I'm about to get a motorbike and, while this is in no ways reasoning for getting the bike (it's pretty much entirely for fun), it's had me thinking a bit about the social impact of motorbikes/scooters, especially if they were widely used (like they are in India, South-East Asia, and a couple other places) for commuting.
They're obviously more efficient in many ways. Less fuel usage, less material required to manufacture and transport, less space required both when driving and for parking, less infrastructure maintenance cost, etc. However, they're less efficient for all these things than the solutions mostly advocated by this and similar communities - namely public transport, cycling and walking. All of which are significantly better.
In contrast to those alternatives, though, motorbikes need basically no infrastructure development to be used, so it would be far easier to make incremental progress with individuals riding a bike instead of taking the car, rather than requiring organised political action.
Specifically for the USA and, to a lesser extent, the more similar countries like Canada and Australia, it's probably also more socially acceptable to not be riding public transport with the plebeians, or having to do physical exercise. And you can easily overcompensate with a massive bike, while still being far better than the massive cars coming out of the US - a litre bike is big, while a litre car is tiny. Obviously this isn't a 'good' reason, but it does seem to be a real consideration.
The main counter-argument I can think of is safety. But if you look at the countries where motorbikes and scooters are common, they seem safer than riding a motorbike in Western countries (anecdotally, from people who have ridden there on trips but wouldn't think of it at home; if anyone can find statistics for it, I'd love to see them). I'd say this is because of their prevalence. You'd get rid of the selection bias for risk-takers, and for high-power bikes. You'd also reduce the issue that car drivers aren't aware of motorcyclists, and often don't notice them. Any collision that does happen would also be more likely between two motorbikes, which would be less deadly than a motorbike and a car. And if we transpose this prevalence of motorbikes to a western country with stricter regulations around licensing, required safety gear, road rules, etc., surely this would be even less dangerous than it is in those countries.
Also, the safety argument seems quite similar to the safety argument for large SUVs for ferrying kids to school. Inside the car, you're safer, but that's at the cost of safety and health of those outside the car, as well as all the other negative effects we're all aware of. Obviously it's not quite to the same extent, but it just strikes me as similar.
So, those are my opinions, which ended up a bit longer than I was expecting... But the reason for posting is that I'd love to hear yours. Do you think largely replacing cars with motorbikes would be beneficial but insufficient, infeasible, or do you think it would actually be worse?