Human-driven vehicles are too light to add stability in wind. A trike will blow over with a nice gust. But the two-wheel balancing ones are least stable. A trike can be outfitted with small motor and low-lying batteries to stabilise it. So can a bike but it's still inherently unstable.

Instability is the major deterrent to scooters and motorcycles. The second is exposure to weather. Cold weather sure deters motorcyclists! But sooner or later gas prices will have to deter driving cars. The scooter could end up being the choice of the working poor who must still commute. And eventually, the bicycle. Public transit in suburbs will remain unviable for some time if not for good. Bike to buses? Possible.

I've covered the issue of escalating gas prices on ordinary commuters in other threads. I used examples with actual cases with coworkers living gallons away. Any step away from the car is easally called a step down in living standards. You either use up more time to commute or expose yourself to danger or both. (car > bus: time, car > motorcycle: danger, car > bicycle: time + danger)

As a single example, about 90% of Miami's (Dade County) population will be within 3 miles (many within a mile or two, and almost none past 4 miles) of a station for their "Subway in the Sky" when their 103 mile system is completed.  Local financing is in place, but about 25 years yet to go since the feds cut matching from 80% to 50%.

If the average Miamian lives 1.8 miles from a station, biking to the station, parking or taking a fold-up bike, seems QUITE viable.

Why won't the Fed provide more money? (I know, it's rhetorical by now) Becuse it might help people who aren't rich! No reason the Miami's proposed L can't be built provided it's not ridiculously high-tech. A normal L, yes, but it's a monorail or other amusement park style thing it's aptly named  as it'll be pie in the sky.

One thing. If a lot of transit capacity is needed cheap, there are the old fashioned yellow school bus! No A/C but windows can be opened! That would be the "Cuban method" of ramping up transit cheap. Use what you already have, since the Fed's priority is the No Billionaire Left Behind tax cuts and gratuitous wars.

I just found out that my bike dealer is getting a few ZEM quadracycles in this month, so maybe I can try one of them:

www.zemusa.com

He doesn't have much use for Rhoades Cars.

Lightfoot claims their semi-upright utility trikes are as stable as any quad:

http://www.lightfootcycles.com/index.htm