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The application of technology to problems can be a beautiful sight. Take a modern seven-speed automatic gearbox. This is no 1960s-style slush-pump where everything was controlled, in the loosest possible sense, by the management of various hydraulic pressures within the gearbox casing. There was just a basic set of carburettors, a distributor that adjusted timing by the use of flying bob-weights and the most basic of warm-up controls.

Today, things couldn't be more different. An automatic gearbox is heavily computerised, and there are multiple maps of gear-change points to take into account engine revs, throttle position and more. The gearbox has a real-time conversation with the engine-management system, too, to ensure the throttle is backed off a fraction of a second before the gear change takes place. Plus, it can optimise the choice of gear for the best engine revs and torque output, and match all of this to overall engine temperature and running conditions.

So when I'm abroad, I tend to rent interesting vehicles, because there's so much to learn from them. A Hummer H2 might not be the most eco-friendly thing to drive from Los Angeles to Las Vegas and back, consuming more than 96 gallons of gas, but no-one would dispute the fun. This time, though, I decided to go green. I'd heard so many things about the Toyota Prius (or "Pious" to its detractors), I had to give it a go.

After all, when it comes to technological solutions, this baby has more techno-whizz than most. Two power sources

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- one petrol and one electric - regenerative braking for charging the batteries and some mind-boggling software to drive the whole thing, knitting together the power outputs through the constantly variable-ratio automatic gearbox. You wouldn't want an Excel-style miscalculation while driving down the motorway and end up having the electric motor arguing with the petrol.

First impressions are impressive. Starting the car isn't like your usual gas burner. Press the Power button and hold it in until the fascia boots up. Then wiggle the small "gear lever" into the drive position. Still, nothing has happened and the car is silent. Press on the accelerator and the car slides away silently, except for the quiet patter noise of the tyres on the tarmac.

The petrol engine kicks in seamlessly and you get more power on demand. It's a very refined unit, and almost silent in operation, too. In fact, the air-con unit was the noisiest thing in the car. Sit in static traffic, and a smugness comes over you - no petrol is being consumed, it's silent and there's no vibration either.

Unfortunately, it's impossible to accelerate in any meaningful way without the petrol engine kicking in. The engine runs all the time you're on a motorway, except for the rare occasions when you might be doing a long downhill stretch. Go uphill, and the engine can make a weird "mooing" noise as it slides around on the infinitely variable gearbox ratios.

And then there's the crushing reality of the fuel consumption. In several thousands of miles, spread between mooching around downtown Vegas and Hollywood and then long motorway drives between the two, the average fuel consumption was 41.1mpg. I'm sorry, but a major technological application of this nature can surely do 80mpg? Or even 120mpg?

My sisters get almost 40mpg out of their Audi A2s, cars that have an aluminium spaceframe and bodywork. The A2 weighs in at 895kg. The Prius comes in at 1,325kg, and the difference is due to the stuff that's been bolted onto the Prius to make it work as a hybrid. That's nearly half a tonne of weight difference.