For years, safety codes and standards have required vehicle impact bollards to protect propane cylinders located in or near traffic routes. But because they lacked well-defined specifications — and untested performance metrics — for impact protection, the Propane Education & Research Council (PERC) funded a two-year study with the National Propane Gas Association (NPGA) Cylinder Exchange Council to determine how code-complying bollard installations performed and how alternative methods of protection would perform.