The Portuguese Grand Prix returned to the calendar in 1984 to the Autódromo do Estoril in 1984. After the deaths of Ayrton Senna and Roland Ratzenberger at Imola in 1994, the Estoril track was changed. A new chicane was built in place of the tank curve, as a safety measure. But Estoril was considered an unsafe and outdated track. The last Portuguese Grand Prix was in Estoril on 22 September 1996.