We have a bit of a discussion with the administration of our university about putting up posters on the glass doors in our campus buildings.

The hallways have a lot of doors made of glass which would make a great place for people to see information while they walk through. There is a rule here that forbids bill-sticking on these doors with the single reason that if the glass door is not 100% transparent anymore, people will hurt themselves on a regular basis because they cannot see if other people are on the opposite side of it.

For some reason this does not seems to happen though **with every other type of door that is not transparent**.

Is this just bureaucratic nonsense or are there any studies/experiments that actually proof that more accidents occur with glass doors that have an obscured view?