...however the few people that DO [pay attention to speed limits] cause accidents because it makes the differential speed much higher.
It's just an abstract that we're discussing here, I know, but the abstract absolutely, categorically does not say that. At all. You're guessing that's what it means.
Sorry, that is from the article (the OP), not the paper that was linked to. The article states that the 10% of people who actually pay attention to the speed limit increase the differential between speeds of cars when the speed limit is too slow.
It's just an abstract that we're discussing here, I know, but the abstract absolutely, categorically does not say that. At all. You're guessing that's what it means.