The smooth, safe SUV improves on a formula that brings in repeat buyers.

Luxury means different things to different people, which explains why Lexus was the top-selling prestige brand in the US last month. No surprises then that the launch of the fourth-generation RX SUV — the brand's US bestseller — has just been held in Oregon.

Explore the 2015 Lexus RX Range

This is a car built to capitalise on its American appeal … and therein is the potential problem. The suspension is either too soft in standard guise or too hard over small bumps at city speeds with active suspension fitted.

Body roll is also beyond what buyers — particularly those from European brands — will find comfortable.

It's not all bad news — an active roll-bar setup on the F Sport versions successfully ties down lateral roll. This is the model we'd buy with any of the three engine options.

When local sales start in November, the base 2.0-litre turbo engine will be fitted only in the entry Luxury but CarsGuide believes a sportier version will join the local line-up within 12 months.

The upgraded 3.5-litre V6 — either on its own in the 350 or teamed with a pair of electric motors in 450h guise — will be sold in Luxury, F Sport and Sport Luxury trim.

The improved multimedia screen runs to eight or 12.3-inch display, there is standard autonomous emergency braking and the quality of the interior materials is higher

Lexus Australia boss Sean Hanley says a smooth (rather than overtly sporting) ride is part of the RX's unique selling proposition, along with the brand's reputation for reliability and quality. Buyers plainly like what they get, as more than 60 per cent back up their first Lexus purchase with another trip to the premium Japanese dealers.

If that's the case, the RX will garner more repeat business. This fourth-generation vehicle, says chief engineer Takayuki Katsuda, is stiffer than its predecessor in the chassis and suspension, meaning there's more to entice current owners.

For them or new buyers alike, there's much to admire. The improved multimedia screen runs to eight or 12.3-inch display, there is standard autonomous emergency braking and the quality of the interior materials is higher. The stretched chassis boosts front and rear legroom by 25mm and the extra 50mm of rear headroom means even tall passengers don't brush their hair on the roof lining.

Exterior lines — there are plenty of them — are sharp edges that delineate curved surfaces. A glass strip now wraps around the rear pillar to create a "floating roof" effect. The newly acquired full-size spindle grille is still the dominant feature as Lexus looks to stamp its corporate identity on all models.

F Sport variants drop the horizontal slat inserts inside the spindle in favour of more aggressive-looking black mesh.

In the cabin, the seats are supportive, there are plenty of wood and alloy trim highlights and the finish is first-rate, even on the pre-production vehicles used for the international launch. It's Toyota-standard fit with classier coverings and vastly better audio, topped off by a 15-speaker Mark Levinson job in top-spec models.

The turbo four-cylinder is paired with a six-speed auto and has little trouble coping with the SUV's two tonnes. It will be sold here in the front-driver, with the V6 and hybrid as the all-wheel-drive trailblazers.

The V6 adds an eight-speed auto that's not quite precise when shifting up cogs, no matter which drive mode setting is employed. The hybrid is paired with a continuously variable transmission — no surprises it is the quickest but no drivetrain can be called slow.

Wind noise has been virtually eliminated. Ironically the quiet cabin tends to exaggerate the roar from the 20-inch tyres that will be standard on F Sport and Sport Luxury models.

Final local spec and pricing are still being sorted

The steering is light and goes where it's pointed without providing much in the way of feedback and there's still the lack of rear three-quarter vision. F Sport and Sport Luxury models here will have a panoramic view camera.

Final local spec and pricing are still being sorted so we can't yet confirm whether the surround-view vision will be part of the Luxury spec.

The Safety System+ pack, standard across the range, has autonomous emergency braking, lane departure warning and active cruise control — the linked lane-keeping assist steers the car back into its lane should it veer off course.

Other confirmed inclusions extend to blind-spot monitoring, front and rear parking sensors and a rear cross-traffic alert. It's a comprehensive suite of driver aids often found as options on the RX's rivals.