Changing light bulbs on overhead signs
Washington DOT does not have a strict requirement that lanes be closed while changing lights or doing other overhead work that takes place over a live lane, but it is strongly recommended and considered a “best practice” that the lanes be closed. There has been discussion about adding this requirement to their specifications.
The key issue is the vertical clearance for the work crew to the live lane and the visual distraction that occurs due to the work operation. Their signal maintenance crews perform work over live traffic on occasion, but this practice is being looked at more closely as to whether it will be allowed to continue.
Labor & Industries has a requirement for securing tools to ensure they cannot fall when working overhead.