I work in transportation safety, primarily aviation but we also support WMATA. We usually define barriers which prevent, control, or mitigate an accident or und

I work in transportation safety, primarily aviation but we also support WMATA. We usually define barriers which prevent, control, or mitigate an accident or undesired state [0]. Safety systems often require warning signage. Anecdotally, I find that regulators, companies, etc. use signage or safety bulletins than active barriers [0] because they are cheaper and quicker to implement. Even when they implement something like, say, abrasive floor treatments [1], that is only one barrier and likely imperceptible to the public. Warning signage may be helpful, but I am skeptical of its effectiveness (especially as implemented). For example, "ice-warning signs do not have a statistically significant impact on the frequency or severity of vehicular accidents that involve ice." [2] (Disclaimer: Opinions are my own.) [0] https://www.wolterskluwer.com/en/solutions/enablon/bowtie/expert-insights/barrier-based-risk-management-knowledge-base/barrier-types https://www.wolterskluwer.com/en/solutions/enablon/bowtie/ex... [1] https://www.nata.aero/data/files/webinar_documents/preventing%20slips%20and%20falls;%20.pdf https://www.nata.aero/data/files/webinar_documents/preventin... [2] https://doi.org/10.1016/S0001-4575(00)00020-8 https://doi.org/10.1016/S0001-4575(00)00020-8