In general Southampton has been losing market share to Felixstowe over the last few years so it is possible to over read proportion of road /rail at the moment.Thanks, a most interesting and useful post! On the specific point above, it would be interesting to see Southampton's rail share before and after the recent (2021ish?) upgrades for handling 775m lengths.
Oxford (when is it going to finish???) is really needed to help Southampton with more paths /day.
Class 70s are the only loco that can handle 775m out of Southampton at the moment.