In an Instructor seminar last Spring - I saw a brief presentation about running helmets with visors in cars with airbags. The concern was in an impact - the airbag catching the edge of an open visor and violently rotating the helmet backward (rotating bottom-to-top) as the airbag inflates. This was apparently driven by real-world incidents.
The guidance/recommendation was to have the visor open no more than two fingers (index and middle) wide.
Just thought I mention it because it had never occurred to me.