I thought for sure they'd leave all of my most requested features on the cutting room floor, but they've got exactly the right brand of nerdy shenanigans in place. They actually model people's desire to travel by car based on parking availability! Perfect!
They did mention bike lanes in the last dev diary video as a customization option IIRC. So you have base roads and can dedicate lanes to bus/bike/tram if you want.
They have explicitly stated that bikes (and bike lanes) won't exist in the base game at release. It is a bit hidden, as they wrote that only on Twitter and in a comment under dev diary 1.