Keep in mind that the safety distance you have to the preceding driver increases with speed. Additionally the large speed differential between cars leads to mor

Keep in mind that the safety distance you have to the preceding driver increases with speed. Additionally the large speed differential between cars leads to more frequent lane changes, acceleration and breaking, etc. Which hinders the flow of traffic, reducing throughput. In Germany it's common to use electronic signs to limit speed when the highway is (moderately) congested to help traffic flow more smoothly, increasing throughput (typically to 100 or 120 km/h).