The stimulus points out a difficulty faced by automobile manufacturers two decades ago: they wanted to make more fuel-efficient vehicles, but such vehicles were lighter and less safe on high-speed highways. The manufacturers responded to this difficulty by producing two types of vehicles: a lighter one for medium-speed, local transportation, and a heavier one for long-distance travel. The stimulus concludes with a statement about the net effect of that decision: since most automobile traffic is local, this decision led to net savings in fuel use alongside no loss in safety.

To know the net effect of the manufacturers' decision to make two types of vehicles, it would be useful to know more than the manufacturers' intention in doing so. For instance, it would be helpful to know if people actually used the two types of vehicles in the intended ways. The argument assumes that since most traffic is local, most people would use the lighter, more fuel-efficient cars most of the time. But what about when these people need to travel further? It seems unlikely that most people would be willing to buy two cars and switch between them for two different types of travel. And if many people ended up using only one of these types of cars for both types of travel, this makes it seem unlikely that both fuel use was reduced and there was no safety loss: either they were using the lighter cars on the highways and running a safety risk, or they were using the heavier cars for local traffic and not reducing fuel use. So a good way to weaken this argument would be to provide information showing that people actually didn't use the two types of vehicles in the way the author assumes.