Data that exists from before? I suppose you could look at fire issues or structural collapses from before there were strong building codes, but these codes were generally developed specifically in response to issues like fires. In the US (colonies, 1600's) building codes emerged for exactly this reason. Later, George Washington & Thomas Jefferson were instrumental in pushing them further. [0]. They continued to evolve in response to things like massive crowding into cities in the early 1900's by new immigrants living in overcrowded and unsafe buildings [1]
They continue to evolve now, with fire deaths dropping significantly over the past 40 years despite population increases as construction methods and building materials get better [2]
I think it's fair to say that there's a legitimate safety concern in allowing structures not built to normal codes for a permanent structure to become permanent without some sort of review. Although I think that simple street dining-- absent these structures that weren't intended to be permanent-- should be much less of an issue. If a restaurant just has tables & chairs out there then I don't see much of an issue as long as they don't obstruct normal pedestrian traffic.
