Few know what "hybrid" means, much less the benefits and drawbacks of hybrid vehicles. Fortunately, all the average motorist needs to know is that the hybrids of 2020 will get a lot better fuel mileage with only a moderate loss in acceleration and load-carrying capacity.

A hybrid is a combination that produces something that's better than the originals by themselves. Examples include Big Boy tomatoes, which are easy to grow, bountifully productive, long lasting and disease resistant. Non-hybrid "heirloom" tomatoes, such as Brandywine and Cherokee Purple, are more flavorful but are harder to grow, produce few fruits and spoil quickly. Another example: A mule, which is a cross between a female horse and a male donkey, is stronger than a horse, has more endurance than a donkey and is more resistance to disease than either.

Current hybrid vehicles combine conventional gasoline-powered piston engines with electric motors and batteries. Most automakers now choose to use this combination to give the vehicle the power needed to merge into fast-moving interstates while offering better fuel mileage than a gasoline engine large enough to produce the same acceleration. Only a few hybrids focus more on producing better fuel mileage in exchange for less potent performance.

The batteries in current hybrids are charged both by the gasoline engine and, to a far lesser degree, energy captured when the vehicle slows down. When you coast or touch the brakes, the electric motor turns into a generator to recapture energy that would be otherwise wasted. Hybrids also save fuel by turning off the gasoline engine when the vehicle is sitting in traffic.

Current hybrids cannot run any useful distance on battery power alone: We've yet to find one that'll go 100 yards without the gas engine starting. This is because battery life is severely reduced if its energy is fully drained or charged. This means most hybrids don't allow their batteries to drop much below a 50 percent charge nor exceed an 80 percent. This must be done to assure the batteries will last the eight to 10 years required by many state governments. If the battery charge were allowed to drop further or climb higher, hybrids would require a new $5,000 battery pack well before the warranty expired. Automakers say their batteries are "designed to last the life of the vehicle" and initial reports indicate they're succeeding: Toyota Prius' employed as taxis in Canada have racked up more than 200,000 miles.

The next major step in hybrids will be "plug-ins". These allow the batteries to be recharged with cheap household electricity. Drawbacks include lack of easily accessible electrical outlets near parking places, the requirement to carry more batteries and the need to build new coal-fired or nuclear power plants to meet increased electrical demand.

Further away are hybrid vehicles that are mainly electric vehicles. They will have a small engine (perhaps a diesel) but it will only be used to charge the batteries. The plug-in feature will also be available to charge the batteries. However, this technology depends significantly on adapting lithium-ion (Li-ion) batteries for automotive use and mass-production. Li-ion batteries are lighter than the currently employed nickel-metal hydride (NiMH) batteries. That means the vehicle can be equipped with more Li-ion batteries and, thus, store more electricity. However, Li-ion batteries do not tolerate deep discharging much-if any-better than NiMH. Automotive Li-ion storage cells will be significantly different than those in your laptop: They won't employ the flammable liquid solvent used in laptop batteries. Current thinking says an inert polymer will be employed instead.

Hybrids are not as environmentally friendly as some imagine. NiMH batteries cannot currently be profitably recycled. Without subsidizes collected from hybrid buyers and given to recycling centers by auto manufacturers, the batteries would sit in landfills waiting for the price of nickel to rise. Right now, it's cheaper to mine more nickel, with the associated environmental destruction. Also, some say Li-ion batteries are even less able to be recycled and NiMH.

Further over the horizon are electric/fuel cell hybrids. These will use an electric motor to power the car and a fuel cell to charge the batteries. Fuel cells are currently in use in spacecraft among other places. Some automakers have a few early prototypes running on the road. The fuel cell converts hydrogen, methanol and other fuels into electricity through a catalytic process that requires a Master's degree in chemistry to understand. The output of a fuel cell is water and carbon dioxide. However, making hydrogen and methanol are energy intensive operations.

Some inappropriately question the crashworthiness of hybrid cars. Rest assured, hybrids are at least as safe as a car with 20 gallons of gasoline behind the rear bumper. Metal cases that surround batteries in hybrids are designed to withstand virtually all survivable impacts. If a collision is severe enough to set off the airbags, the hybrid's high-voltage system is instantly switched off and the electricity is contained inside the metal battery case. And there's a deceleration sensor as a backup. In less serious situations, rescuers can disable the high-voltage system by turning off the ignition, removing the ignition key or moving the keyless electronic fob at least 16 feet away from the vehicle, all of which are standard procedures for conventional cars. Also, for all vehicles, first-responders are trained to disconnect negative terminal of the 12-volt battery or cut the negative cable if they're unable to switch off the ignition. These actions kill the engine and disable airbags and seatbelt pretensioners. With hybrids it also prevents current from flowing from the high-voltage battery.

Hybrids are not the only way to reduce our use of petroleum, but count on them to lead the way.