9) A person operating a vehicle on a highway, when entering and passing through a work zone described in section 79d(a) where a normal lane or part of the lane of traffic has been closed due to highway construction, maintenance, or surveying activities, shall not exceed a speed of 45 miles per hour unless a different speed limit is determined for that work zone by the state transportation department, a county road commission, or a local authority, based on accepted engineering practice. The state transportation department, a county road commission, or a local authority shall post speed limit signs in each work zone described in section 79d(a) that indicate the speed limit in that work zone and shall identify that work zone with any other traffic control devices necessary to conform to the Michigan manual of uniform traffic control devices. A person shall not exceed a speed limit established under this section or a speed limit established under section 628 or 629.
(10) Subject to subsections (1) and (2)(c), speed limits established pursuant to this section are not valid unless properly posted. In the absence of a properly posted sign, the speed limit in effect shall be the general speed limit pursuant to section 628(1).