By the time the second series (700+) Harris cars were being delivered, the design had been improved somewhat. A second window was fitted at the front of the Motor carriages for the guard and/or instructor driver to view the track, along with a window from the Guard's compartment into the passenger saloon, and walkways were added between all carriages within each Block or Unit. These latter changes were retrofitted to many of the 500-series carriages as well, following concerns about safety. While the 500-series trains had rotary flettner ventilators fitted; these were mounted on the curve of the roof and spun off-centre, causing a grinding noise. This was fixed in the second series with the units fitted level to the carriage floor. These units were also later fitted to the clerestory-roofed Tait stock, with their opening ceiling-windows being sealed to reduce maintenance costs.