Is anyone aware of any studies or reseach into the number and type of injuries casued by trips?

I would also like to know if there's been any work into the type of trip hazard, for example:

Does a raised bar 8" off the ground (e.g. that effectively acts as a trip wire) result in the same type of injuries as bar that would be on the ground (e.g. a stubbed toe and stumble).

To me there is a clear difference between the two but I need some data to back up my assessment.

Regards,

Andy