Standing on the accelerator produces a pleasant surprise. The Prius launches without hesitation thanks to the electric motor's 295 pound-feet of torque from almost a dead standstill. Merging and overtaking at freeways speeds are accomplished with little fuss. Those wishing to experience the car's outer limits, however, should expect more leisurely progress to a top speed of around 100 miles per hour. Speeding calls for horsepower, and as the Prius approaches its maximum velocity, it relies increasingly on its small gasoline engine for motivation. Toyota says the Prius can accelerate from 0-60 mph in about 10 seconds, anemic by modern expectations, but then we've come to expect a lot. As recently as the mid-1950s, legends like the Chrysler 300 and Buick Century didn't reach 60 mph much quicker than that.

Prius gets its power from a gasoline engine supplemented by an electric motor. In a bit of hyperbole, Toyota calls the combination the Hybrid Synergy Drive. Hybrid it is, synergistic it isn't, not by the strictest definition of the word, which would mean that the total power output would be more than the sum of the outputs of the gas and electric motors individually. This is not the case. The Hybrid Synergy Drive does, however, rely on the electric motor even more than the system in the first-generation Prius, which is how Toyota was able to make the Prius larger and more practical without compromising its low emissions or fuel economy. The current model is 30 percent cleaner than the squeaky-clean first-generation (2002-03) Prius. Toyota claims the Prius produces about one-tenth as much pollution as the average new car. Some have described Toyota's hybrid system as an electric motor with gasoline engine assist, and Honda's system as a gasoline engine with electric motor assist.

By complementing the gasoline engine's horsepower with the electric motor's torque, the Prius makes better use of the energy stored in each gallon of gasoline, while leaving fewer nasty chemical compounds in its wake. The electric motor, which begins cranking out its maximum torque virtually the moment it starts spinning, gets the car moving and helps it accelerate while it's underway. The gasoline engine steps to the fore at more constant speeds, especially during highway driving, where horsepower is more critical for maintaining a car's momentum.

The hybrid system improves fuel economy further by turning off the gasoline engine when it's not needed, like when you are waiting at a stop light or even when puttering around town at low speeds. Any time the driver's right foot requests more motivation than the electric motor alone can provide, the gasoline engine fires up and joins in.

The transmission is non-traditional, too. Prius uses an electronically controlled, planetary gear transmission that functions much like a continuously variable transmission. This system constantly and automatically selects the most efficient drive ratio to get the car moving and to keep it moving.

The EPA gives the Prius a City/Highway fuel economy rating of 60/51 mpg with a Combined rating of 55 mpg. These numbers have generated controversy, however. Hybrid-powered cars tend to achieve high ratings on EPA tests because the cars run on rollers, face no wind resistance, and run with the air conditioning shut off. The electric motor plays a bigger role in these laboratory conditions than it does in the real world. In one of those strange twists of logic often produced by law, Toyota is legally barred from advertising any mileage numbers other than those released by the federal government. Most Prius owners report much lower fuel economy, while others argue this point. Published reports have pegged actual fuel economy at 44 to 48 mpg, about 20 percent lower than the EPA rating.

Emissions are the lowest of any real car available to U.S. buyers. At first glance, hybrids such as the Prius are bettered by electric cars, but electric cars are impractical and must be recharged using another energy source that, in turn, requires fuel. So in the big picture, the Prius is easier on the environment than electric cars are.

The Prius saves fuel and reduces emissions by scavenging energy that most cars waste. Regenerative braking links the brakes to a generator, helping use the car's kinetic energy to recharge the battery whenever the brakes are applied. Along the same lines, the transmission offers a setting that helps recharge the battery when the driver merely lifts off the accelerator and lets the car coast, most beneficially downhill.

The Prius rides on regular, commonly available tires. They are not sporty treads, so don't look for quick and precise left-right transitions. But they are stickier than expected, and quieter than the previous-generation's tires. Some tire noise is evident, no doubt because Toyota skipped some sound insulation in the interest of saving weight. But wind noise is nicely subdued by the car's impressive aerodynamics.

Braking is linear, thanks to enhanced algorhithms in the computer that manages this system. They have made brake feedback more natural, so the brakes don't feel as obviously assisted and as if they were managed somewhere else. Tapping the dash-mounted shift lever to engage the B function (for engine braking) returns a feel much like engine compression braking, as if the driver had dropped down a gear while slowing.

Four adults seem to be about the limit for the soft rear suspension, compressing it to the point where occupants will feel the bump stops on mildly rough pavement. And this is without any luggage. The Prius is better with two adults and two kids.