N.H. Rev. Stat. § 246:2
Upon petition of a railroad, the selectmen of a town, or the mayor and council of a city, the department of transportation, after notice and hearing, may require a railroad (a) to separate the grades where a highway and railroad cross at grade or where a railroad crosses another railroad at grade, (b) to change the location of a highway or a railroad in order to avoid or improve a grade crossing or (c) to reconstruct or otherwise alter or improve any existing bridge or underpass and the approaches thereto in instances where separation of grades has been effected, or (d) to improve the approaches to any grade crossing so as to make them as nearly level as practicable where any such action is found necessary in the interest of safety to the railroad or the public. At any such hearing, the director of the division of motor vehicles shall sit and confer with the department of transportation in an advisory capacity in the determination of the necessity for such reconstruction and the apportionment of the cost of the same.
RSA 246:2
1937, 123:1. RL 299:2, 3. 1951, 203:58 par. 2. RSA 373:2. 1985, 402:6, I(e)(5).