Bike lanes serve many functions on a residential street.
While it helps cyclists feel safer and more welcome, it also helps to slow down traffic speeds as well. Most cyclists feel safer - they don't have to fight for space on the road, and the lines on the road help motorists leave cyclists more room when they pass. More convenient to use when car traffic is clogging the road. Reducing traffic speed in an area - bike lanes take up excess road space or parking space. The result is often a more narrow lane for cars, or fewer cars lanes.