If, like me, you find yourself dismissing some of the ‘green’ breakthroughs claimed by the motoring industry, then sit up.

Here’s one that you shouldn’t ignore.

And, like most good ideas, it’s incredibly simple. Basically, it involves switching off the engine when it’s not doing anything, like at traffic lights or in queues.

It’s so simple, there’s bound to be a flaw in it somewhere, but to be honest I haven’t found it.

And the positive results are staggering. This model normally returns 49.6mpg around town. With this system in place, it rises to 57.7mpg.

On a run, it will do 74.3mpg and with the system working that rises to 83.1mpg.

And fuel emissions are slashed, too, from 119g/km to 104.

That’s great for most people, but for high-mileage company car types, savings like this can be very significant.

It’s so simple yet so effective. In fact, the only drawback is that you’re forever thinking you’ve stalled the car at junctions.

The V50 is a car which deserves a far higher profile. Since the introduction of the C30 three-door hatch back, the company’s S40 saloon and its sister V50 estate are no longer the babies in the Swedish manufacturer’s line-up.

It is a label that they fully deserve to lose, as you would be hard pushed to find two more grown-up cars, and the arrival of this green DRIVe version makes it even more attractive.

The V50 estate is a fine example of a car designed and built by mature minds, for sensible owners. The grown-up ethos is evident even before getting into the car. The key fob, although chunky and at first sight a bit Eighties, is a triumph in design.

Firstly, the buttons are big and obvious. There’s no unlock button integrated stylishly into a badge or fiddly little switch hidden about the fob. Instead, you get five big and clearly marked squares: one to unlock, one to lock, one to open the boot, one to switch on the lights and a panic button to trigger the alarm.

It may not sound like much, but you’ll appreciate the hassle-free design as you stumble back through a wet car park, arms weighed down by shopping bags, children, or both, blindly fumbling at the fob.

It doesn’t end there either. Inside the car, the ignition barrel is located in clear view on the dash. Not on the steering column and obscured by the wheel, and it starts without even a hint of ‘clutch in, turn key, push starter button’ shenanigans.

Finally, before I put the key appreciation to rest, the fob is completely plastic, meaning the area around the ignition barrel and door handles will not end up as scarred and gouged as a gladiator’s knuckles within weeks.

From the comfy driver’s seat, the V50 interior is refreshingly uncluttered. As organised as an accountant’s desk, all of the audio and climate controls are integrated into a stylish floating centre console, with a trinket tray located behind it. The super-efficient and suitably Swedish layout does have it’s drawbacks: some of the buttons are quite small and the gear lever can get in the way of those nearer the bottom, but for intelligent use of space delivered in a stylish package, it’s first rate.

Of course, it’s up to the owners to make the best use of the space in the rear, but they can rest assured there’s plenty of it. The back will seat three adults comfortably, with admirable head and legroom. Fold the rear seats flat and there’s more than 1,300-litres of space combined with a deliberately low, wide and flat opening and floor to make loading big items easy.

Should you find yourself with a boot-full of washing machine, this car will still perform. It’s a big car for a 1.6 litre engine but it rides and handles very well.

Volvo offers an impressive array of petrol and diesel power in the V50, but this engine – small for such a big car – is arguably the most sensible option.

The V50 drives like a grown-up car. It has sure-footed handling and gives the impression that it would remain perfectly composed right up to the limit. The ride is ideal for A-roads and the motorway, but the compact estate doesn’t feel out of place on a twisty B-road, thanks to the responses through the large steering wheel.

The V50 wouldn’t be a Volvo estate without a huge list of safety features, and as usual the model has all bases covered. A multitude of airbags, intelligent braking, whiplash protection and Volvo’s Intelligent Driver Information System – which prevents non-essential interruption from the car’s displays or phones where fitted during complicated manoeuvres – comes as standard.

The shell of the V50 crumples and deforms in all the right places inng an accident, and even pedestrians are catered for with an energy-absorbing front end. Door mirrors with better rear visibility have been added, while the ability to turn the lights on from the key fob adds another practical feather to the V50’s hat.

For the extra safety-conscious, additional equipment such as Volvo’s Blind Spot Information System can be specified, and the addition of the Family Pack will bring built-in child booster seats in the rear. The V50 is certainly never going to endanger Volvo’s reputation for safety.

The model’s trump card, however, is that it manages to be sensible and appealing in equal measure. It is as good to look at as any German super-estate. The boxy Volvo shape is reassuringly traditional and level-headed, but the subtly flared arches, gentle slope of the bonnet and broad shoulders give it a dynamic and sporty presence. It’s accentuated on the Sport model by a meaty body-kit, big alloys and rear spoiler.

It might be as practical as a pair of plain pyjamas, but this is not a car that will mark you out as safe, sensible or boring. The best part of being grown up is that you get to play by your own rules every now and again.

PRICE: £21,745 on the road. The range starts at £16,995.

ENGINE: A 1560cc diesel engine generating 109PS.

PERFORMANCE: Top speed 118mph and 0 to 60mph in 10.9 seconds.

COSTS: Urban 57.7mpg; extra-urban 83.1mpg; combined 72.4mpg.

EMISSIONS: 104g/km.

INSURANCE: Group 8E.

WARRANTY: Three years, 60,000 miles.