Here are a few technical details that you don’t need to know about to buy a hybrid car, but that you might still find interesting. These technologies are not exclusive to hybrid cars, though you will rarely find all of them on a non-hybrid. We do wish they were more common, though. For example, if more vehicles had a stop-start system and low-rolling resistance tires, vast quantities of pollution would be avoided.

Continuously Variable Transmission
If you are like most drivers, especially in North-America, there's a good chance you've never driven a car with a Continuously Variable Transmission (CVT). Unlike manual and automatic transmissions, the CVTs used in most hybrid cars (and a growing number of non-hybrids) don't have a set number of gears. Operating a CVT vehicle is a unique experience, and although driving one might seem weird at first, it will soon become second nature. If you give it a chance, you'll find that the CVT is smoother and more efficient. Its design allows for an infinite variability between the high and low gear ratios, so it can keep the engine near the most efficient RPM while smoothly shifting the transmission to accelerate or decelerate.

Regenerative Braking
To power their electric motors, hybrid cars need to keep their batteries charged. They can do this in two ways: by using the gasoline engine as a generator, or by capturing energy that would otherwise be lost as heat when braking. They do the latter by using the electric motor as a generator. During deceleration, instead of using the brake pads, the hybrid car will use the resistance created by that generator to slow down the car, generating electricity that is then stored in the batteries. This is one of the reasons why hybrid cars get better fuel economy in the city than on the highway: All those stop signs and red lights help recharge the battery.

Stop-Start System
When a car is idling at a red light, it is getting zero miles per gallon. Hard to get more wasteful than that! Hybrid cars solve that problem by shutting down the gasoline engine when the car is stopped. That wouldn't be much fun if the restart was as rough as in a regular car, but hybrids have over-sized starter motors that allow them to smoothly and instantly re-start the gasoline engine as soon as the driver takes his or her foot of the brake pedal. This doesn't make much difference on the highway, but it is a big help in city driving, helping increase fuel economy, and also improving air quality.

Low-Rolling Resistance Tires
According to the U.S. Department of Energy, between 5% and 15% of the fuel burned in a typical car is used to overcome rolling resistance. Low-rolling resistance tires are simply tires that are designed to minimize the effort that the vehicle's engine has to deploy to make them roll. This is a bit like the difference between an under-inflated tire and a well-inflated one. Most hybrid cars are equipped with them, and according to the Union of Concerned Scientists, they "meet the same federal standards for treadwear, traction, and temperature resistance as regular tires."

Plug-in Hybrid Cars
The next generation of hybrid cars will be "plug-in" hybrids. Two things separate them from the current type of hybrids that you never have to plug in: a longer all-electric driving range, and the ability to not only recharge the battery both from the gasoline engine and from regenerative braking, but also from plugging the car into an electrical outlet. This might seem like a small difference, but in practice, it can mean huge fuel economy benefits. For example, if you drive a plug-in hybrid with an electric range of 40 miles, and on the average day you drive less than 40 miles, you will not use a drop of gasoline and the car will act just like an electric car. It's only for trips longer than 40 miles that the gasoline engine would turn on.

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