ION - Waterloo Region's Light Rail Transit

[tomh009]

So 504 is the final design then? How are they going to handle this with 501/502? I can see them shipping 501 back but 502?

Designs are rarely "final". Tweaks are often made to "final" designs to make manufacturing go smoother, make maintenance easier, make things last longer, etc. Most of the tweaks are things that the average person would never see. The majority of tweaks to the design are usually made within the first 50-100 production models manufactured.

Similarly, the 100th Boeing 787 is a far, far better airplane than the 10th one off the line.  Boeing had to do extra-heavy discounting in order to find buyers for the "terrible teens", before the 20th plane.