I figure RUs are here to stay, even if there isn't a direct exchange rate to credits. I may be wrong, but I am associating RUs in my head with a measure of a system's GDP. RUs giving us a way to compare the relative economies of systems despite the variety of styles of economies and variety of government types. Thereby RUs aren't a measure of monetary strength but a measure of long term wealth or investment.
In previous rule sets, we had no way of building starports or even spaceports from the ground up (so to speak). We could handwave something out of ship construction rules, but there was nothing concrete. Since we were previously using ship construction, we used credits as a measure of cost. All along I have thought that ports were a manifestation of infrastructure and therefore really are a manifestation of the ability to handle a certain volume of traffic.
From what I have seen from your responses, it seems that my thoughts on this are largely correct. Yes, Hans, there are exceptions. This is Traveller after all, and without the outliers to cause arguments over where would we be?
So, taking Rob's quicky review of a sector of data, a reasonable if small sample considering the number of sectors for which we have data, we have that the average class A is found in systems with RUs greater than 3000, the average B has around 1000, class C averages less than 600 but positive RU, D and E are found on negative RU systems.
Now, looking again at the analysis provided so far, it seems that depending on the systems previous RU situation, and therefore its previous economic strength giving an indicator of growth or decay when compared with current, we can say that some D ports are C ports that have lost some capabilities as the economy crashed or are smaller C ports that are growing to full C status as the economy continues to grow.
Similar observations can be made for C and B ports. A ports seem to be the ultimate port, and is either growing to encompass even larger capacity or is atrophying as shipping decreases and less docking space is required but is continuing to build jump capable shipping as the local infrastructure is maintaining at least one jump drive manufacturing plant.
So it comes to mind that we now know at what approximate infrastructure and economic power level a port becomes available. We have a new question: How do we gauge when/how a system develops infrastructure? It shouldn't all be GM handwave. If so, what would we argue about?
Just an aside, I have put this in the T5 forum for a reason. How do we do this using as much of the T5 guidance as we can while relying on as little of previous rulesets as possible?