Platforms 3 and 4 at Commercial - Broadway are strangely numbered as they are the original station platform for the Expo Line. Millennium Line trains stop their as well with the optional transfer provided to those same trains since they form a giant loop. The stop has a single island platform with an up escalator/staircase, elevator, staircase, and two escalators leading down to a street level station lobby at the SE corner of Broadway and Commercial Drive. At the northern end of the platform directly between the two tracks (that stay apart) a bridge crosses over Broadway and leads to the upper level of the Millennium Line station entrance where a set of escalators, a staircase lead down to it for transferring passengers.
The station was heavily expanded in 2019 with the opening of a new (Platform 5), this is a side platform for exclusively for the use of Waterfront-bound trains, with these trains now opening their doors on both sides (also to the island platform) of the track (something very easy on an automated train with no onboard staff, fully driven by computers). This side platform contains a modern glass wall, with a lattice structure beyond it, and its own escalators and stairs down to the modern and larger fare control area below. The main reason the new side platform was built was to supplement the current narrow bridge that leads to the end of the island platform that all passengers transferring between Expo and Millennium Line trains must walk over, at the end of the side platform there is now a separate bridge (with the trackway in-between) across Broadway to a separate bank of escalators (and an elevator) down to the Millennium Line platforms (and their own fare control area).
Photos 1-8: 7 October, 2011, 9: 8 October, 2011, 10-14: 16 April, 2014; 15-32: October 13, 2022