I've had the option. And I certainly wouldn't. When we lived in Sweden (DD was 16 to 26 months old in that period), we biked around a lot. I don't drive, and biking is quite common there, with lots of bike lanes, and the area we lived in had not so much traffic, good vision, 30 km/h speed limits and an expectation that kids will be playing in the street. We had a Weeride for her, and we both wore helmets. However, coming home on the bus with DD asleep in the mei tai, I could chose between biking with her still in the mei tai, wake her and put her on bike, or walk 2 km. I usually opted to walk, and would never choose to bike babywearing. we talked about it and read up on the safety before deciding this. I did fall with her on the bike once, on an icy patch, and several times we nearly fell. All you need is something in the road that shouldn't be there (and in the dark or rain this is really difficult to see, despite bike lights), and you go flying.