Taken from this months Modern Railways (Jan15) which has an article on SWT and expected growth up to 2043. (Page 10/11).
“There are a few services which can be lengthened to ensure that all operate at there maximum formation, and SWT is looking at resourcing the necessary rolling stock to do this. A further 2tph (trains per hour) could be provided using the existing infrastructure, although the report expresses concern that this could have a negative impact on performance. It also suggests the provision of 3+2 seating on Class 158,159 and 444 Units (which currently have 2+2 seating in standard) as a means of raising capacity, whilst recognizing that the 3+2 seating configuration is unpopular with passengers”
Report is written by Network Rail and South West Trains Wessex Alliance.