I'm mentioning this because if we're talking about a patch or mod (whatever it gets called in the end) we might want to carefully consider the reliability and maintenance cost stats we assign to locomotives. I'm convinced that if people want some locomotives to be reliable, and want that reliability to be usable in terms of keeping the thing running for a longer period, and aren't just blindly going to ignore the cost of it all, the only way to do it within the limits of the game engine is to assign maintenance cost by using a combination of purchase cost and reliability rating. The game makers seem to have done this to some extent, but they don't seem to have got the balance right.
IOW, a loco with "Poor" reliability might have an initial yearly maintenance cost of 15% or 20% of purchase price, while a loco with a "Very Good" rating might only have an initial maintenance cost of 5% of purchase price. That way, the more reliable one might still be economic to run after a longer period, since the maintenance cost is hard-coded to increase by around 10% per year for all locomotives regardless of their rating, and this automatically means older ones cost quite a bit to run.
Given that the game's ratings don't actually tell you much, I'm providing some helpful translations based on my experience with the game.
![Mr. Green :mrgreen:](./images/smilies/icon_mrgreen.gif)
These translations assume that you want two things from your locomotives: good profit (ie: no point running all over the place if will hardly haul any load) and good reliability (ie: no profit if it aint moving, or if it stops other trains moving). This means you'll probably be the sort of person that thinks about replacing locomotives as soon as they start showing signs of breaking down more than very occasionally.
![thumbs_up !*th_up*!](./images/smilies/ok.gif)
A Helpful Translation, Into English, Of RT3 Reliability Ratings
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Rating of "Very Poor" means, in English, "if very well maintained and used fairly hard, will only be good for canning dog food after 3 years".
Rating of "Poor" means, in English, "if very well maintained and used fairly hard, should be melted down and recast as manhole covers after 5 years".
Rating of "Below Average" means, in English, "if very well maintained and used fairly hard, might make a good static tourist attraction after 7 years".
Rating of "Average" means, in English, "if very well maintained and used fairly hard, would only be useful for artillery practice after 9 years".
Rating of "Above Average" means, in English, "if very well maintained and used fairly hard, will actually give decent service for up to 12 years".
Rating of "Good" means, in English, "if very well maintained and used fairly hard, can soldier on for 18 years before becoming uneconomic to maintain".
Anything above that will probably be fine for the length of the average RT3 scenario, as long as you don't mind the escalating maintenance costs.
The term "Very well maintained" means that oil level never drops below 60%. IOW, it is not achievable by relying on the locomotive automatically using inline maintenance sheds, and has to be done with scheduled maintenance stops at all times. If relying on automatic use of inline maintenance sheds, deterioration in reliability will be faster.
The term "used fairly hard" means up to 6 cars of any type, plus caboose, in flat terrain. If trying to haul more cars, or trying to haul 6 up harsh grades, deterioration in reliability will be faster.
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From this you can see that a Consolidation, for example, is really only good for 8 years or so of service, while an H10 2-8-2 can be kept for roughly twice as long if you don't mind the maintenance costs.
Maintenance costs are the killer with reliable locomotives in RT3, since maintenance costs increase by roughly 10% per year. Here's roughly how your ongoing maintenance costs for an H10 2-8-2 look:
Year 1: $16,000
Year 2: $17,600
Year 3: $19,360
Year 4: $21,296
Year 5: $23,426
Year 6: $25,768
Year 7: $28,345
Year 8: $31,179 (which is roughly double the initial yearly expense)
Year 9: $34,297
Year 10: $37,727
Year 11: $41,500
Year 12: $45,650
Year 13: $50,215
Year 14: $55,236
Year 15: $60,760
Year 16: $66,836
Year 17: $73,520
Year 18: $80,872
Year 19: $88,959
Purchase price for a brand new H10 2-8-2 is $170,000. The maintenance costs for Year 18 and 19 are sufficient to buy a new locomotive. This means (IMO) there is no point keeping the old one for any longer than this. It makes more sense to dump the old one somewhere around 16 or 17 and get a new one, even if the old one is still fairly reliable.
Or, take that cute little American 4-4-0 as an example. Purchase price is $40,000. Initial maintenance cost is $7,000. Costs escalate like this:
Year 1: $7,000
Year 2: $7,700
Year 3: $8,470
Year 4: $9,317
Year 5: $10,249
Year 6: $11,274
Year 7: $12,401
Year 8: $13,641 (which is roughly double the initial yearly expense)
Year 9: $15,005
Year 10: $16,506
Year 11: $18,156
Year 12: $19,972
Year 11 and 12 maintenance costs are roughly equal to the cost of a new engine, and by 11 or 12 years of age an engine that started out with "Below Average" reliability will not be delivering very reliable service anyway. The smart option is to throw the thing away before it's 10 years old and get a new one.
![thumbs_up !*th_up*!](./images/smilies/ok.gif)
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Ok, so what does this all mean for locomotive replacement intervals? I've crunched some numbers for that too. Let's assume you have a reliable locomotive. It will keep running as long as you like, so the only consideration for replacing it is running costs. Let's also assume it has a fairly normal IAMC of 10% of purchase price, increasing at the hard-coded rate of 10% per year. From this you can work out the total cost incurred when replacing at different intervals.
For a first example, assume you keep the thing 10 years, then buy a new one. That means you buy two over a period of 20 years, meaning that adds up to 200% of the purchase cost for one loco. The escalating maintenance costs for one loco over a 10 year period add up to 159.4% of the purchase cost. That means for replacement every 10 years your total cost will be 100% + 159.4% + 100% + 159.4% for a total of 518.8%.
Ok, let's say you want to economise and decide to replace every 15 years. This is clever because it will save you money, right?
![Mr. Green :mrgreen:](./images/smilies/icon_mrgreen.gif)
Ok, so over 15 years your escalating maintenance costs for the first loco will add up to 317.7% of the initial purchase price. You still have to buy two locos, so that's another 200%, and you still have to pay 5 years escalating maintenance costs for the last 5 years, so that's another 61.1%. This gives a total of 578.8%.
The net result is that by "economising" and keeping that first loco for 15 years instead of 10, you have incurred an extra cost equal to 60% of the purchase price of the locomotive.
![cheers (0!!0)](./images/smilies/cheers.gif)
ETA: Corrected text added from here on. I shouldn't do complex maths late at night.
![Wink ;-)](./images/smilies/icon_wink.gif)
To make it economical to keep the locomotive for 20 years instead of 10, the initial annual maintenance cost would have to be reduced from 10% of purchase price to 3% or 4%. A loco that has an IAMC of 4%, replaced every 20 years, will cost about the same as a loco that has an IAMC of 10% replaced every 10 years. IOW, neither of those two options will save you money compared to the other option if the purchase costs are the same for both locos. They're about break even.
If the more reliable loco had an IAMC of 3%, then it would start to be cheaper to buy one of those and keep it for 20 years, instead of buying another 2 locos for the same price each, that had an IMAC of 10%, and keeping them for 10 years each.
If you want a locomotive to be economic to keep in service for 20 years, the initial annual maintenance cost has to be much lower than you might think. If this causes problems with scenario balance (which is possible) it might be possble to compensate by adjusting cargo prices, or giving the more reliable ones less spectacular performance, or something else.