From China to Europe, trillions are being pumped into high speed rail networks. But as squeezing more speed out of them becomes harder, it's looking like high speed rail isn't the solution to our transport dilemma.

On April 3, 2007, a sleek train raced across the countryside of northeast France, pursued by a small jet aircraft. On an open stretch of track between Prény and Bezannes, the train galloped ahead – eventually reaching 500kph. Officially, no train operated by TGV, the French state-owned high speed service, had ever ever surpassed 515kph, the speed record set by the same firm 17 years earlier. This attempt, christened Operation TGV 150, was aiming to reach 150 metres per second, or 540kph. As the chase aircraft beamed data and video to pensive engineers, the train pushed beyond 540kph, before setting a new world speed record: 574.8kph.