Cycle lanes DO cause more congestion if they're badly planned/installed!
One particular busy junction in particular used to be two lanes - one for straight on/turning right, the other for turning left. Never any significant congestion/queueing in either direction. It worked well.
They removed the left lane by hash-marking it and white-lined a cycle lane instead. So now all traffic has to use what was previously the right hand lane, for going straight ahead, turning right or turning left. Of course, now it's backed up constantly as the cars turning left have to wait for cars turning right, which in turn have to wait for cars coming in the other direction to clear, so it basically holds everyone up! I've seen queues as long as a mile back, which in turn cause congestion at other junctions along it!
What's even more stupid is that there is no cycle lane before or after that junction, so bikes are in normal traffic flow, then they have about 50 feet of their own cycle lane which causes the chaos, then after the junction, they're back in normal traffic flow. Surely it's more dangerous for them to have to cycle alongside a long queue of traffic, weaving in and out, having to watch for pedestrians/traffic turning through the queue of traffic in their path, etc?