This came up in 2015, when I wrote a long blogpost trying to delicately dismantle it that, in the end, I didn’t hit “post” on and which you have, therefore, not read.
Anyway, it has come up again: http://www.bbc.co.uk/news/uk-politics-41028234
Mr Williamson is obviously not a rail-using MP, otherwise while out and about on the trains around his Derby North constituency he would have encountered a certain operational flaw in his idea called the Class 153:
So once this carriage is women-only, where do I sit? On the roof?