Network Rail has completed an £11m two and a half-year project to renew and replace sections of track at 59 sites along the Highlands' Far North Line.
The work included replacing 36 miles (58km) of rail and more than 11,000 sleepers.
Also, fixing 40 track faults between Thurso and Georgemas junction.
Engineers had to contend with bad weather and damage during the "Beast from the East" storm that hit last March.
Network Rail said that in an "innovative first" for Scotland's railway the 1,100 rails used in the work were delivered by sea to Scrabster, near Thurso.
The company said this saved making 110 road freight journeys and reduced carbon emissions by about 200 tonnes.