The extension was originally planned to continue further north to and replace commuter rail service entirely between Boston and Reading. Under that plan, without commuter tracks between Boston and Reading, all Haverhill trains would have continued to use the Lowell Line and Wildcat Branch. That routing was used for all Haverhill service between 1959 and its termination in 1976. (When Haverhill service returned in 1979, it was routed via Reading; only a handful of rush hour trains, plus Amtrak's "Downeaster" service, still use the Wildcat Branch.)