Let’s look at one of the relative newcomers to the ranks of driver assistance technology. It all started some three or four years back with commercial panel vans, like the Ford Transit and Mercedes-Benz Sprinter. Obviously, their sizeable bodies make them more susceptible to the effects of wind gusts and strong side winds, and the system originators, Ford and Mercedes-Benz, drew on existing ECU technology to provide a solution to the problems of strong winds pushing such vehicles dangerously out of lane. We’ve all experienced the same effects in our cars, (although some are more susceptible than others) and the techniques that were developed for these vans were successful enough that they are now beginning to appear on private cars.
The key to it all is the sensors used by most ECUs to measure ìyaw,î or the angular deviation of the vehicle body from the straight-ahead position, or the direction in which the vehicle is currently travelling. As we know, if you’re fighting a strong side wind your steering usually needs to be turned into the wind source to maintain a safe position on the road and stay in lane. But gusty winds and dense traffic make it more difficult and need faster reactions. Of course, existing lane assistance and lane departure warning systems, if fitted, should react in such situations, but they mostly rely on optical recognition of lane markings, where they exist, and many only give visible or vibration warnings, but take no corrective action. They also may not react as quickly as desirable.
Having recognised a situation where the vehicle is being driven off course by the wind, or maybe even a gust from a passing large HGV, the question is how appropriate automatic correction can be applied. Two main ways exist for this and earlier systems adopted use of selective braking, to cause the vehicle to pivot around the braked wheels, and effectively turn into the wind, thus maintaining a safe and correct course. This is very much the same technique as used in advanced stability control systems where, for any of a number or different reasons, such as a skid, the ECU detects directional instability, it makes a correction to maintain, or restore, stability. In this case that stability is a correct position on the road, relative to lane markings and other traffic, rather than being pushed off course. The responses, such as with the Mercedes-Benz Crosswind Assist, take into account the vehicle speed, load condition and weight distribution, as well as steering behaviour. If the driver should out-think the system and countersteer manually, the Crosswind Assist would be automatically suppressed.
Volkswagen, in their Crafter van range, has more recently adopted the alternative technology of using the steering itself to apply the correction, rather than using the brakes, possibly drawing on their considerable experience of autonomous parking. It seems, possibly, a superior approach, since no energy wastage and potential tyre wear are involved, and we could see this approach being adopted more widely. At present, on cars, the technology is confined to a number of Mercedes-Benz and smart models, and also the Renault Twingo on accounts of its shared parentage with the forfour. The Mercedes-Benz system can, however, be retro-fitted to most recent Sprinter vans. Some manufacturers may consider that advanced lane deviation warning and other assistance systems provide adequate safety, but we may expect to see more cars fitted with specific side wind assistance, which will be of particular benefit to those who regularly use motorways in areas prone to gusty conditions. Those owning leisure vehicles should note that the Mercedes-Benz-powered Hymer ML-T Motorhome is fitted as standard with the Mercedes-Benz Crosswind Assist system ñ which surely could be applied to larger bodied box vans which, when laden, are less stable in crosswinds than the panel vans for which the systems were developed.