What if you could decrease the US's oil consumption (and the foreign dependence requisite therein), cut greenhouse gas emissions, increase general public health, reduce obesity substantially, and preempt cardiovascular deterioration in one stone's throw? It isn't difficult to imagine how it could be done, they're all related problems.
In the USA:
Percent of all energy consumption that is used for transportation: 29
Percentage of that energy used that comes from oil: 95
Percent of all trips that are 3 miles or fewer: 50
Percent of those that are driven: 72
Percent that are by bicycle: less than 2
Percent of all trips that consist of driving 3 miles or fewer: 36
Percent of bicycle trips that are 3 miles or fewer: 85
Estimated average speed of a moderately fit cyclist: 12 mph
Time for this cyclist to cover 3 miles: 15 minutes
Estimated time for a lawful driver (regardless of physical fitness): 15 minutes
Estimated gasoline used by the car to cover 3 miles: 0.1215 gallons
Amount of energy this represents: 15,800,000 joules
Estimated energy expended by the cyclist: 135,000 joules
Estimated additional food calories the cyclist burned: 32
Estimated total food calories the driver burned: 29
Amount of food calories the car burned: 3,775
Food calories in a gallon of gasoline: 31,070
Example daily Caloric intake of an ultra-endurance athlete: 6,000
sustained horsepower of Lance Armstrong: 0.67
sustained horsepower of an average male: 0.20
In Amory's video below, it is mentioned that less than 1% of the energy consumed in moving a vehicle is moving the driver - obviously, too, the car weighs an awful lot more than you do and weight costs energy to move. So we are wasting 99% of our highly condensed energy to move a hulking steel shell a couple of miles. Cars are great vehicles for moderate distances, 30 miles and up at least, but they're too wasteful for anything less--just the same as how you wouldn't taxi an airplane to travel a few miles.
But wait, weren't we supposed to be talking about health? Where does health fit in? Right here.
Bicycles. Yes, they've been around for ages, all the laws regarding their use are (internationally) in place, they're cheap, familiar enough in culture to not be mocked (ahem, Segway), and just about every business has some kind of object a bicycle can be locked to, usually closer than the handicapped parking space. The bicycle is a legitimate form of transportation; having ridden a bicycle the ~3,600 miles that span the US this is a statement in which I have authority to represent. A healthy human being can sustain an average of 15 miles per hour for one hour without much problem. The result is that anything within a few miles of where you are is a short bike ride away. For me, and I'm nowhere near as in shape as I was, riding my bike 3 miles takes about the same time as in a car. When closer, the bike is definitely faster in most cases, and a whole lot more pleasant. Of course, the more you ride a bike the more fit you become, and so forth. If everyone were to abandon their cars for short distances, the streets would be flooded with cyclists. You wouldn't need to worry as much about being hit by a car because there wouldn't be near as many cars, and many of the people who were driving would realize what it would be like to be a cyclist and would drive more defensively. Bicycle collisions aren't much of a worry, nothing like auto collisions which are the 4th greatest cause of death in the US--cars are, to people, a disaster; the human brain is not built to process the number of things at the speed required for driving, as much is clear in the amount of accidents that happen every day. Add on top of this our increasing distraction by the fast pace of modern life (drivers on cell phones, grrr) and that a four thousand pound vehicle (such as an average SUV) moving at 35 mph has tremendous kinetic energy, about 11% of a stick of dynamite: kinetic energy is 1/2 * mass * velocity squared, which ends up as 222,088 Joules. A stick of dynamite has around 2.1 million Joules of energy, so the percent of dynamite's energy the vehicle has is 10.6%. The result is clear: people just shouldn't be allowed to drive, we aren't capable of doing so safely. I love driving a lot, but there is no question here, no way to justify allowing people to drive. The way to make a vehicle inherently safer is to reduce its energy, which means lighter and slower; bicycles are singularly wonderful in that they represent one of the lightest forms of transportation conceivable, however even they are not perfect, as in the wrong hands they can be tricked into traveling at dangerous speeds ;)
Pushing cars off the road and people into the streets with motivation/education for physical fitness is, very unfortunately, not enough. We need to truly revolutionize our understanding of existence--not a new same-as-usual car with an astonishingly expensive marketing campaign that uses the word "green" a lot. In this small domain of personal, local transportation we already have the technology, we just need to use it!
The craziest thing about the low utilization of bicycles is that self-powered transportation would be an overwhelmingly positive thing for the majority of people. It comes down to health, wealth, and happiness.
Wealth is obvious, bicycles are a lot cheaper than cars, even absurdly expensive bicycles. 17% of the average USAmerican yearly income goes to transportation, which is the second largest spending category after housing. Furthermore cycling naturally supports the very local economy, which the cyclist necessarily participates in and at least indirectly benefits from. The savings can even be realized directly with participation in the Bicycle Benefits program, with presently almost a hundred local, conscientious businesses (some of my favorite) offering incentives such as 10% off purchases.
A widely accepted goal for life is to live a long and healthy life. Healthier lifestyles would substantially reduce the majority of deaths, including their often extensive associated medical care/cost, by the biggest killers (followed by the chance any person will die from it):
1. Heart disease, 1 in 5
2. Cancer, 1 in 7
3. Stroke, 1 in 24
4. Motor vehicle accident, 1 in 84
5. Suicide, 1 in 119
I included suicide because there is evidence that shows exercise effective in mediating the symptoms of depression. There is no reason I know of to imagine that an active society will have significantly reduced cancer rates (except for the decrease in environmental pollutants), as the many causes of cancer aren't so well understood. For the next greatest causes of death some arguments could be made for the effectiveness of cycling in prevention, though they get weaker: number 6, falling, could be diminished by increased muscular fitness of elderly folks and increased spatial coordination for (tragically) clumsy people; number 7, firearm assault, could be decreased by the increase in social interaction that is inevitable when you aren't enclosed in a glass and metal box and by increasing the wealth of immediate neighbors through the support of local economy. Number 8, pedestrian accidents, would clearly decrease with the amount of cars on the road and number 9, drowning, could also decrease with increased general fitness. Of course each of these causes have instances in which the fantasized bicycle culture won't help, but there is little question that increased mean health of the population ultralight human powered vehicles would have an incredible impact on healthcare expenses. There is no other way to say it but that bicycling is a miraculous thing that a (growing) few take advantage of. Riding a bike leaves the air cleaner, your self happier and your body healthier, where's the downside? You can't say safety because cars aren't safer, car accidents kill way more people than bicycle accidents. There is no downside, ride your bike.