“The West of England line is built predominantly on clay - a particular type of clay with high plasticity. When there is a soil moisture deficit (an absence of moisture), the structure starts to collapse. “But as we hit April, and the start of soil moisture deficit, that quickly deteriorates. He told the rail users that the soil moisture deficit was worse than experienced in 2022, when similar timetable-cutting was required. The West of England line issue“There are long sections of single track which constrain timetabling,” Prof Powrie points out.