In todays context we face two major challenges both of which stem largely from the abundance of gasoline driven cars on American roads. On one hand the U.S. and the world is facing high oil prices a looming shortage of oil as oil fields around the world go into depletion. On another hand the whole world is facing a global environmental catastrophe that's destabilizing environmental conditions world-wide. On yet another hand (we must be from Mars) the U.S. style of building cities is wasteful of land and ties our hands to possible solutions because of the highway infrastructure. There is a huge need for change in the transportation technologies common in the U.S.
Why specifically the U.S.? It's that factoid, that we have 6% of the worlds population, have 3% of the worlds oil, yet use 25% of the worlds resources, and consequently do a huge portion of the worlds environmental damage.
Wasteful of land? The highway system, as a way to transport people from place to place, is very flexible but at the same time has a very low density of people per square mile of road surface. By contrast any mass transit system has a much higher density of people per square mile. The issue is the need for cars to maintain a safe following distance. Cars on a highway must be far enough apart so they can stop if the car ahead of them needs to stop.
Looming oil shortage? I'll just say 'peak oil'... It's a scientific model that describes the depletion of oil fields and the inability, as a field ages, for oil companies to extract more oil from the field. This model shows that despite there being lots of oil left in reserves, it is increasingly harder to extract that oil, and in the future the amount of oil available will be less than it is today. That last is because it's expected there are no large oil fields left to discover, and that no large oil fields have been discovered for over 40 years.
Now that I've gone over the incentive to moving to radically different transportation technologies, let's discuss some of them.
Gasoholic Hybrid Todays hybrid cars could be best called "gasoholic" as they do nothing to reduce our dependency on fossil oil. They run on gasoline, and the driver of todays hybrids are still 100% addicted to it. They are in my mind a bunch of hype especially when you consider there are modern cars with higher gas miles per gallon efficiency than the hybrid vehicles.
However the presence of gasoholic hybrids is what enabled ...
Plug-in Hybrid By being able to plug-in the user is enabled to begin to be weaned off gasoline. They are a step forward in reducing dependence on fossil oil, because recall that there is looming peak oil situation which will make it hard to find gasoline. There are several plug-in hybrid vehicles due to come on the market "soon" and lets pray that this does happen. The plug-in hybrid vehicles would not have occurred if it were not for dedicated individuals who developed plug-in hybrid conversions of the gasoholic hybrids, got lots of attention with their plug-in conversions, and caused enough ruckus and interest that the car companies decided to make their own.
The difference between gasoholic and plug-in hybrids is the plug-in variety allows the user to plug the car in to a wall socket to charge the battery pack. The pack is also large enough to drive the car for a significant distance. Since most people drive less than 40 miles per day it's very possible that by plugging in they could drive soley on electric power and not touch the gasoline at all, except on long trips.
There are two variations of hybrid vehicle technology. In the parallel hybrid the gasoline motor and electric motor are both directly connected to the wheels and directly drive the car. In the series hybrid the gasoline motor is used soley to drive a generator that in turn recharges the battery pack. Some of the car makers have taken to using the term 'extended range EV' when referring to their series plug-in hybrid designs. I think these car makers are thinking to burnish their image after being accused of murdering the electric car, and they have to have some way to be selling something they can call an 'electric vehicle'.
Battery Electric A battery electric vehicle has only a battery pack and is recharged typically by plugging into a wall socket. Electric vehicles offer 100% freedom from oil and there are no emissions, from the vehicle. Of course the emissions are moved over to the power plant which created the electricity, however the thing about electrons is they can come from a wide variety of sources. Even though the majority of electricity in the U.S. is generated from Coal, it's very feasible to generate electrons from other sources, and in any cases studies show that even if the electrons are generated from Coal the resulting emissions are less from an EV than from an equivalent gas car. Why? Electric motors are far more efficient than gas motors, there is little transportation cost to move electrons from place to place, and finally the power plants can burn their fuel more efficiently than a gas car burns gasoline.
Ethanol, Biodiesel, other biofuels Biofuels offer an interesting way to sidestep the looming peak oil issue, because the fuel doesn't come from fossil sources. Biological material grows all over the planet and there are well known methods for making alcohol or extracting oil from biological materials. Diesel engines can burn pretty much any oil, it is trivial to convert a gas car to burn ethanol, and Ethanol can be made from a zillion different plant species. Research is going on to bioengineer crops or algae etc to make biofuel production even more efficient, etc.
There's concern now that biofuel production diverts crops and have caused high food prices and food riots around the world. The truth about this is a bit murky. However there is a concern about the total output of biofuels which can be grown agriculturally especially as most land in the world is desert. In some rain forests they have been chopping down the rain forest to plant palm plantations, so they can harvest palm oil, and make biodiesel. Uh, was this the desired result?
Bioengineered biofuels may offer a different way to skin this cat. For example studies have been made of funneling smokestack output into algae vats, the algae absorbs the carbon emissions sequestering the carbon into its body, and the algae can later be harvested to make biofuel which is in turn burned in the power plant.
Fuel Cell Fuel cells have been 10-15 years away for the last 30 years. Sigh. They offer such great hope, you feed them hydrogen and oxygen and get water vapor and electricity. By the way if you're paying attention you might realize that a fuel cell car is an example of a series hybrid vehicle in that the fuel cell is used to recharge a battery pack, and the battery pack is used to drive the electric motor.
I think fuel cell cars are a bit of a boondoggle in it is a wasteful extra step to generate hydrogen. Hydrogen is in a zillion different chemical compounds around the world and is very abundant, but it is extremely rare as an element. Except in stars and interstellar gas. Maybe when we're living in tin cans in orbit we can have hydrogen collectors to gather interstellar gas to drive a fuel cell. But here on planet earth it takes a lot of power to extract hydrogen from any of the compounds it is in. It takes more power to extract the hydrogen than the power which comes out of the fuel cell, meaning fuel cells are a net loss situation. Because it takes electricity to extract hydrogen, why not just use the electricity to run a battery electric vehicle and dispense with the extra complication of the fuel cell?
I believe the best use for fuel cells is in power storage. There are a many alternative electricity technologies that are intermittent.. such as solar energy or wind energy. The wind doesn't always blow when you most need the electricity. If there were an excess of electricity one day the electricity could be used to extract hydrogen from something like water, the hydrogen stored in a tank, and then later run through a fuel cell to generate electricity.
Liquified Hydrogen Some car makers have build internal combustion engines that run on liquified hydrogen. I guess they listened to that 'hydrogen economy' phrase a little too literally. The phrase was meant to refer to fuel cells but gosh you sure can burn hydrogen in a specially constructed ICE engine. But as I just said, why bother, it's a net loss situation.
Compressed Air A small number of companies are developing vehicles that use engines that run on compressed air. The vehicle has a compressed air tank, and to drive you release the air, it flows through pistons, drives the engine, and the car moves. It's a way of storing energy in compressed air and extracting that energy by decompressing the air. Very ingenious.
Compressed air doesn't require any magical breakthroughs in battery technology, doesn't require extracting hydrogen, etc. It just requires using a well known technology to compress air. One qualm is the danger of highly compressed air tanks especially in an accident. The same concern exists for fuel cell and liquified hydrogen vehicles, as both use tanks with compressed gas. The higher the compression the more the energy that's stored in the tank, but also the higher the danger in case the tank breaks.
Water Some cockamamie videos have circulated the Internet claiming to show water being used as a fuel. Sigh. Suckers are born every minute I guess.
Fuel efficient motorcycles Why does American imagination for transportation fixate on boxes that ride on four wheels? There are a number of technologies outside the box (so to speak) of four-wheeled cars, and motorcycles are one of them. There are many motorcycles which get very high gas mileage. My Honda Rebel gets 75 miles per gallon and the Vespa's often get 100 miles per gallon or more. Vespa is due to begin selling a hybrid electric motorcycle that will get 150 miles per gallon efficiency.
There are a few considerations about motorcycles, and these considerations feed into the normalthink mantra which stops a lot of Americans from adopting motorcycle use. A motorcycle rider is unprotected against accident, true, but then that just behooves the motorcyclist to be extra careful and as the motorcycle safety training classes say, to look ahead, scan the traffic around them, evaluate the potential dangers, and plan ahead. Another issue is weather (rain, snow, etc) and it is both a safety and comfort concern. Perhaps it is best to not ride a motorcycle in the snow, but in general comfort is easily taken care of by wearing the correct motorcycle garb.
In many countries around the world two-wheelers (motorcycles, bicycles, scooters, etc) are in the vast majority of vehicles. Clearly it's possible to do this, to have roads that are full of two wheelers rather than roads clogged with four wheelers.
Two-wheeled vehicles can carry more people per square mile of road.
Small four-wheelers or three-wheelers Europe has the Quadricycle vehicle classification, which are small four wheelers that are highly efficient. There are also a range of three wheeled vehicles coming on the market in the U.S. and generally they are high efficiency and sometimes have a cabin to protect the rider from the elements. The Xebra, Aptera and Triac are all three wheeled electric vehicles which have enclosed cabins.
In the U.S. a three wheeled vehicle is considered a motorcycle and as a motorcycle doesn't go through the rigorous safety inspections that four wheelers undergo. This makes it easier for vehicle companies to get into the market due to not having the onerous crash testing expense. There's a consideration that perhaps the vehicle is less safe as a result of not having had testing.
Neighborhood Electric Vehicles (NEV) are low speed electrically driven four-wheeled vehicles. They often look like regular cars (such as the ZENN) but are limited to low speeds. Like the three wheelers this means less safety testing requirements and it is easier for the vehicle marker to come to market.
Electric Motorcycles or Scooters There's a wide range of electric motorcycles and scooters available. They look like their gas burning cousins but there's no tailpipe, no gasoline, etc, just a battery pack and an electric motor. All the things said about gas motorcycles apply to electric.
Electric Bicycles If you get out of the mindset that bicycles are only for recreation .. and start embracing bicycles as a utilitarian vehicle, that can carry cargo, can be used for commutes, etc, it makes sense to add a motor to a bicycle. This has been done for over a hundred years and a MOPED is literally a motorized bicycle. Electric bicycles abound, you can buy kits to convert a bicycle to electric, or you can buy pre-electrified bicycles. Electrifying a bicycle makes it far more practical to ride one, because it extends the useful range of the bicycle, it helps you arrive less sweaty at your destination, etc. Electric bicycles offer commutes at a fraction of the energy cost of any other type of vehicle.
http://visforvoltage.org - is a very good place to learn about electric motorcycles, scooters and bicycles
Mass Transit Why travel in a personal vehicle at all? Why not take a bus or train? In the U.S. we allowed our cities to be built for the convenience of cars, and this resulted in urban sprawl that makes it hard for mass transit systems to have enough population density to generate enough ridership such that the transit system has enough riders to be worthwhile. But in places where there is enough population density, mass transit systems make a lot of sense and are widely used. Manhattanites for example regularly do not own cars because they can get around using the subway or bus system. The same is true in European cities where the people were enlightened enough to not rip out their mass transit systems in the first place.
Robotized Cars Some have suggested that cars with robotic intelligence could automate driving tasks such that individual people would not be driving the cars, and it would be safe to pack cars at a greater density on the road than if humans were doing the driving. This would resolve the issue of wasteful land use. It's also easy to envision the roboticized cars as a service where people rent cars as needed rather than owning cars. This is because a roboticized car could be dispatched as needed perhaps via a cell phone transaction, the robotocized car could drive itself to wherever it's needed, drive the passenger to their destination, then whiz off to the next passenger. Robotocized cars could be electric and automatically seek out a charging station when they need recharging.
Telecommuting and Telepresence Why drive at all? With improvements in communications technology we can only expect online communication quality to increase as time goes on. If telecommunication improves a few more stages it may be possible to have what is effectively a face-face meeting with a hologrammatic image (a la Star Wars) and not even have to drive to your office. Of course a lot depends on the sort of work you do or whatever reasons you have for traveling.