Several days ago, I wrote about the carriage shortening of 4103F set fo Tokyu 5050-4000 Series. I wrote why 4103F had been shortened was to make up for 8-carriage set damaged in the accident on February. But I found another reason, picking a motored carriage to return a 5000 Series set to Den-en-toshi Line.
Four middle motored carriages of 5050-4000 Series, 4601, 4602, 4603, and 4604, were originally manufactured as the one of 5000 Series on Den-en-toshi Line and their interior colour are different from the other 5050 Series, blue longitudinal seats and purple-blue-coloured protection on the seat end.
Though there is no official plan for introducing newly-made carriages in 2014, if 5050 Series keep being manufactured this year, these sets will seem to replace 5000 Series on Toyoko Line, 5118F, 5119F, 5121F, and 5122F. When 5000 Series rearranging to 10-carriage train to come back, the middle carriages of 5050-4000 Series are needed.
I would like to correct my forecast to that 3 sets of 8-carriage 5050 Series and 4 non-motored middle carriages of 5050 Series (5470, 5570, 5471, and 5571) and 4 motored middle carriages of 5050-4000 Series (4601, 4602, 4603, and 4604) will be manufactured fromthe one before.