In last week's program there was a derailment of the last motor car of a train and considerable delay occurred as on a Sunday they waited for a cleanup crew to deal with human waste on the track before the technicians, understandably, could get to work. Then this week they showed regular maintenance of the tracks between the platforms which included cleaning the human waste away. Actually a scene I could have done without viewing.
It surprises me, as all the trains shown are fairly modern and I would have thought they would all have retention tanks. Even our heritage trains here in Dunedin have tanks and we have to assure passengers they can use the toilets at any time. Some become concerned when they see the water from the washbasins going on the line. I would have thought all trains in regular modern service today in the UK would have holding tanks.