\r\nThe decline was largely driven by a 61.2% year-on-year slump in coal traffic - until recently the largest commodity group - which dipped to 640 million net tonne-km. The decline is attributed primarily to a doubling of Britain's carbon tax, which came into effect on April 1 and was preceded by stockpiling of coal at power stations. Other factors influencing the decline include the switch to burning biomass, particularly at Britain's largest power station Drax, and the closure of Hatfield Colliery. The imminent closure of rail-served coal-fired power stations at Longannet in Scotland and Eggborough in northeast England do not auger well for the recovery of this sector.\r\nDomestic intermodal remained the largest commodity group, although volumes declined 1.4% to 1.59 billion net tonne-km, but there was strong growth in the second-largest sector construction, which increased by 7.1% to 1.04 billion tonne-km. International traffic through the Channel Tunnel also grew by 7% (albeit from a much lower base) to 160 million net tonne-km.\r\nMetals traffic declined by 9.1% year-on-year to 430 million net tonne-km while oil and petroleum fell 6.2% to 280 million net tonne-km. Infrastructure traffic, which is not included in the overall freight figures, reached 400 million net tonne-km.Freight train delays fell 19% compared with the first quarter of the previous financial year to 10.3 minutes per 100 train-km.