N.H. Rev. Stat. Ann. § 230-A:11

All property interests taken under this chapter shall be in the form of a corridor protection restriction, unless the layout authority or its designated agent makes a written finding that the public interest requires taking a greater property interest in the property. Reasons for such a finding may include, but are not limited to, a probable likelihood that the layout will eventually require a taking of greater property interest, or a substantial similarity between the appraised value of the greater property interest and the corridor protection restriction. The layout authority may amend the terms and duration of any corridor protection restriction to meet the needs of its planning process, but the duration of any term thereof shall not exceed 10 years, unless renewed.