TomTom survey reveals fastest, slowest roads in U.S.; drivers aren't speeding often

GPS device developer TomTom has published some data from its users revealing the slowest and fastest roads in the United States, plus another interesting fact: most of its drivers are staying within the speed limits.

GPS device developer TomTom has published some data from its users revealing the slowest and fastest roads in the United States, plus another interesting fact: most of its drivers are staying within the speed limits. Calculated from the data found in SpeedProfiles, TomTom's speed database, most of the recorded speeds are from drivers on interstate highways and when there isn't much traffic.

Some of the key findings:

  • Mississippi has the fastest roads, where the posted speed limits range from 65 to 70 MPH.
  • The fastest American road is I-15 through Utah and Nevada. The posted speed limit is as high as 80 MPH in some spots, with the driver average being around 77.67 MPH
  • The slowest average MPH is in Washington D.C., with averages around 46 MPH, followed by Hawaii (53 MPH), Delaware (61 MPH), Rhode Island (63 MPH), and Oregon (63 MPH).

Of course, this records people who are using TomTom devices, so perhaps that is a contributing factor in itself (listening for directions/not knowing where one is going usually slows people down). I don't know (or think) that having a GPS necessarily makes someone a more responsible driver.
I'm sure there are plenty of spots with speeding not revealed in this study. For example, given that most California highways have a maximum speed limit of 65 MPH (with a range of 55 to 70), most drivers in Los Angeles and parts of I-5 throughout the state are definitely going at speeds in the 80-90 MPH range.
What do you think about the results?