A Transportation Alternatives study shows men bike to work 2.6 times more often than women overall, but this gap shrinks dramatically where protected bike lanes are prevalent. The research is straightforward: women's cycling jumps in areas with protected infrastructure and drops sharply where lanes are missing or fragmented, while men's participation is less sensitive to these conditions. This matters because it shows safety infrastructure—not culture or individual preference—is the primary driver of cycling participation inequality, and expanding protected lanes is an actionable equity lever for cities.