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It depends on what you mean by efficient, I guess. I like the graphic on this article, https://www.treehugger.com/urban-design/how-much-space-do-pe... It shows how many more people can efficiently use roads while on bikes than in cars. So, if we define efficiency by that measure (obviously this matters more in cities and congested areas), then yes, it's more efficient.
I see that graphic a lot, but it's not a very useful one, because it ignores residential patterns. Most people can't use a bike. So if you displace one car, you're not going to replace it with one bike, much less than 5 that would otherwise fit in the same space. The efficiency question is: what minimizes the amount of collective time people spend getting where they need to go. Bike infrastructure might actually make…
This is simply false. Most people absolutely can use a bike. Maybe not for every possible trip, but for many of them, yes. Just look at the bike rate in the Netherlands, if you don't believe me.
There are a variety of possible modes available, and they can be mixed and matched as people need and want. Driving to a suburban park and ride transit station, taking the train into the city, and then using bike share to get to your final destination, is a perfectly sensible thing.