The Dutch know how to build bike infrastructure like nobody else. Their network of bikeways is made up of 3 main street typologies. One is quiet, low-speed (<20mph) residential streets that offer through access to bikes and pedestrians, but not to cars (known as bike boulevards or neighborhood greenways in the US). The second is physically separated bike lanes that parallel higher speed motorized thoroughfares, and have priority at intersections. The third is fully separated bike paths, which are not shared with pedestrians or strollers or pogostick riders, and which are wide enough for two riders side-by-side in each direction. Getting this stuff built in the US is a political issue, not a technical one.
Even just barely physically separated bike lanes command much more deference from motorists than paint on the ground. Would-be urban cyclists consistently (and Boulder is no exception here) cite fear of traffic and the desire for separated infrastructure as the number one reason they don’t bike at all, or don’t bike more. And it doesn’t have to be a big infrastructure investment — even just red plastic cups taped to the edge of the bike lane will keep cars at bay!