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 . After the deaths of Senna and Roland Ratzenberger in Imola in 1994 , the Estoril track was changed , with a new chicane built in place of the tank curve , as a security measure .