Dear Mahatma: The following discussion was had as we drove on Interstate 40, and no one in the vehicle could say for sure what the law is on the subject. We seek clarification. Would I be correct in believing my Ford F-250 pickup is treated like a car when it comes to the speed on Interstate 40 and I can travel at the upper speed of 75? But would I then be considered a truck when I have my 30-foot travel trailer attached and need to reduce my speed to 70 mph? Thomas