Towing Speed

Unfortunately some of those speed limits are pretty laughable. I don’t think I’ve ever seen anyone tow at 55 in VA for example. I prefer saving fuel and towing at 60-62 but I’ll choose safety over economy. If I’m holding up traffic that is more stressful and unsafe than just driving at 65-67 closer to the normal flow of traffic in the right lane. Frequently there is no good alternative route, uncontrolled access two lane highways are much less safe than the interstates if there is significant traffic.

Say you're towing at 60. You aren't unsafe in one state that happens to have a 55 mph limit and then miraculously achieve safety when you cross the state line where the limit is 65. I acknowledge that you would most certainly lose a lawsuit though.

Traffic engineers are the ones who usually set the speed limits based upon their agreed upon criteria.  See for example:  https://www.ite.org/technical-resources/topics/speed-management-for-safety/setting-speed-limits/  Generally, they use the 85th percentile approach which says the speed limit should be set within 5 mph, plus or minus, of the 85th percentile speed, as measured on the road.  That speed is adjusted in recognition of other road characteristics, such as alignment, parking activity, pedestrian movement, residential and commercial activity, and other factors affecting safety.

It's not so clear in VA.  Read the rule:  https://law.lis.virginia.gov/vacode/title46.2/chapter8/section46.2-870/  The only place where there is a speed limit of 70 is on a very select few highways meeting the criteria in the statute.  The rest of the time it is substantially lower, and even more so for trucks and trailer towing vehicles.  Technically it appears that trucks can go 70 on designated highways, but it appears it's legislature has ignored the reasoning that it used for having a truck speed limit lower everywhere else, probably as a result of the trucking industry lobby.  And, that 70 speed limit is tempered by the basic speed law adopted in VA.  http://www.virginiadot.org/info/faq-speedlimits.asp  So if there are any conditions that justify a lower maximum speed, you can't go 70.  You must slow down to a "reasonable" speed for the circumstances.