UP will be constructing two new interlockings on the UP/W line, one of which is just about done. All four crossovers for the new Lombard plant are in, and they appeared to be from scratch; with the rails, ties, plates, and switch frogs all assembled on-site into a total of eight turnouts. As background info, in Lombard, UP/W is a triple-track ROW, mains 1, 2, and 3 are numbered north to south, with Metra using mains 1 and 3 generally. Until completion, I didn't know the order in which the crossovers were to be built, but in hindsight there seemed to be three distinct phases, to wit:
Phase 1: Installation of two turnouts on track 3, one at each end of the plant.
Phase 2: Installation of two turnouts on track 1, again, one at each end.
Phase 3: Installation of four turnouts on the center track (2), to match up with the two turnouts each on tracks 1 & 3.
At each location of the eight turnouts, the existing track, ties, and ballast were removed to make way for the new switches, then re-ballasted after installation. As far as track outages, there was never any continuous outage for any track; much of the work was done during midday and on weekends, but the window never seemed longer than 8 hours or so, which is part of the reason this project took several months to complete. And any time tracks 1 or 3 were affected, Metra service was shifted to the center track, which caused minor delays since they have to load/unload at the nearest street crossing to the station due to no center track platforms...