Regulations Spotlight
Revised ECE Regulation Permits Electronic Steering Systems.

With the publication of Supplement 3 to ECE Regulation 79.01 on steering systems, it is now possible to gain approval for electronic steering systems (i.e. steer-by-wire systems, where there is no mechanical link between the steering wheel and the road wheels).

In traditional steering systems, the mechanical link between the road wheels and the steering wheel (particularly the steering column) has an adverse effect on occupant protection in a frontal impact, due to the transmission of crash forces via the steering column and the subsequent movement of the steering wheel. To address this issue, all modern vehicles incorporate some form of collapsing and/or energy absorbing mechanism in their steering columns. However, with an electronic steering system, it will be possible to delete the steering column, thereby removing its effect on the steering wheel movement in a frontal impact and, hence, allowing improvements in occupant protection. Furthermore, deletion of the steering column will allow left and right hand drive versions of the same vehicle to be designed and produced more easily.

The new requirements for electronic steering systems permit the steering system to be influenced by on board driver assistance functions, such as lane guidance systems and dynamic stability control systems. However, the requirements specify that the driver must always be able to override such assistance functions.

The new requirements specifically prohibit any external control of the steering system (i.e. steering control being influenced by off board signals from roadside beacons or transmitters embedded in the road surface). Also, the new requirements prohibit electronic steering systems for trailers, where the energy supply and electrical control is supplied from the towing vehicle, until suitable international standards on connectors and data exchange have been agreed.

The general requirements for electronic steering systems (steering efforts, system failure provisions, failure warnings, etc.) are identical to those applied to traditional steering systems. However, a new Annex containing "special requirements to be applied to the safety aspects of complex electronic vehicle control systems" has been added to specifically cover electronic control systems. The contents of this Annex are identical to those of Annex 18 of ECE Regulation 13.09, which was introduced to cover electronic braking systems.

Posted: June 2005 by Nick Bowyer