Bike lanes are a great way to promote cycling in cities, they provide a buffer for cyclists and make riding safer. That is, if cars don't park in them, they are clear of debris and they actually lead anywhere. Another problem with bike lanes is that they create vehicular conflict/confusion when it comes to turning; cyclists are stuck in the right hand lane which can be a problem when they want to make a left and can be caught between a right turning vehicle and the curb at intersections. Because of the segregated nature of bicycle lanes, many drivers and cyclists, are left wondering how to negotiate with these issues. This can result in cyclists riding on the pedestrian cross-walk in order to make left turns, or cyclists attempting to pass drivers on the right hand side of a vehicle which is attempting to make a right turn (which can lead to the devastating right-hook). Cyclists such as John Forester suggest that bike lanes should be eliminated and that cyclists should act more like drivers in cars should in order to promote safer cyclist/driver relations on the road. Though this can be possible it's something we are far from accomplishing and something I'll rant on sometime later.
In Toronto, there are a few examples of bike lanes that actually take these conflicts into consideration. Often, you will see bike lanes suddenly disappear at intersections which can create confusion and danger. The photo below was taken at Old Fort York & Bathurst where a bike lane splits into 2 lanes, one for right turning bicycles and another for left turning. Both are well supported with indicator arrows and a buffer on the left turning bike lane also adds to the safety. Of course, this may not necessarily work at every intersection as such a scheme requires a lot of lane-width and must also take into consideration traffic speeds as cyclists must exit the bike lane, merge into traffic and then merge into the left turning lane. Still, this is a nice example of the city trying to look out for cyclists and drivers.