 Complete the following phrase:  By 1985, Detroit was the sole American venue on the F1 calendar - Las Vegas had been dropped after 1982, Long Beach switched to Champ Car for 1984, and a new event in Dallas only lasted one year after the heat and deteriorating track conditions almost saw it cancelled on the morning of the race. That year saw Ayrton Senna take pole position, and he went on to enjoy substantial success at the circuit, winning the 1986, 1987, and 