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Mercedes-Benz Trailer Stability Assist (TSA): Trailer towing made safe




Driving with a trailer is set to become safer thanks to Trailer Stability Assist from Mercedes-Benz. The new system is able to detect the dreaded fishtailing quickly and take corrective action. This extra safety function has its roots in the ESP® Electronic Stability Program.
A trailer swerving from side to side can quickly upset the car/trailer combination. Fishtailing is the term given to this oscillating motion about the vehicle's vertical axis which, depending on the current operating conditions, can build up to reach a critical level where car and trailer can no longer be brought under control – the outfit enters a skid which can result in a serious accident.

This makes it all the more important to detect this oscillating motion as early as possible and counteract it. In future, TSA will improve handling stability when towing a trailer with a Mercedes-Benz vehicle. The new system eliminates fishtailing quickly and effectively.

TSA is an extra function of the ESP® Electronic Stability Program and shares its sensory system. Using the yaw rate sensor, TSA is able to detect movement around the vehicle's vertical axis and take appropriate countermeasures: the oscillating motion is actively stifled by applying the brakes at the front left and right wheels individually and alternately. In the majority of cases, this is sufficient to eliminate the weaving motion completely, and with it the threat of danger. If the snaking motion is particularly severe, however, the engine's torque will also be throttled and the towing vehicle's brakes applied at all four wheels to bring the speed below the critical range as quickly as possible.

Sensitive, two-stage operation

The fact that Mercedes-Benz Trailer Stability Assist operates sensitively and in two stages represents a dual benefit: TSA counters oscillating motion at an incipient stage before it becomes critical and is often able to bring it under control merely by means of gentle, corrective brake applications at the front wheels. TSA will only adjust the vehicle's speed if additional braking is imperative for stabilising vehicle and trailer – the result is added comfort for driver and passengers alike.

The ESP® warning lamp in the dashboard lights up to inform the driver when TSA takes corrective action. Incidentally, the ESP® system continues to take priority, meaning that its corrective brake commands can override those of TSA at any time. ESP® must of course be switched on for TSA to take action.

TSA will make its debut in the W 221-series Mercedes-Benz S-Class. It will be added to the specification of the M-Class from late August 2005 and will be made available for further model series successively after that.



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