A published study uses empirical evidence to show that the “Bicycles May Use Full Lane” sign works better than the “share the road” sign for raising the perception that bicyclists are an expected presence on the American road.  While “share the road” was a well intentioned campaign, the ambiguity of the message decreased effectiveness.  Clearer is safer.   Here’s the study:  http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0136973

The Bicycles May Use Full Lane sign is a standard sign in the Manual of Uniform Traffic Control Devices.  It may be used on any road regardless of speed limit.  It explicitly states a principle that is essential for the safe operation of a bicycle, and improves relations between bicycle and motorized traffic by educating the public that the road is designed to serve bicycle as well as motorized traffic.  For guidance on deciding when you should use the full lane, see this piece, “Where to Ride on the Road“.  It is from the excellent resource at azbikelaw.org/  and collates the best advice on choosing positioning from leading bicycling authorities.

The key is a person bicycling has a right and responsibility to decide for themselves where to safely position on the roadway.  Fundamentals of bicycle driving include being predictable, visible, following the rules for drivers, anticipating and avoiding hazards.  It is common for operating conditions to necessitate that people bicycling use the general travel lane.   This sign affirms that right.  The study says that “The Bicycles May Use Full Lane signage showed notable increases in comprehension among novice bicyclists and private motor vehicle commuters, critical target audiences for efforts to promote bicycling in the USA”.   It also draws attention to the web of benefits that a growing understanding and a healthier practice of bicycling allows us to connect to, including realizing greater transportation efficiency and cost savings, increased health, reduced stress on the road, greater mobility freedom, the satisfaction of using our bodies, the independence of self reliance, and a higher quality, more attuned life.

References:

Once again, here’s the study:
“Bicycles May Use Full Lane” Signage Communicates U.S. Roadway Rules and Increases Perception of Safety
More from azbikelaw.org on sharing the road.  This is where I first saw the study (Thanks Ed!):
http://azbikelaw.org/whats-wrong-with-sharing/
The study was done by researchers as NC State University.  They are conservation biologists & “work to unravel the drivers of environmental behavior on which global sustainability depends.”  Bicycling is the most integrative, multidisciplinary, holistically beneficial activity on the planet.
http://www4.ncsu.edu/~mnpeters/
A related post on the “Sharrow” lane marking:
http://azbikelaw.org/bicycles-may-use-full-lane-slm-mutcd-updates/
A related misperception is that bicycles may not delay traffic.  In fact New Mexico is one of 42 States that make it explicit impeding laws only apply to motor vehicles.  This means that people bicycling are permitted to move at speeds that are fitting and natural for their bicycle travel.
http://www.cazbike.org/bicycles-are-not-motor-vehicles-and-why-it-matters/