The result of this economic activity was the rapid growth of the population of Perth, and a marked change in its urban design. During the 1950s Perth actively began to develop along the lines dictated by the rise of the automobile and the suburban sprawl, a development acknowledged by in the Hepburn Report (1957), which noted that Perth was beginning to resemble a pattern of development less in line with the British experience and more in line with North America. This was encouraged by the opening of the Narrows Bridge and the gradual closure of the Perth-Fremantle Tramways. The mining-pastoral boom of the 1960s only accelerated the pace of urban growth in Perth. By 1975 the population of Perth has risen to 825,000.