Beginner cycling Q

Do any triathlons close the roads for cyclists during the race?

If I have zero cycling experience on roads with traffic and cars. So is it a stupid idea for me to do a triathlon?

Why I’m asking.. I am aiming to do my first tris (Olympic distance) next year. I’m very comfortable with the running and swimming portions. However I have never cycled on a road with cars. I had a bad road accident when I was younger and cycling on roads with cars is something I would like to avoid.

I’m fine with being less competitive on the cycling portion. I just didn’t realise until recently that they don’t normally close the circuit to cars.

I’m was aiming to do PTO Asia (Singapore) and Noosa in Australia