Theoretically, on a completely empty highway I can achieve speeds in excess of 200mph in a sufficiently powerful car. In practice, most highways will be congested, police officers will be present, the weather may be bad, etc., and I will never be able to go above an average of 60 (in rush hours of many cities, even less). To that effect my compact car is all I really need, and I am more interested in routes to and from work that will avoid congested areas instead of freeways that offer a theoretically higher speed.
Likewise, this article isn't about raw speed, it's about what is practically possible. This is an excellent guide for those interested in data plans.