N.H. Rev. Stat. Ann. § 248:3

In establishing such through route, the department of transportation shall not require any railroad without its consent to embrace in such route substantially less than the entire length of its railroad and of any intermediate railroad operated in conjunction, and under a common management or control, therewith which lies between the termini of such proposed through route, unless to do so would make such through route unreasonably long as compared with another practicable through route which could otherwise be established.