Alistair Darling's father was a civil engineer on one of London's most controversial roads - the Chiswick flyover, which was among a handful of urban motorways that triggered a storm of protest in the 1960s and 70s.

Offering a rare snippet of personal information, the transport secretary revealed that Sandy Darling, who has since died, helped build the elevated section of the M4, from 1962-65. The Darling family keeps a photograph taken shortly after the section opened, showing "maybe 50 cars" - a fraction of the number now using the road daily.

Together with the A40 Westway, built a few years later, the road triggered protests under the slogan "homes before roads". Residents hated the noise, pollution and unsightliness.

One transport expert yesterday described the flyover as a relic of a discredited policy: "If you don't worry about the environment, it's a great example of how to take through traffic from an area and dump it in a sewer in the sky."

Designed by Sir Alexander Gibb and built at a cost of £5m, the road was recently refurbished by the highways agency after the discovery that de-icing salt had corroded metal bars inside its concrete pillars.

Hugh Collis, a transport author, said it was a symbol of the failure of "predict and provide" road building: "It was one of the first and last of its type in the capital."