<i>If that limit is 4 mph or 10 mph, I think it&#x27;s fair to charge more.</i><p>The problem is, speed limits in the US are often underposted to raise revenue and&#x2F;or give the police an excuse to stop almost any driver.  Certain studies have shown that drivers doing 4-to-10 MPH over the speed limit are among the <i>safest</i>.  The slower ones are often either not paying attention, actively obstructing traffic, or impaired.<p>I&#x27;d be more likely to accept behavior-based insurance rates if they&#x27;re based on sound traffic engineering principles rather than politics.