The Fiat 500L Trekking is equipped with a system called Traction+ that is designed to maximise the use of the available grip in off-road conditions.

To understand how the system works, first we need to understand a little about how a differential works.

How does a differential work?

All cars are equipped with a clever bunch of gears called a differential that sit between the left and right drive-shafts in an axle.  The job of the differential is to allow each wheel to rotate at a different speed when you turn a corner – hence the name differential – and this is important because in a tight turn, the outside wheel has further to travel than the inside wheel, meaning it also has to travel faster than the inside wheel in order to complete the distance in the same time.

Torque in a vehicle’s drive-train obeys the laws of physics just like everything else, and one of the principles at work in a differential states that energy always follows the path of least resistance.

That means that if you put one wheel on super-slippery ice and the other on nice grippy tarmac, the differential will transfer all torque to the wheel on ice because that wheel’s easier to turn than the wheel that’s got all the grip on the tarmac.  Those of you that are still following all of this will by now realise that this means you just get lots of wheel-spin and the car goes nowhere, despite having one wheel with plenty of grip.

How does Traction+ work?

Traction+ works by applying the brakes to the wheel that’s spinning, and when sufficient braking force has been applied it will reach a point where it’s easier to send the torque to the other wheel instead (the one with grip).

This is the same principle that’s behind conventional traction control systems, but Traction+ takes it further by analysing available grip levels at each wheel and ensuring the one with most traction gets the bulk of the torque, as opposed to merely slowing down an already spinning wheel.

The beauty of the system is that it doesn’t require any complicated hardware, as everything that’s needed is already fitted as part of the ABS and ESC systems.  That makes it much cheaper than a full-blown four-wheel drive system, and also saves weight that would otherwise have been added by fitting extra drive-train components, thereby helping fuel economy and emissions.

Of course, it’s no substitute for a proper four-wheel-drive system since it only acts on the front wheels, but with Traction+ and all-season tyres, a 500L Trekking is likely to make it further into the gloop than you might imagine.