As others have pointed out the candidates for doubling are
Maynooth - Mulingar (was two tracks till 1917)
Portarlington - Athlone (always been single)
There are in fact some plans to do something around Greystones also (was in the DART plan of 1996 but the passing loop and station at Redford was never built)
Kerry doesn't need 2 tracks, only investment should be a second platform at Milstreet as that would ease timetabling difficulties
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