Heavy traffic makes cycling safe, since cars can't move, How should a rider approach light traffic with fast moving cars???

First you need a mirror to understand dynamics from behind. I loved Mirrycle mirrors for twenty years, but other brand have caught up and have competitive products.

Second you need to be aware of your surroundings, look in front and try to understand drivers intention. Understsnd if they will be patient or aggresive. Keep in mind that most drivers are passive with bikes on the road. Understanding the environment will give you options if something goes wrong.

Third I like to weave in and out of the lane. When cars are far back I get into the lane to push them left. Once they get close I move to the right. The combination of them moving left and myself moving right creates a safe gap. I repeat this with each car during light traffic.

Please make sure you know your surroundings, and try weaving in and out to create larger safety gaps.