You'll know, because your car will know, because that other car will have whispered something in his ear, like, "By the way, five minutes, motorcyclist, watch out."
Vão saber, porque o vosso carro  vai saber, porque o outro carro terá dito algo ao seu ouvido, tipo: "Já agora, daqui a 5 minutos, "motociclista, cuidado."