This point is not relevant to the author’s argument because the author is not concerned about what happens when people are speeding; instead, he discusses what happens when people spend more time on the road as a result of not speeding.

The author’s conclusion focuses only on environmental- and safety-related benefits. Even if there were other benefits, they would be irrelevant to this argument, because the author is precise in defining what his argument applies to: safety and environmental benefits only.

This doesn’t address the main focus of the argument. The author emphasizes the amount of time cars are on the road, rather than the total number of cars on the road. This also might strengthen the argument—if more cars are on the road at one time, emissions and the chance of an accident would be higher.

The author mistakenly assumes that driving faster would not increase the rate at which cars emit fumes. If cars emitted more fumes while driving fast than while driving slow, then reducing speed limits could indeed reduce the amount of emissions created and help the environment.

The author never defines a significant vs. an insignificant risk of collision. Additionally, he never states that the only way to risk collision is to spend more time on the road; instead, he states that spending more time on the road increases your risk of collision.