I don't think there is a proper signal, but I used to signal my intention of continuous travel to oncoming traffic by pointing straight ahead. My city, in it's

I don't think there is a proper signal, but I used to signal my intention of continuous travel to oncoming traffic by pointing straight ahead. My city, in it's infinite wisdom, decided that bike traffic was supposed to go straight through an intersection while all motor vehicles had to turn onto the main street. The road markings were only for motor vehicles, while far less noticable road signs were for bikes. It got interesting at times, since some motorists assumed everyone had to turn. The city has since resolved that with a clearly marked bike lane. (Though it's fun watching vehicles as large as semi's try to fit into the bike lane, thinking it gives them the right to go straight through.)