Portland is also one of the most Bike friendly cities in the US with about 3% commuting by bike. This painting does not interfere with bikes. The thermoplastic that they make crosswalks out of does have slick surfaces.

This painting does not interfere with bikes. The thermoplastic [..]

What happens when this plastic surface is wet?

Re" what happens when the plastic surface gets wet".
In 1972 I experienced this on my moped in Copenhagen. The moped slipped on a painted stripe and I went down in front of a bus. Luckily the bus managed to stop.
In Modern Copenhagen, Bikes and cars are seperated. You can study the standard construction modes in Copenhagen from the "vejdirektoratet" in this link- http://www.vejregler.dk/pls/vrdad/vr_layout.vis?p_gren_id=2707
Danish- but well illustrated with many Pictures.
kind regards/And1

Thanks And1 - unfortunately my Danish isn't good enough to understand all items on that picture. As a cyclist I really shun all wet plastic surfaces. They are like wet leaves in the autumn - can give you are terrible slip, especially in turns.