Expected Ship Traffic (S=Ix/H)

[Levi]

Am I just goofing up the math, or is this right?

So, I've been looking at the worlds associated with my patents of nobility and considering how a noble would develop them. Both (Dreva in Mass, and Mushinag in Deneb) are importance -2 worlds.

The expected traffic at -2 is beyond abysmal. If I'm doing the math right, it looks like just about one free trader every 100 years. S=10^-2/100=1per 10,000 weeks, 10,000/52= 1per 192 years, figure a small trader might only have 50 dTons of cargo hold so half that time.

I can't see how that could be correct though, if a ship with news of the Imperium or trade is a once in two lifetimes event people would forget that there even was an empire and the nobles would have no way to communicate with their liege lords, assuming they even knew who they were.

Did I mess up my order of operations, or is the first task of these nobles to subsidize a monthly ship?

 

[Draconian]

Yes, I had a look at that equation and it doesn't seem right.

The exponential nature of it is a bit severe. It should be something based on population and, admittedly, something to do with whether it's on a major space route or not.

 

[robject]

If I recall, that equation is for scheduled, and perhaps only scheduled and profit-motive-based, transports. Unscheduled, and perhaps even subsidized ships, are not included in that number.

 

[esampson]

I think the formula needs to be reworked. I've been trying to find ways to 'nudge' the formula but the problem is that it has that 10^x in it.

Using Spinward Marches as an example the highest importance within the marches is a 5. That works out to 100 1000 ton ships per week or about 14 per day. Now at first blush that might seem correct but there's several issues with it.

First, 14 per day would be pretty low traffic considering the size of the spaceport and all its facilities. Class A starports seem to be almost small cities. One ship with a few dozen people landing every hour and a half just isn't going to support that. And for those people who think that it is unreasonable to handle many more flights than that Hong Kong International handles roughly 1000 planes per day, nearly two orders of magnitude more. And that is with Earth level technology.

This isn't to say that the amount of space traffic should be equal to what HKI handles. Simply that it could be. Traffic handling is not the consideration.

The second issue with that number is that this is the highest importance within the marches. You have a system with a single point lower, such as Regina, the sector capital, and you're looking at 1.4 ships per day. Drop to an importance of 3 and it is a ship per week (or 1.4 smaller ships per day). Below a 3 and it is a ship per week and they are all smaller.

Incidentally, 88% of all systems within the Marches are below a 3. It doesn't seem possible for any but the simplest (E) starports to remain operating on 1 ship a week or less.

Grinding a few numbers, making a few educated guesses (I assume that somewhere out there is probably a system with an importance 2 points higher than the maximum seen in the Marches), and trying to keep a geometric curve I would change the formula to 35000x2^i tons of cargo arriving per week.

That gives the highest systems in the Marches about 160 large vessels per day, which is definitely within what could be managed and with an Earth sized population is about 27 grams per person. Perhaps a little high, but these are the busiest systems in the sector. Regina would get about 80 such ships per day and those systems with a 3 would see around 40 ships per day.

 

[Murdoc]

Thank you, that certainly does seem more reasonable to me, although even 160 doesn't seem that high to me, since that would amount to about 6 ships per hour, or about 1 every 10 minutes. Given size and automation abilities, I could easily see 10 times that, or even 100. Especially given this:

Class A starports seem to be almost small cities.

I don't know about that, but I seem to recall the idea that a planet can have more than one starport, especially big planets, so that would increase their capacity even more, and that's not including even more spaceports for in-system travel. I know that that is not a direct influence on inter-system travel, but it does mean that the starports needn't be burdened with in-system travel craft.

 

[Bloo]

Using Spinward Marches as an example the highest importance within the marches is a 5. That works out to 100 1000 ton ships per week or about 14 per day. Now at first blush that might seem correct but there's several issues with it.

By way of contrast, using the GT:Far Trader formula for Jewell results in 125,100 - 310,500 displacement tons/week (31GigaCr - 125 GigaCr/year) with destinations or origins in Jewell (Mongo, Ruby, Emerald, Lysen, Nakege, and Esalin).

Glisten <--> Aki traffic would be the same, just between those two systems.

 

[esampson]

By way of contrast, using the GT:Far Trader formula for Jewell results in 125,100 - 310,500 displacement tons/week (31GigaCr - 125 GigaCr/year) with destinations or origins in Jewell (Mongo, Ruby, Emerald, Lysen, Nakege, and Esalin).

Glisten <--> Aki traffic would be the same, just between those two systems.

So I'm at least in the same neighborhood as your original formula. That's good.

Oh, one other thing I meant to add. Obviously people have different visions for exactly how much trade there is. If my formula isn't agreeing with your totals you might want to try changing that first number (the 3500) while leaving the rest of the formula the same. A small tweak down would result in 128 ships per day, which is obviously a very convenient number since the total doubles or halves at each level and a slightly larger tweak up would result in 256 ships, which is also a good number for the exact same reasons.

 

[robject]

I like the index being a power of 10 -- that's in line with the world size and pop digit, and doesn't nail the actual number down further. I like that.

If Regina is Importance +5 (Starport A, TL C, Ag, Ri, Both Bases), then expected traffic is in the hundreds.

I think the text should be clear that this is a range, i.e. in this case, from 100 to 999 ships per week.

Still might be too low for some, but I like it a lot better than 100 ships per week.

 

[esampson]

World size isn't in powers of 10. It is a straight 1600 km of diameter for each world size. Hydrographics is also a straight 10% per digit. In fact population is the only one that is definitely in powers of 10. Atmosphere is unclear but definitely not in powers of 10 (or else a 5 might as well be a vacuum) and government and law level are too abstract for any kind of argument about arithmetic or geometric progressions.

Regina also only has an importance of 4 (which is odd to me, but that's a separate issue) which would mean it would see about 10 ships per week under the current formula, not hundreds. Meanwhile my hypothesized I7 planet sees 1428 ships every single day (which is do-able, but if there is ever an I8 planet they would probably be crushed by the 14,286 ships coming in.

And of course 88% of the Spinward Marches would see only 1 ship per week or less.

 

[esampson]

Since I've got this wonderful spreadsheet of the Marches I thought I would run a few numbers and see how that works out. This is what I came up with.

Importance	Systems	Frequency
5	7	every 10 minutes
4	9	every hour and a half
3	15	every 17 hours
2	23	every week
1	45	every 2 months
0	43	every 2 years
-1	45	every 2 decades
-2	43	every 2 centuries
-3	42	every 2 millennium

So on 30% of the systems in the Spinward Marches the population would probably have never seen a space ship. On 63% it would be so uncommon as to probably be a cause for a major celebration. This are 100 cargo ton ships, by the way, not the large 1000 cargo ton ships.

Certainly a campaign could be built with such an environment but under such conditions the players arrival would be a huge event an awful lot of the time.

You could stay with a power of ten system but your base needs to be much, much higher and at that point the number of ships in the air around planets like Regina are going to be huge (which is actually realistic, but the numbers will be so large there's almost no point in having them other than perhaps for planetary economy calculations).

 

[Bloo]

So I'm at least in the same neighborhood as your original formula. That's good.

Oh, one other thing I meant to add. Obviously people have different visions for exactly how much trade there is. If my formula isn't agreeing with your totals you might want to try changing that first number (the 3500) while leaving the rest of the formula the same. A small tweak down would result in 128 ships per day, which is obviously a very convenient number since the total doubles or halves at each level and a slightly larger tweak up would result in 256 ships, which is also a good number for the exact same reasons.

I did some numbers but for Glisten. There are 26 systems within 5 parsecs. Totaling the volume of trade that has Glisten as a destination or origin (ignoring through traffic, which could be very, very substantial) using the GT:FT stuff:

Annual $ of trade: 364 Billion Cr to 1,467 Billion Cr.
Displacement tons/week: 1,465,000 to 3,635,000

At peak ships/day
At 1000 tons of cargo per ship: 519
At 3500 tons of cargo per ship: 148

Through traffic is also likely to be substantial. At a glance, I'd estimate another million displacement tons/week at peak.

Now, try rationalizing that much traffic in systems with lower level star ports.

Side note: assuming peace enough that trade is allowed with the Zhodani. Glisten would have 500 to 1000 tons of weekly cargo with several different systems in Chronor subsector. And 5,000 to 10,000 with Jewell. And heck, Glisten has as much trade with Mora as it does with Aki.

 

[rancke]

I did some numbers but for Glisten. There are 26 systems within 5 parsecs. Totaling the volume of trade that has Glisten as a destination or origin (ignoring through traffic, which could be very, very substantial) using the GT:FT stuff:

Annual $ of trade: 364 Billion Cr to 1,467 Billion Cr.
Displacement tons/week: 1,465,000 to 3,635,000

Assuming the average of the two figures, that amounts to 0.0003 dT per inhabitant.

At peak ships/day
At 1000 tons of cargo per ship: 519
At 3500 tons of cargo per ship: 148

Some of the ships will be megafreighters, which will cut down on the number.

OTOH, you haven't accounted for passengers, have you?

Side note: assuming peace enough that trade is allowed with the Zhodani. Glisten would have 500 to 1000 tons of weekly cargo with several different systems in Chronor subsector. And 5,000 to 10,000 with Jewell. And heck, Glisten has as much trade with Mora as it does with Aki.

Yeah, FT has the problem that you have to sum up a substantial number of individual trade pairs to get a world's trade volume. It's one of those ideas that sounds good, but turns out to be a pain to implement.

I'd rather start with the population and calculate the size of the export based on that, modified by trade classifications and starport type.


Hans

 

[Bloo]

Some of the ships will be megafreighters, which will cut down on the number.

Yep. And GT:FT assumes that predictable, high value trade routes will be pretty much dominated by well-capitalized rational actors. So actually, almost all of that would be whatever the interstellar equivalent of the Maersk EEE class Mærsk Mc-Kinney Møller in your TU (which has about 36,000 traveller displacement tons for cargo available - about the same as 20 Leviathans).

OTOH, you haven't accounted for passengers, have you?

Right. For the Glisten example above, the passenger traffic range would be:
1,465,000 to 3,635,000 million/year. Just from/to the nearest 5 parsecs.

Yeah, FT has the problem that you have to sum up a substantial number of individual trade pairs to get a world's trade volume. It's one of those ideas that sounds good, but turns out to be a pain to implement.

Gravity model of trade economics.
Difficulty of implementation depends entirely for what you're trying to model. If you just want to have a fairly scientific way to estimate the trade between System A and B, or all the Trade starting or ending in System X: pretty simple. If you want to simulate the entire Spinward Marches, that spreadsheet gets kind of big (which is what I've done because I'm a dork). Or even use the trade route building rule of thumb in estimating total trade coming to/from a system: if you have 3 of a low level, bump it up to one of the next highest level. Because of the logarithmic nature of the tables, it works out fairly similar.

I'd rather start with the population and calculate the size of the export based on that, modified by trade classifications and starport type.

That, modified by Tech Level, is essentially how you get to the World Trade Number. Population + TL is basically a Gross Domestic Product. Then starport modifier. GT:FT moves the trade classification analysis to the trade part because it generally only relevant (or mostly relevant) for trade when you're dealing with a trade partner.

I think the T5 method suffers from not looking at trade relationships, but if all you want is some way to generate the number of ships your players see in Port Foo, it's probably fine (with tweaks suggested here).

Thinking about this, I kind of feel part of the problem with Traveller in later incarnations, but more this one, is that it's more of a simulator than a game. And we tend to discuss it that way here - I'm definitely guilty of that. Many of the systems in T5 strike me as intended to be modeled in software, which is not role-playing (but is much of what I do for a living). And the popularity of the game and setting is weaker for it.

 

[pendragonman]

Try looking at # of ships arriving per day into Atlantic Ocean ports in the 1850's and 1920's for comparison. Modern comparison isn't quite right.

 

[robject]

[...]
Difficulty of implementation depends entirely for what you're trying to model. If you just want to have a fairly scientific way to estimate the trade between System A and B, or all the Trade starting or ending in System X: pretty simple. If you want to simulate the entire Spinward Marches, that spreadsheet gets kind of big (which is what I've done because I'm a dork).

[...]

I think the T5 method suffers from not looking at trade relationships, but if all you want is some way to generate the number of ships your players see in Port Foo, it's probably fine (with tweaks suggested here).

I agree with your last point.

In this particular case, difficulty of implementation depends entirely on how you model it. Take the best trade partner to your world and estimate traffic based on that pair only. Everything else won't make an order of magnitude difference. At this level of modeling, that's the best you can do anyway.

 

[rancke]

In this particular case, difficulty of implementation depends entirely on how you model it. Take the best trade partner to your world and estimate traffic based on that pair only. Everything else won't make an order of magnitude difference. At this level of modeling, that's the best you can do anyway.

The one I've been using is taking the best trade partner and doubling it. The other half covers everyone else.

Unless there are more than one best trade partner, that is.


Hans

 

[Selandia]

Try looking at # of ships arriving per day into Atlantic Ocean ports in the 1850's and 1920's for comparison. Modern comparison isn't quite right.

Good idea, lets push it.

1850's pre steam, long tricky, high number of death at sea, awfull CT low berth survival rate make sense. Long night like figures with starvation on dying world filling low berth. Economic oportunities limited, J-1 TL 9.

1870's Introduction of steam have made some high value cargos easier to move. The introduction of the compound engine will dramatically reduce cost. Compare those figure to J-2 TL 11, (while J-2 is significant, this TL is more significant for it lower the cost of J-1 engine room with Modified level tech) economic opportunities are more numerous. Trade number boosted by subsidized liners.

1885 Triple expansion engine ( steam more economical than sail on most route) the golden age of steam start. J-3, TL-12, one could reach farther for business. What was made uneconomical by 2 jumps (J-2 + J-1) and one month of operation can now be shipped in one jump.

1900's the modern large and fast liner is entering the stage. Quadruple expansion (TL 13), turbine (TL 14), combination machinery (call it TL-15, to provide Modified level to J-4) including electrical drive. Diesel yet to become significant but showing (unsure of the translation in T5 term for the purpose of this exercice).

1920's post war reconstruction and limits to US imigration crooks the figures with the depression ... depressing them at the end of the decade.

have fun

Selandia

 

[Bloo]

The one I've been using is taking the best trade partner and doubling it. The other half covers everyone else.

That works great.

 

[john_g]

Ships/ not aircraft

I think the analogy of a starport to an airport is less accurate than a starport to a seaport. when you look at seaports the numbers you are getting make more sense.

 

[Draconian]

The formula's terrible. Contact would be so infrequent in the less important worlds that it would cause linguistic drift.

"Sirrah, I am a merchaunt. Hast thou need of wares such as mine?"