 The single-track Trentham-Upper Hutt section is to be double-tracked, and will be equipped for bi-directional signalling so that trains can run on either track in either direction between Upper Hutt and Trentham (and possibly later to Heretaunga).The work is expected to improve the operation of both suburban passenger trains to Upper Hutt and the Wairarapa Connection, with a longer loop at Upper Hutt to hold Wairarapa log trains.Until the acquisition of the WMR in December 1908, all NZR freight out of Wellington was carried on the Wairarapa Line.