I'm going to let you in on a little secret:
It's 2019, and if he interests you, then you can ask him out. And you don't need to be 100% confident that he likes you in that way.
Next time you two are sitting in the car together, ask him if he wants to continue the conversation over coffee, on the weekend.
Assuming he says yes, go, and if you have a good time, tell him so. And then say, "Can we make it a real date next time?"
You already know that he's friendly with you. You don't need to see tea leaves or anything.
But if that makes you act, then consider this post to be your tea leaves.