seems to take one step back. Climb aboard the new train at Poplar, and the 20-minute journey to Beckton will explain.

Please sit on the right - averting your gaze from the dreadful sight of the new Billingsgate market and its sprawling car-park - because the best views will be on this side. Don't worry that no one seems to be driving the train: the new Seltrac computerised system, visible as a blue cable between the rails, takes care of all that; in the event of failure, the train captain now meekly checking your ticket will leap forward and operate it under mobile-phone instruction.

The only snag about Seltrac is that it is not compatible with the old DLR track: upgrading the other tracks will necessitate closure from 9.30pm to 5.30am and throughout weekends until the end of the year.

Even then, transport problems will continue to blight the area, and passengers will be astonished to realise that neither the DLR nor the new Jubilee Line will stop at City Airport. Why? A tunnel under the dock was considered too expensive and safety regulations prevent it from going over the top.

Behind closed doors, Eric Sorensen, the LDDC's chief executive, is scratching his head about this conundrum; a loop to the airport alone may be too expensive, but a leg down to Greenwich and Lewisham would improve the railway's catchment.

Other unresolved proposals include the East London River Crossing, joining the north and south M25s, and a third tunnel at Blackwall.

As the train sweeps along the windy docks, bobbing up and down to vary the view, you pass the old Charrington coal depot. You can tell you're in Docklands: a hoarding suggests the site is for sale, though in fact it is not because it will accommodate the third Blackwall tunnel.

Conversely, the site of the demolished Brunswick power station seems to have been turned into a muddy golf range - you polish your stroke up from a private cubicle and a tractor collects the balls later - but later this year it will be marketed as a development parcel.

The LDDC spends too much time being afraid of its own shadow, say architects and developers; it's time to back some horses and stop asking too much for the sale of land. Invest in shops and entertainment, get some showhouses up.

They would say that, replies the LDDC, which has the Department of Environment on its back and must recoup the cost of drains, roads and trains.

Every now and then, a well- meaning soul such as Lord Palumbo talks of a new arts centre, or even a 23,000-seat arena, in the Royal Docks; and as you glide past the huge tobacco warehouse on the north side, known as Shed K, it's easy to imagine directors such as Peter Brook, Bill Bryden or Sam Mendes at home here. But without subsidy, such thoughts are pie in the sky. Hopes for an exhibition centre such as Birmingham's NEC may be unrealistic, too.

Today the site that seems most likely to be occupied first is the south side of Victoria Dock, where a lunch given by the Prince of Wales at Highgrove may lead to the birth of his latest pet concept, the urban village, in which you walk to work, shop conveniently and bring up your family in idyllic surroundings. Local residents are impressed, and the nearby Peabody estate has turned the first sod for new 'affordable' housing.

But cynics say the only thing new about the concept of an 'urban village' is Prince Charles's enthusiasm, which sheds little light on old problems of marrying good design to profitable building. Another 1,500 homes in which you can't open the fridge and the oven at the same time? And who will want to live near the end of the flight path to City Airport?

The DLR sneaks north, to the site of the former gas works now euphemistically called Gallions Reach. The ghostly cluster of burnt-out buildings look familiar to those who have seen Full Metal Jacket.

This is a historic British Gas site: a century ago the largest gas works in Europe, sitting on marshland and often enveloped by its own private fog. Today only a few yellow gasholders and a skein of silver pipes supplying North Sea gas remain, but the land is contaminated by methane, and expensive to reclaim. Residents in Newham's nearby Windsor Park estate already fear that gardening activity and land drainage may be making their land unsafe again.

The LDDC seems to realise that some of its eyesores will take years to resolve. Worst of all is the Purafoods factory that crowns the mouth of the river Lea with a humiliating jumble of pipes and oil cans. Purafoods employs a substantial number of the 900 residents in this area, so no one would dare talk of relocation or closing down; perhaps an EC grant, for upgrading the factory to meet more stringent food regulations, will eventually provide a more appropriate cladding.

Look down instead, as the train slides towards the Lea peninsula, and you will see that the LDDC has gone green. Here a substantial ecological project features the recreation of a floodwater pond. Species identified last year included bishopsweed, silky bent, Austrian camomile, Sumatran fleabane and American willowherb, all apparently self- seeded from cargo boats docking from South America and Indonesia. Butterflies are ordinary so far, but birds expected include crested grebe, mute swans, tufted ducks and various terns and shags.

Not all green schemes have such a happy outcome: a proposal for a saltmarsh ditch in Beckton stuck in the mud when local residents realised that a virulent form of mosquito would be the first to colonise it.

Admirable though this wildlife programme is, I can't help remembering the French diplomat who explained how his country managed to build its grands projets. 'In France,' he said, 'when we drain the swamp we do not consult the frogs.' In Docklands, however, we not only consult frogs, but also build homes for them.

Wildlife may give the LDDC a better conscience, and improve relationships with local people; but it is the course of least action, least money, and doesn't need a Seltrac rail system.

The LDDC has only three years to run before it must give the dramatic waterscape of the Royal Docks back to Newham, whose priorities would favour better housing rather than bold visions. Will the LDDC settle for a gradual decline, or panic and dispose of small parcels of land to ensure some hectic activity before the millennium?

(Photograph omitted)