Two more train derailments, in Northampton and Bristol, and Connex South delays caused by leaves on tracks spelt another day of misery for rail travellers in Britain yesterday, as problems spread to the roads amid reports that demand for domestic flights are up by 30 per cent.A motorway pile-up on the M4 at Wiltshire added to the sense of gridlock, while thousands of passengers faced delays on services from Kent and Sussex as Connex conceded there were far too many cancellations to list individual train times.Railtrack warned that services in and out of Southampton would not return to normal for a fortnight after the 1.30 am derailment of two wagons of a 27 wagon freight train. Local operator Silverlink later put on buses to take passengers to Milton Keynes but admitted it did not have enough buses to cope with the rush-hour demand. While Railtrack said flooding appeared the likely cause of the Northampton incident, freight company EWS said the 2.30 derailment near Bristol- involving a locomotive and three empty coal wagons - appeared to have happened after the driver passed through a red light. The Bristol derailment caused pollution along two miles of wetlands, putting local wildlife in danger. A number of swans, cygnets and ducks taken from a nearby river, were found to be contaminated with red diesel oil. The RSPCA said it was hopeful the would make a full recovery.The BBC last night confirmed a build-up in road traffic as a result of the continuing rail problems, with the AA warning drivers to allow 5 hours for a car journey from London to Manchester. A similar journey by train was reported to last four hours, with delays to be expected, at a cost of £150 sterling for a return ticket with no guarantee of a seat. In the house of Commons the Prime Minster rejected suggestions by the Liberal Democrat leader that John Prescott's present Environment, Transport and Regions brief was too big and tat a specific Transport Secretary be appointed. Mr Blair insisted it was "necessary to inject some common sense" into the rail system, which was suffering form years of under-investment.However, Mr Vernon Hince said " Now is the time for the Government to act by taking control of the situation".