Boltar wrote:
Why do the trains on the NLL switch over to 25Kv AC at Hackney Wick
and then switch back to DC at Dalston when the 3rd rail is continuous
along that section anyway? Why not just stay on DC and save the wear
and tear on the pantograph?


Mainly because the Class 313s work better on AC than on DC. They were
originally designed as an AC unit with the DC only for the short
section from Drayton Park - Moorgate and reliability suffered when
they first transferred to the North London Line. Of course, from next
year when the new platforms open at Stratford, they will run on AC all
the way from Stratford to Dalston.