A city replaced several downtown intersections with roundabouts. Traffic engineers measured a 25 percent drop in collision rates but only a 5 percent decrease in average travel time.
Which inference best explains these results?
- Drivers become confused by roundabouts, causing extensive delays that offset safety benefits.
- Roundabouts improve safety by moderating vehicle speeds without greatly affecting travel time. (correct answer)
- Most collisions were caused by pedestrians who now avoid the roundabout areas.
- Travel time decreased minimally because drivers detoured to avoid unfamiliar roundabouts.
Explanation: When you encounter reading questions about cause-and-effect relationships in data, focus on finding explanations that account for all the observed results, not just one piece of information. The key evidence here is the combination of outcomes: a significant 25% drop in collisions paired with only a modest 5% decrease in travel time. The correct explanation must address why safety improved dramatically while travel efficiency remained relatively unchanged. Choice B correctly identifies that roundabouts moderate vehicle speeds, which explains both results perfectly. Slower speeds reduce collision severity and frequency (explaining the 25% safety improvement), but don't dramatically speed up traffic flow (explaining why travel time only improved by 5%). This matches the real-world function of roundabouts. Choice A contradicts the data by suggesting "extensive delays" when travel time actually decreased. If confusion caused major delays, travel time would increase, not decrease. Choice C focuses only on pedestrians and collisions, completely ignoring the travel time data. Additionally, it makes an unsupported assumption about pedestrian behavior that isn't mentioned in the passage. Choice D suggests drivers are avoiding roundabouts entirely, which would mean the traffic engineers wouldn't be measuring the same intersections anymore. This doesn't explain how the same intersections could show both improved safety and maintained efficiency. Strategy tip: On inference questions with multiple data points, eliminate answers that only explain part of the evidence. The correct answer should account for all the results presented, not just cherry-pick one statistic.