It only takes a second. Someone is going about their business and a quick distraction causes them to trip, maybe fall. On a flat surface, this could mean nothing; but near an unprotected edge, falls can pose serious risks and result in broken materials, injuries, or even fatalities. In 2014, falls accounted for 40% of fatalities in construction.
Some risks can’t always be avoided, but they can be managed by putting preventative measures in place. Trips and stumbles may still happen, but railings will significantly reduce the danger to your workers. OSHA standards require employers to use some combination of guardrail systems, safety nets, or harnesses at their worksites.