Phantom Roads and Railroads

[samson]

I don't know if this tactic is well-known or not. But it is consistent and quite exploitable.


The existence of a road or railroad between the Source and Destination cities of a Trade Route increases the value of that Trade Route by 50% or 100% respectively. Surprisingly, the road/railroad does not actually have to be complete in order for the Trade Route to receive this bonus.

If a city belonging to the same civ as the Source city exists along the qualified route between the Source and Destination city, the road/railroad needs only extend as far as the interposed city to earn the bonus. Apparently, the algorithm that checks for a qualified road/railroad route stops as soon as a city is encountered and never checks the remainder of the route to the Destination City.

This means that an SSC can reap the full benefit of road/railroad bonuses on its trade routes to a far-off foreign megalopolis by building a road/rail connection to a local 'station' a mere 2 or 3 squares away. The 'station' must be located along the qualified path between the two cities. This location can be found by using to GOTO command to send a settler to the remote city and then terminating its travel just outside the SSC's city radius and founding a new city. When the road/rail is complete to the 'station', the full bonus will apply on trade routes to the foreign city.

This tactic not only allows road/rail bonuses to be attained quickly and with much less effort, but also makes the trade route bonus less vulnerable to disruption by non-allied units or pillagers. Foreign troops interposed on the 'phantom' portion of the road/rail have no effect on the trade route.

Trade route bonuses achieved in this way still suffer from other limitations of the road/rail bonus. For example, the trading cities can still be no more than 22 squares apart and they cannot cross the '0' meridian.

This tactic will affect only the Source city's trade route. To obtain the bonuses for the Destination city, a second 'station' must be built near it along the reverse qualified route. It is also this 'return route' which is used in Caravan Delivery Bonus calculations.

[debeest]

Samson, this information has been available for some time, requiring only that some almost obvious conclusions be drawn, and I'm sure the really good players have been exploiting it -- but from the rest of us who play instead of thinking, thank you for yet another insight.

Your last sentence puzzles me, though. For the delivery bonus, my understanding is that the route is unimportant; what matters is the distance, as calculated by Civ's odd methodology. Am I missing something?

[Scouse Gits]

samson - I have noticed that some cities have a better than average trade route, when no transport link exists. Thanks for clarifying our thinking with the notion of the station. (If you can post a map with an example that would be helpful to many of us)

The rule of 22 squares - that means that no benefit can be obtained from any transport link greater than this distance? If so 22 seems a strange number ... any thoughts?

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SG(2)

[solo]

I will certainly look forward to using this exploit, but have two questions about it.

Can the road route connecting the "station" to the Destination city meander around, or must it also be along the optimal GOTO path?

Also, will connecting this road to other Destination cities affect the railroad bonus for the Source city?

[Straybow]

Hmmmm, I, too, had never considered this ramification of GoTo checking. Since you may want "feeder" cities in any case…

Solo, no route connecting the intervening city to the Destination is necessary for Source city road/RR bonus. The algorithm stops and doesn't check the remainder of the route. Only the GoTo route from the Source to the Destination has any effect on that trade route value to the Source city.

[Thoddy]

There is another thread about this topic in the stratgy forum "Trade??"

http://apolyton.net/forums/showthread.php?s=&threadid=52337&pagenumber=2

there is a attached file at my post from 13.06.2002
cab4000.sav

[samson]

debeest -

Your last sentence puzzles me, though. For the delivery bonus, my understanding is that the route is unimportant; what matters is the distance, as calculated by Civ's odd methodology. Am I missing something?

Yes. The Delivery Payment has a variety of bonuses that can increase the base payment, among then a Road (50%) and Railroad (100%) bonus. What I'm saying here is that the route required for the Delivery Payment bonuses is the return route (the Destination-to-Source road) and not the Source-to-Destination route which the Trade Route bonus requires. For further information, see my post 'Calculating Caravan Delivery Payments'.

Solo -

Can the road route connecting the "station" to the Destination city meander around, or must it also be along the optimal GOTO path?

No, it can't meander, it must follow the optimal GOTO path.

To clarify, for the Source City to receive the road/railroad trade route bonus, it needs connection to a station on the Source-to-Destination route. For the Destination City to receive the trade route bonus, it needs connection to a station on the Destination-to-Source path. Most often these two routes are different. The onetime Delivery Payment road/railroad bonus depends on the Destination-to-Source route.

Also, will connecting this road to other Destination cities affect the railroad bonus for the Source city?

What do you mean by 'this road'?

Thoddy -

In your referenced post, you state:

Yes, it seems so, that building roads on the opt. path outside the city radius is not neccessary.

This is not exactly correct. Merely building roads within the city radius is insufficient. The road must connect to one of your own cities which lies on the optimal path to the Destination City. If the interposed city lies well outside the city radius the road has to be built all the way to it.

SG2 -

The rule of 22 squares - that means that no benefit can be obtained from any transport link greater than this distance? If so 22 seems a strange number ... any thoughts?

Correct. The 22 squares rule means than no Road or Railroad bonuses can be obtained if the two cities are more than 22 movement squares apart, no matter what route is involved. Two cities 22 squares apart connected by Railroad in a direct E-W line receive the 100% railroad bonus. If they are 23 squares apart, they do not.

I agree that it is a strange number and it is not the same as a 'distance' of 22. Distance in Civ2 (as measured by the rectangle method or the formula I posted under 'Caravan Delivery Payments') counts distance in the E-W and N-S direction as 1.5 and NW/NE/SW/SE direction as 1. But the 22 squares rule is based on 22 movement points.

I'm sure you're right about receiving the 'phantom road' bonus often in game play and not recognizing why the route is greater than expected.

In the attached picture, the newly founded city of Atlanta is a 'station' for Washington. It lies on the GOTO path from Washington to Paris, from Washington to Orleans and even on the Washington to London path. In Washington, trade routes to any of these cities will receive a 50% Road bonus by virtue of the short road from Washingon to Atlanta.

[Scouse Gits]

samson That's helpful and clear for all to see. Great attention to detail

As the GOTO path is so critical explorers take on a new meaning!

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SG(2)

[solo]

My question was about the railroad bonus, but I forgot to mention that. I was thinking that the railroad only had to go to the station, but that a road from the station to the Destination city was also needed to get the railroad Trade Route bonus.

If I was wrong, then can I assume that just a railroad to the station is enough for the railroad trade route bonus?

Also, if I want the delivery bonus, too, am I right that any station on the GOTO path railed to the Destination City, will be enough for that bonus?

[debeest]

Samson,

"Yes. The Delivery Payment has a variety of bonuses that can increase the base payment, among then a Road (50%) and Railroad (100%) bonus."

D-oh!! I knew that, of course. I'm such an idiot.

So I gather that the answer to Solo's last question is, any station on the GOTO path FROM the destination city will get you the delivery bonus. But I gather, from the above, that that station has to be a city of the DESTINATION city's civ, right?

[samson]

Solo,

The Railroad and Road bonuses work just the same. You only need a railroad to the station to get 100% bonus, no road needed all the way to the destination.

For the delivery bonus, a railroad is needed between the Destination City and a station near it on the GOTO path originating at the the Destination City (i.e. the path that a unit stationed in the DC would take to the SC if given the GOTO command.)

[solo]

Thanks, it's crystal clear now. What a bargain!

[Straybow]

When the algorithm checks the Source-to-Dest path, any unit or city from a foreign civ on the path kills the road/RR bonus. What about checking the Dest-to-Source path for delivery bonus?

[Thoddy]

Originally posted by samson

In the attached picture, the newly founded city of Atlanta is a 'station' for Washington. It lies on the GOTO path from Washington to Paris, from Washington to Orleans and even on the Washington to London path. In Washington, trade routes to any of these cities will receive a 50% Road bonus by virtue of the short road from Washingon to Atlanta.

Little question: did you also check the (road) bonus with the same configuration but without Atlanta.

If I remember right from the other test, you have to build a road at the Atlantasquare to get the bonus.
Sorry but I have not the time to check this by myself.

But overall excellent work Samson.

Little suggestion:
by blocking the optimal path, some cities could fall into civil disorder immediately losing their trade bonuses. Much cheaper for bribing.

[samson]

Straybow -

When the algorithm checks the Source-to-Dest path, any unit or city from a foreign civ on the path kills the road/RR bonus. What about checking the Dest-to-Source path for delivery bonus?

First, it isn't all foreign units that kill the road/RR bonus, it's only units of non-allied civs. Your allies can camp all over the road/RR and not effect the bonus.

And remember, even non-allied units kill the bonus only when they are on the portion of the path with road/RR (between the Source and station). They do not effect the bonus if they are on the unroaded part of the 'path'.

For example. in the picture posted above, Washington obtains the Road Bonus on a trade route to Orleans even though the French are not allies and the garrison troops in Paris block the 'path' to Orleans.

Second, yes. The road/RR delivery payment bonus is also lost if non-allied units are on the Dest-to-Source road/RR.


Thoddy -

Little question: did you also check the (road) bonus with the same configuration but without Atlanta.

Yes, I checked. A city is required, a road/RR alone does not provide the bonus.

If I remember right from the other test, you have to build a road at the Atlantasquare to get the bonus.

No. That's not correct. Atlanta could be built on the tundra one square closer to Washington and it's current location left unroaded, the bonus would still be obtained. Alternatively, if Atlanta is moved closer to Paris, the road must be extended beyond it's current location to connect to the city's new location for the bonus to be obtained.

I have loaded the save you posted from your previous testing and have found nothing in it to suggest that roads alone (without connection to a city) provide the road/RR bonus. All your data seems to confirm my interpretation.