NASHVILLE, Tenn.—Nissan’s fifth-generation Altima began rolling off the production line at the company’s Smyrna assembly plant on May 15. Now the question is, how fast will the redesigned model roll off dealers’ lots?

It’s a fair question because the important mid-sized auto segment is going to be increasingly competitive in the coming years.

Both the Toyota Camry and the VW Passat are new for 2012. Altima, the Honda Accord, Chevrolet Malibu, and Ford Fusion are in the process of launching 2013 redesigns with a new Mazda6 coming in 2014.

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The outgoing Altima, despite being in its sixth year on the market, not only is Nissan’s top-selling vehicle but also had its all-time best sales year in 2011, when it was the second-best-selling passenger car in the United States, trailing only the Camry.

Altima isn’t likely to pass Camry in the near future, but the new version is a terrific package, upgraded across the board. For Altima fans, the good news is that it’s still their beloved Altima—just noticeably improved.

Nissan’s presence in the Nashville area is unmistakable in both its North American headquarters building and production plants in the suburbs, plus the high-profile downtown sponsorships at the Bridgestone Arena (home of the NHL Predators) and historic Ryman Auditorium.

That’s a reflection of the company’s Americanization and its status as the No. 1 non-domestic manufacturer in North America. Each generation of the Altima has been built in the United States and more than 4.4 million have been sold so far in the car’s 20-year history.

In the short term, because fuel economy is a hot topic, we’ll hear a lot about Altima’s segment-leading 38 miles per gallon highway mileage rating. That’s for the 2.5-liter four-cylinder version, which Nissan anticipates will be 90 percent of sales. The 3.5-liter V-6, meanwhile, has a preliminary 31 mpg highway rating.

On the road, the I-4 proved to be smooth and capable and would be my engine of choice. For the 10 percent who feel the need for more power and refinement-smoothness, the V-6 delivers just that.

Nissan, the industry leader in CVT transmissions, has advanced this component with an expanded gear ratio range (equivalent to an eight-speed automatic) and 40 percent less friction, and did so in a smaller package.

Nissan has eschewed direct injection in favor of other mileage-enhancing tweaks, including a “smart” alternator that only engages (drawing engine power) when the battery needs charging.

In addition to its significant fuel mileage numbers, Altima has evolved on all fronts, which is important to the traditional Altima buyer, who is drawn to the car’s looks, driving dynamics, reliability, and state-of-the-art technology.

Outside, Altima is changing by an inch all around—an inch lower, an inch wider, and an inch longer. Nissan used advanced deepstamping metal fabrication techniques to make more defined accent lines that complement the Altima’s aerodynamic look. It’s done subtly. A casual glance shows so many styling cues have been retained that it looks more of an evolution than redesign, a wise decision because Altima’s distinctive styling has made it stand out in the mid-sized market.

Inside, the look is decidedly more upscale with upgraded materials, better sound absorption, an NASA-inspired comfortable seat design, and a new advanced 4-inch color driver-assist display in the center of the instrument cluster. The display shows navigation, blind spot warning, Pandora radio, and tire pressures at a glance.

Enhancing that tire pressure readout, Altima has an “Easy Fill Tire Alert” system. Start putting air in a tire and the parking lights flash. When the tire reaches the optimum pressure, the horn sounds.

Another enhanced bit of technology is the four-way rear camera. In addition to serving as a visual parking assist, it now is the source of information for the Blind Sport Warning system, lane departure warning, and moving object detection, alerting drivers of cross traffic behind them when backing out of a parking spot.

An “active understeer control” is built into the new Altima. However, the average driver never will know it’s there because it doesn’t advertise itself with a warning light or sound. The system will activate the inside front wheel’s brake proactively to help keep the vehicle on its intended route in a situation such as taking an off ramp too fast.

The Altima is part of Nissan’s planned 5-model rollout over a 15-month period. Coming this fall will be both the new Sentra and a Pathfinder that already is causing a buzz. After that, Nissan is promising a volume hatchback and crossover.

Those five vehicles are projected to represent 70 percent of Nissan sales, a big number for a company that has its sights set on improving its present 8.2 share of the US market (up from 7.8 percent in 2010) to 10 percent in the next few years.