You're comparing a situation that happens all the time (opposing traffic) with one that happens extremely rarely (blocked stairwell in a fire). If anything, you

You're comparing a situation that happens all the time (opposing traffic) with one that happens extremely rarely (blocked stairwell in a fire). If anything, you're strengthening my point. We should design for situations to a level that is appopriate given their frequency and severity. Show me evidence that MANDATING the extra stairwell justifies the huge increase in national housing cost, and I'll concede.