The metaphor doesn't appear to make sense - at first, the new road is only "slightly wider and speed limit is fractionally higher" but then later on it appears

The metaphor doesn't appear to make sense - at first, the new road is only "slightly wider and speed limit is fractionally higher" but then later on it appears that the road needs "enough new lanes" for all the cars on the old road. I thought the premise of building the new road was because the old road's ground wasn't good enough, not that there was too much traffic and the road needed more lanes. Anyway, the whole thing hinges on the authors assertion that the new road isn't that much better, so it's really up to the informed developer/user to decide whether or not they take the new road.