State law prohibits candidate signs on highway rights of way and on overpasses according to the state code, 69 O.S. 1208 (b). Even within city limits, it is still unlawful to post signs on state-maintained highways, overpasses, and bridges.
More than $4 million dollars and many volunteer hours are spent cleaning up trash, signs, and other debris from the road ways in addition to municipal government expenses. Following the state law reduces these costs.
In addition to reducing costs to the government, the state has instituted these requirements to reduce distracted driving along the state right of way and reduce the risk to the candidate, staff, volunteers, and supporters who might stop along the state road ways to post a sign, which is dangerous.