(a) No person shall stop or operate a vehicle at such a low speed as to impede or block the normal and reasonable movement of traffic, except when stopping or reduced speed is necessary for safe operation or to comply with law.
(b) Whenever, in accordance with Ohio R.C. 4511.22(B), the minimum prima-facie speed limit of a controlled-access highway, expressway or freeway has been established and the appropriate signs giving notice have been erected as required, operators of motor vehicles shall be governed by the speed limitations set forth on such signs. It is prima-facie unlawful for any person to operate a motor vehicle below the speed limits posted upon such signs except when necessary for safe operation or in compliance with law. (ORC 4511.22)