Europe has some serious success in this. UK is also not that bad, London has "Cycle Superhighways"[0], which are essentially 2 way designated lines with 1 bike

Europe has some serious success in this. UK is also not that bad, London has "Cycle Superhighways"[0], which are essentially 2 way designated lines with 1 bike per line capacity. The problem comes down to coverage patchiness. In some places these lines are simply a marking on the road that will not always be respected by the cars and there are places where you need to cycle among large buses and other vehicles which can get scary if there are many of those. But other than that, even in relatively large cities like London, bike only transportation is very feasible. Even better, if you are not feeling like break sweat, there are hybrid electric bikes where the electric motor will propel you down the road and you can push the pedals only when you want to do it. Bike lines are also good for other personal transportation solutions that are getting popular. Carless transportation in the cities is mostly solved problem actually. [0] https://tfl.gov.uk/modes/cycling/routes-and-maps/cycleways https://tfl.gov.uk/modes/cycling/routes-and-maps/cycleways