As evidenced by the fatality statistics. But we can easily drill into the statistics. NY state had a 4% compliance with the 55 mph speed limit on rural highways before the speed limit was raised. That means 96% were speeding. Traffic safety engineers like a 85% compliance. Low compliance means that there is a big spread in speeds which causes more accidents. There is no way to tell what fatalities would have been if everyone complied, but we can estimate they would be lower. But how do you do that, and should you try to make 96% of the drivers criminals? When the speed limits were raised, fatalities kept falling, like those that believed they would. The IIHS was completely wrong on its increase of fatalities, but the raised limits reduced the percent of speeders. A more appropriate level allows for lower number of officers enforcing the law, and fewer breaking the law. States instead of the federal government have the power to set the speed limits. Think of it this way. If we enforced with tattlers a 10mph speed limit traffic fatalities would drastically fall, but the great majority would have their rights removed. There should be a happy medium of enforceable speed limits that people follow. 55 was completely arbitrary.