2010 Toyota Prius Hatchback

TUCSON, Ariz. -- The traffic-clotted Speedway Boulevard, which cuts a bee-line path across Tucson, received its racy moniker a century ago when the route was a pancake-flat dirt track in the Arizona desert plied by speedy race drivers like the famed Barney Oldfield.

Nowadays, the multiple lanes of Speedway hold a huge volume of traffic each day as Tucson commuters use the east-west thoroughfare to move back and forth across a sprawling city.

So we're driving on Speedway but definitely not at a swift clip -- actually, we're creeping along so slowly in the far right lane that the traffic stacks up behind us.

Our snail's pace is prompted by objectives of a driving contest to determine precisely how high we can push the fuel consumption numbers along a measured route while steering a new third-generation version of Prius, Toyota's best-selling hybrid electric vehicle.

The all-new 2010 Toyota Prius looks like a sharper, crisper, smoother version of the second-generation Prius, which conforms as a mid-size four-door sedan, although the new issue measures lighter in weight, stronger in structure, more powerful in the engine compartment but also more frugal in the consumption of petroleum-based fuel.

Federal EPA fuel consumption scores for the Prius Hybrid Synergy Drive (HSD) system reach 51 mpg for running on city streets in the class of a Super Ultra Low Emission Vehicle (SULEV).

But we're working to earn even higher numbers for our slow-go run along Speedway through Tucson by using a light touch on the accelerator, coasting down the rolling hills and riding the brakes for more battery recharging, even cutting the air conditioner and switching to EV mode for stop-light startups so Prius is propelled solely by the on-board electric motor.

After completing a 12-mile route winding around Tucson, our Prius fuel economy run produced a stunningly high number -- 76 mpg.

Park a 2010 Prius next to a 2009 edition and you can detect subtle differences in the structure and styling, as the new issue runs about half an inch longer and 3/4-inch wider with front roof pillars pushed forward to rake the windshield glass keenly to slipstream-smooth nirvana.

All modifications to the body -- a smaller front grille and smoother prow with crisper corners, the whittled wedge profile, sheer-sliced fender bulges and a lip on the tail deck -- point to aerodynamic improvements so the vehicle moves through air with less resistance, thus conserving energy and fuel.

This new design earns an aerodynamic rating of merely 0.25 cD (coefficient of Drag), which makes the 2010 Prius one of the slickest set of wheels in the world.

The passenger compartment -- long and broad and tall, thanks to the mid-size front-wheel-drive platform with a wheelbase stretched to 106.3 inches -- provides ample room for five passengers on comfortable seats with a pair of buckets in front of a bench for three.

Backseat riders gain almost an inch more legroom (for a total of 36 inches), due in part to the design of thinner seatbacks for front buckets. Rear seats have a folding armrest rigged with dual cupholders and the seatback splits 60/40 to fold down flat and expand the rear cargo compartment.

With rear seatbacks down, the cargo bay contains more than 39 cubic feet of stow space, with access provided through a large rear liftgate. In the cockpit the Prius driver faces a sporty four-spoke steering wheel with a console on the right housing a shifter stick for the transmission. A digital instrument panel streaks across the top center of the dash with cool blue-on-black graphics.

In addition to a digital speedometer and various gauges the display illustrates operation of the HSD energy system with icons providing feedback so a driver can learn how to consume less fuel through efficient driving techniques.

Consider the 2010 Prius as one of the most complex and sophisticated automotive machine ever devised since Karl Benz mounted an internal-combustion engine on a three-wheeled buggy in 1885 and drove into history. First, there's the complexity of the powertrain.

The HSD system developed by Toyota controls all energy produced by on-board gas/electric engines and applies it directly to the front wheels in infinitely variable measures through the electronically controlled continuously variable transmission (ECVT).

It teams a thrifty but conventional 1.8-liter four-cylinder Atkinson-cycle engine that sips gasoline with a pair of high-voltage and high-torque electric motors -- one to turn the front wheels and the other to work so many power accessories as well as crank up the four-pack engine and recharge a load of on-board batteries.

Prius in this new version can run on the gasoline engine or on the electric motor, or in a mode with both plants contributing power simultaneously.

Toyota adds three selectable driving modes:

* EV -- Prius moves solely on battery power at low speed for about a mile.

* POWER -- the throttle increases sensitivity for quicker accelerations and sporty moves.

* ECO -- the economy mode to trim fuel consumption.

The four-cylinder gasoline-fired plant, with dual overhead cams and Toyota's smart variable valve-timing (VVT-i) system, musters 98 hp plus torque of 105 lb-ft.

The permanent-magnet synchronous motor by itself can produce 80 hp and 153 lb-ft of torque. Combined output for the HSD tallies to 134 hp with 153 lb-ft of torque. Supplying electrical juice to the HSD is a direct-current nickel metal hydride (Ni-MH) battery tucked beneath the cabin's back seat.

The acronyms in car safety for Prius include variable gear ratio steering (VGRS) and electric power steering (EPS), electronically controlled brakes (ECB), anti-lock brake system (ABS), vehicle stability control (VSC) and electronic traction control (ETC).

Toyota offers the 2010 Prius in five trim tiers labeled I through V with standard equipment increasing through the tiers and a number of options available like a power moonroof and solar-powered ventilation system plus a technology package with navigation gear, a pre-collision system and Dynamic Radar Cruise Control (DRCC).

Still, Toyota holds the line on prices, as MSRP figures range from $21,000 to $27,270.