Google says its new custom-built car could prevent more than half a million road deaths a year, but shouldn’t it have a steering wheel, some might ask?

Apparently not.

The company has been working on self-driving cars for several years, ­installing specialised equipment in modified conventional vehicles. These have given the person sitting in the driving seat the option of grabbing the wheel or slamming the brakes on should something go wrong.

That is becoming old hat. Its latest ­diminutive electric-powered runabout won’t have a steering wheel, accelerator pedal, or brake pedal . . . “because they don’t need them,” Google says. “Our software and sensors do all the work.”

The top speed is capped at 25mph and the prototype car can be summoned through a smartphone app. Its sensors can detect objects more than 200 metres away. Detailed maps help it to navigate the road ahead.

Inside it has two seats with seatbelts, a space for passengers’ belongings, buttons to start and stop, and a screen that shows the route — and that’s about it. Google plans to build 100 of them.

Its looks have already been derided — one pundit called it “a golf cart wearing a silly hat” — but if all goes according to plan, it could herald the biggest revolution in mass transport since the invention of the horseless carriage.

Cold calculation lies behind the ­design: the car is meant to ­appear ­unthreatening, to avoid spooking the public as technology stands poised to transform another facet of daily life.

Sebastian Thrun, the artificial intelligence guru who first led the Google car project, believes robotic cars could cut global road deaths — the biggest killer of young adults — by half, which would mean saving 600,000 lives a year.

He was inspired by the death of a childhood friend in a car crash. However, the technology is also likely to be used on the battlefield: he began by ­developing an autonomous vehicle for a competition run by the US military.

The prototypes are very basic, Google admits, and most experts believe it will take several years before its commercial production. “We want to learn from them and adapt them as quickly as possible — but they will take you where you want to go at the push of a button,” the company said.

It has been testing cars that can navigate public roads “with only occasional human intervention” in California for several years. During that time its self-steering cars have crossed the Golden Gate Bridge, cruised down Hollywood Boulevard and circled Lake Tahoe.

However, the prototype appears to fail newly introduced rules for automatic cars in California, which demand that the driver passes a special course and can take over control at any time.

Google envisages a time when chains of autonomous cars form “trains” on motorways, slashing commuting times and saving large amounts of energy.

Significant hurdles remain, however: driverless cars still struggle in situations that humans deal with intuitively – such as when traffic is being directed by a police officer around an accident. The automated cars use video cameras, radar sensors and a laser range-finder to “see” other traffic.

The project — codenamed “chauffeur” — is being championed by Sergey Brin, the billionaire Google co-founder. “It does really feel different,” he said.

“Once you take the steering wheel and the pedals out of the vehicle, it’s different to the passenger, it’s different to the software engineer, it’s a different deal. It’s a pretty big discontinuity,” he told The New York Times.