The years following the Wall Street Crash of 1929 until 1969 saw the creation of the Interstate Highway System, rapid growth of the suburbs and associated shopping malls, the growing importance of civil aviation, and growing dominance of the motorcar; it also witnessed the end of the streetcar system in the city followed by an increased use of buses and the creation of three successful trolleybus lines. The 1967 Detroit riot only accelerated the rate at which people, mainly white, were moving to the suburbs, with some 88,000 leaving in 1968 alone. The city population peaked at 1.85 million in 1950 before falling to 1.5 million in 1970; the metropolitan area's population peaked in 1970 at 4.5 million. There was growing opposition to urban freeway construction in many cities across the US, including Detroit, in the 1960s and the city authorities modified, scaled back and cancelled a number of schemes and passed a decree stating that no further urban freeways would be constructed in the city.