Comment: How good are van safety systems?

Published 02 July 2014

Picture a typical morning. You get up, walk to your van, start it up and take to the road. You’re probably aware of the fact it has fancy systems to help you out in the event of am emrgency situation, but you’ll rarely even get a hint that they exist, let alone if they work or not. That’s probably the way it should be.

After all, the only opportunity most people get to experience traction control system or ABS kicking in will be in a potentially very dangerous situation. That’s not a position you want to find yourself in when out on the road for a days work.

But what if you do need a safety system like stability control? Can you really put your faith in a collection of sensors and circuits? We joined Mercedes-Benz at Prodrive, in the West Midlands, to find out just how useful modern van safety systems can be – and to see how tricky life can be without them.

For the demonstration a trained rally driver took us out in a Mercedes-Benz Vito, which had been specially rigged to disable its ABS and stability control systems. Climbing into a van with a rally driver at the wheel is never something you’d expect to do, but his skill was necessary for the demonstration.

The driver took us through a believable scenario – you’re driving at motorway speed and – despite the fact it is illegal – you’re messing around with a mobile phone. You look up only to see a stationary truck looming into view. With no time to stop, the first reaction is to jerk the wheel and swerve around the hazard.

Skids

A picture says a thousand words!

This causes the weight of the van to shift, upsetting its balance and brining the rear out of line. With no stability control system the van loses grip at the back and it spins, at speed, potentially into a queue of cars. Or at least it would if a rally driver wasn’t there to neatly catch the slide with deft steering and perfect throttle control. He brings the van to a nice slow stop.

Next, a switch is flicked and the stability control system is back on. We simulate the same situation, however this time, to show just how capable the system is, the driver doesn’t even bother to take his foot off the accelerator when the time comes to swerve. Foot fully to the floor he yanks the wheel to the right and then immediately back to the left.

It’s hardly elegant and gentle, but there’s no denying the safety system works. Over the course of just a second or so, sensors detect the slip at each wheel and the amount of yaw, then they pre-emptively detect what would be a spin. But it doesn’t happen – instead the power cuts out and the brakes grind and judder individually.

The van doesn’t sound healthy but it does what it is told, skipping around the obstacle while pointing where the driver wants it. Each brake applies itself dozens of times per second to tug and wrestle the heavy van towards where the driver has pointed the wheel. You can hear the system working on each individual wheel - a grinding sound, accompanied by a flashing traction control light on the dash.   

All the while the driver has his foot still flat to the floor - but there's little or no response from the throttle. After what seems like a long time the system detects that things are right – the wheel is pointing forwards and there’s no skidding or slipping. Only then does it give back control of the throttle. All-in-all this has taken place over about two or three seconds. Barely enough time for a human to react. 

It’s an exciting, exhilarating demonstration of a system that we take for granted and that could be the difference between life and death. It’s not idiot proof, of course – driving as fast as possible into a bend or a wall is never going to end well – but it goes to show just how impressive modern van safety systems are. Hopefully we won't need to use them...

DSC_5822

The van only gives back power when it's back on the straight and narrow

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