Passage Summary: Accidents were rising until a speed limit was introduced a decade ago. Since then, accidents have stayed lower than that peak, so the speed limit must be the reason for the drop.

Conclusion: The implementation of the 90 kph speed limit caused the highway accident rate to drop by at least 15 percent.

Reasoning: Accident rates were increasing and peaked right before the speed limit was introduced, and they have remained at least 15 percent lower than that peak ever since.

Analysis: This argument falls into the classic trap of assuming that because one event followed another, the first event caused the second. To weaken this causal claim, we should look for an alternative explanation for the decrease in accidents. Perhaps vehicle safety technology improved significantly ten years ago, or maybe the 'peak' year was an extreme statistical anomaly caused by a severe winter. Any factor that suggests the decline would have happened regardless of the speed limit will undermine the conclusion.