Mich. Comp. Laws § 247.443

Sec. 43. At such hearing the board of review shall have the right, and it shall be their duty to review and equalize all assessments of per cent of benefits made by the county road commissioners, or the state highway commissioner, for such improvement upon the county at large, or upon any city, and the total assessment made upon the several townships, including the total per cent assessed upon lands benefited therein. Such board shall not review or equalize the assessment for benefits upon particular lands. The persons so appointed as such board of review shall be sworn to faithfully discharge the duties of such board of review.