anchor.diff:  link:../src/main/java/ch/petikoch/examples/rxjava/threading/TwoLaneMcDrive.java[]
   
   Same as OneLaneMcDrive, but now with two lanes. There are still few customers arriving concurrently. Each of the lane
  -is either free or there is maximum one customer in the lane. Some we have at each time between 0 and 2 customers concurrently.
  +is either free or there is maximum one customer in the lane. We have at each time between 0 and 2 customers concurrently.
   
   * Parallelism in a execution sense: We can handle two customers at the same time
  -* Parallelism in a logical sense: Like OneLaneMcDrive
  +* Parallelism in a logical sense: like OneLaneMcDrive
   
   There is also no need for backpressure, since the customers arrive "slow " and the McDrive can handle them in time.
   
  
positive.code: Same as OneLaneMcDrive, but now with more customers arriving. The McDrive can't handle all of them "just in time",
  so a wait line (queue) builds up. The longer the example runs, the longer the wait line becomes.
  
  We need some kind of backpressure. We choose buffering (queueing).
  
  === InfiniteLaneMcDrive
  
  
negative.code: Now, we have an "infinite" number of lanes. The number of lanes grows to the point when we have
  enough lanes to handle all the arriving customers "just in time".
  
  We output the numer of lanes (=number of concurrently handled customers).
  
  
  