Section 3B.02 of the Ohio Manual of Uniform Traffic Control Devices (OMUTCD) state in part "On two-way, two or three-lane roadways where center line markings are installed, no-passing zones shall be established at vertical and horizontal curves and other locations where an engineering study indicates that passing must be prohibited because of inadequate site distances or other special conditions." OMUTCD Figure 3B-5 gives the method of locating and determining the limits of no-passing zones at curves.
OMUTCD Section 3B.02 also makes clear that there is no requirement that no-passing zones be marked at intersections. No-passing zones may be marked at rural and urban intersections when engineering judgment so dictates. The decision as to whether or not a no-passing zone should be marked at intersections is a matter of discretionary engineering judgment. It should be noted that whether or not a no-passing zone is marked at an intersection section 4511.30 of the Ohio Revised Code prohibits vehicles driving on the left side of the road "when approaching within one hundred feet of or traversing any intersection or railroad grade crossing."
As noted above, studies are made to establish where no-passing zone markings are installed. The resulting logs are the used to mark the no-passing and passing zones. The logs may be accessed from this page; however, the logs are maintained by each ODOT District and are available by county at left.