Great information from Greg Ubic of the Cleveland Touring Club, who shared this very helpful analysis of 4511.55 in an e-mail to the club's mailing list:
ß 4511.55. Riding bicycles; motorcycles abreast.
(A) Every person operating a bicycle upon a roadway shall ride as near to the right side of the roadway as practicable obeying all traffic rules applicable to vehicles and exercising due care when passing a standing vehicle or one proceeding in the same direction.
(B) Persons riding bicycles or motorcycles upon a roadway shall ride not more than two abreast in a single lane, except on paths or parts of roadways set aside for the exclusive use of bicycles or motorcycles.
(C) This section does not require a person operating a bicycle to ride at the edge of the roadway when it is unreasonable or unsafe to do so. Conditions that may require riding away from the edge of the roadway include when necessary to avoid fixed or moving objects, parked or moving vehicles, surface hazards, or if it otherwise is unsafe or impracticable to do so, including if the lane is too narrow for the bicycle and an overtaking vehicle to travel safely side by side within the lane.
Section 4511.55(A) is very often misquoted to say that cyclists are required to ride as near as possible to the curb. The new paragraph (C) should help reduce this confusion. There are many conditions where it is much safer to ride near the middle of the lane.
It is not practicable (practice-able) to ride on the far right when passing or turning left; or when avoiding objects, parked cars, moving vehicles, pedestrians, animals, surface or other hazards; or when the travel lane is too narrow for a bicycle and another vehicle to pass safely side by side within the lane. Many motorists are reluctant to cross a lane line when passing a bicycle. A cyclist who "hugs the curb" unintentionally invites motorists to pass with unsafe clearance. Riding near the middle of a narrow lane sends the message that passing traffic must use the next lane.
The real purpose of this law is to prevent unnecessary delay to faster traffic. Since the law cannot require unsafe operation, the phrase as close as practicable is highly flexible, varying widely according to conditions. Positions well away from the edge of the road can be in compliance.
Section 4511.55(B) allows riding two abreast. However, cyclists should avoid unnecessary delay to other traffic. Please be courteous and "single up" when other drivers wish to pass if such passing is safe and reasonable. There is no violation if any of the following apply: (1) If there is no traffic being delayed; (2) If the cyclists are traveling as fast as other traffic; (3) If traffic can reasonably pass by using another lane; (4) If the lane is too narrow or it is otherwise unsafe for passing.