Trains to and from Brighton and Hove were delayed after a man in a wheelchair was dragged on to the railway tracks by his dog.
The 40-year-old Littlehampton man was taken to hospital after suffering a heart attack during the ordeal.
He fell on to the line at West Worthing Station shortly before 4pm yesterday afternoon (Thursday 30 July).
The man was resuscitated and then taken to the Royal Sussex County Hospital in Brighton in a serious condition.
Trains were disrupted until about 7.15pm.