What effect can a defective steering shock absorber have on road behaviour?

A defective steering shock absorber can indeed cause the steering wheel to shimmy, which refers to excessive vibration or shaking of the steering wheel. This issue affects the vehicle's handling and control, making it more difficult for the driver to maintain stability while driving. Additionally, the overall roadworthiness of the vehicle can deteriorate due to such defects. This is crucial because according to German traffic law, all vehicles must be roadworthy to ensure safe operation on public roads.

The third option you didn't select, which states that roadworthiness only deteriorates at low speed, is misleading. In reality, a defective steering shock absorber can compromise roadworthiness at any speed, not just low speeds. Understanding the full scope of how such defects impact vehicle safety is important for compliance with traffic regulations and for ensuring the safety of all road users.