TURIN – BMW will signal an all-new model range when it pulls back the covers on the Concept 4-Series Coupe that will bow at the North American International Auto Show in Detroit next month.

Although billed as a concept, the car represents the first look at the upcoming 4-Series line that slots between the 3- and 5-Series and joins BMW’s other even-numbered models, the 6- and 8-Series.

It is the second step in BMW’s quiet revolution after the recent introduction of the front-wheel-drive Concept Active Tourer model at September’s Paris auto show. Both new lines are aimed at expanding the auto maker’s market reach with increasingly diversified products.

The 4-Series will replace the 3-Series coupe. But rather than simply a derivative of the 3-Series sedan, it forms the basis in terms of both image and market perception for an entirely new series. A 4-door coupe is expected to join the 2-door, following the course set by the latest 6-Series that now is offered as a coupe, Grand Coupe and convertible.

Clearly, the new 4-Series is all about emotion, elegance, style, dynamic performance and individuality, not mere transportation. Its size, proportions, design and specifications clearly speak this language.

The Concept 4-Series Coupe is wider, longer, lower and roomier than the 2-door 3-Series. Its 110.6-in. (281.0-cm) wheelbase is 2.0 ins. (5.0 cm) longer than the 3-Series, and at 71.9ins. (182.6 cm) it is 1.7 ins. (4.4 cm) wider, which fits extremely well with a roofline that is 0.6 ins. (1.6 cm) lower.

Overall length measures 182.7 ins. (464.1 cm). The track has been expanded 1.8 ins. (4.5 cm) at the front and as much as 3.1 ins. (8.0 cm) at the rear.

The exterior design features a long, sweeping hood, with a short front overhang and a passenger compartment set well back of the front axle. The wide track and rear wheel arches, occupied by 20-in. alloy discs, send a strong message of power.

The car’s sleek and elegant design begs for a 3-door sport wagon in the tradition of a shooting brake, and BMW executives confirm they may consider such an option. A convertible is not in current plans.

Inside, there’s plenty of electronic gadgetry mixed in with the car’s wood, aluminum and leather treatments.

“The two-tone Black and Schiaparelli Brown trim provides a particularly effective showcase for the interplay of forms in the front cabin, and light-contrast stitching adds a fresh touch to the leather-covered surfaces,” the auto maker says in a statement.

Production versions, expected to reach the market in early 2013, will offer “more content, more luxury, more stance” than the 3-Series, BMW says.