Volvo Cruise Control a test of nerve

Volvo S60. Photo / Supplied

Richard Livock pulled out of Volvo's main office in the new S60 sedan and headed for the motorway on-ramp at Greenlane.

It was late in the day, traffic was at its peak and Livock was headed home across the Auckland Harbour Bridge.

It was a trip he'd made hundreds of times. But this one would be different: he was trying to drive 12km in bumper-to-bumper traffic without using the car's brake or accelerator.

Volvo NZ's national service manager had switched on the S60's Active Cruise Control, an optional package of watchdog electronic gizmos that includes City Safety, and, when all things are equal, allows the driver to focus only on steering the car. It's basically a radar unit, keeping the S60 at a safe distance from the vehicle ahead and watching what those at either side are up to. Bit like KiTT from the television series Knight Rider.

In this case, Livock programmed the system to slow and stop the S60 within 10m from the car in front.

"To be honest, it gets a bit dodgy at traffic lights, coming up behind a line of cars," he said. "It's hard not to stop your foot from hovering over the brake pedal. There are some ballsy moments - but the system will do it."

Four electronic bars on the S60's instrument panel point to the programmed stopping distance. One bar is 10m, four bars is a maximum 40m.

"I could have set it to four bars, but drivers on the motorway will inevitably pull across in front of you to close up the gap," he said. "Setting it at one bar stops people pushing in."

If the Volvo is stationary for less than three seconds, electronics step on the gas to get it moving again. Any longer - at lights, for instance - and the system goes into standby. Cue the driver's right foot to get it moving again.

Same to stop the car, if the S60 is at the head of a line of traffic with nothing in front for the radar to lock on to. (That said, tests have been done with software that responds to traffic lights.)

Optional ACC is central to Volvo's most ambitious aim: preventing any crash deaths in a Volvo by 2020.