John Massengale and Victor Dover talk about the design of protected bike lanes in the US vs those in Europe, in their excellent new book Street Design: The secret to great cities and towns:
In 2009 the city’s Transportation Department redesigned the section of Eighth Avenue in Manhattan shown in the above photo. In Manhattan, most public life takes place on the wide north-south avenues, but the design of Eighth Avenue gives most of the public realm to cars and throughput. The protected bike lane in the left side of the photo is sometimes referred to in America as a Copenhagen Lane; the street-level lane is sandwiched between the sidewalk and a buffer lane that runs along a row of parked cars. In Copenhagen, where 36 percent of the population commutes to work or school by bicycle every day, the form is better: the cycle track is raised above street level, with a curb separating it from the street. Below is a similar example from Amsterdam.
The track is usually attached to the sidewalk, which is often slightly higher still, so that there is another low curb between the bicycle space and the pedestrian space. Cars may or may not be parked next to the cycle track, depending on the width of the street.
When there are no parked cars, the cycle track provides a buffer between pedestrians and moving cars. Because the cycle track is attached to the sidewalk, the odd appearance of cars floating in the street is avoided, and the parking lane is not encumbered with the auto-scaled turn lanes, striping, and concrete pads.
I'm with John and Victor that the European examples are clearly superior in both function and aesthetics. I would only push back by saying that in the US we have soooo many streets and cities that desperately need some improvements and need them now. Some paint, cheap bollards and striping is an excellent first step to show success in places that are worried about the financial outlay of full improvements. Of course that doesn't excuse bad execution of those half-steps, but I'm firmly in the camp of stretching limited dollars for the most effect now. More lane-miles of protected bike lanes are needed in order to dramatically increase the number of people cycling. In time as transportation spending priorities shift we can then come back and make those first steps beautiful and permanent.