## Reverse-facing locomotives contribute to total train power

Ideas, that are too old (too much things changed) or won't be implemented cause of some reasons or if there are obvious better suggestions.

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KoblerMan
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### Reverse-facing locomotives contribute to total train power

##### What is this "problem"?
Hello fellow Nauvians,

My request is a very simple one. It's a feature this game has been missing for far too long, and it has some pretty big implications for people who use double-headed trains, and even general QoL.

In the game's current state, trains that are on a multiple locomotive configuration will behave differently depending on which direction(s) the locomotives are facing. I will diagrammatically illustrate my point by showing a few examples of this.

Legend:
> - Forward-facing locomotive
< - Rear-facing locomotive
= - Cargo/fluid wagon

Trains in a configuration where all locomotives contribute power:
==>, ====>>, >====>, ==>==>, etc.

Trains in a configuration where only forward-facing locomotives contribute power:
<====>, ====<>, etc.

The main takeaway from this is that if a train is moving from left to right in these examples, the locomotives facing to the left are just dead weight.
##### How can we fix this?
Simple: make the locomotive facing the opposite direction of how the train is moving also burn fuel and contribute power to the train.
##### Why should we even do this?
Locomotives actually weigh a lot and cost fuel efficiency and speed because the locomotive facing in the direction the train is moving has to do all the work. In a system that's primarily 1-4-1, the locomotive in the rear will not do anything until the train stops somewhere and then switches directions. This behavior means that there is a tradeoff between sacrificing compact track layouts (i.e. no loops, two-way tracks in stations) for acceleration and fuel efficiency.

In real life (at least in the US, I can't speak for other countries), it is very common to see freight trains that are dozens of wagons long that have multiple locomotives in the front and sometimes one or two in the rear. Unlike in Factorio, the direction the locomotives face are irrelevant to the power contributed. All of the locomotives are synchronized and controlled simultaneously by the driver. This means for instance you can have a train which is 100 cars long with a configuration like this, where all of the locomotives contribute:
<=[...]========<><>

Where I'm from, this config is pretty common on big freight trains IRL. Factorio really needs this in my humble opinion, because it will allow the player to have twice as many options when designing their train conventions, and incentivize the space efficiency gained with double-headed trains.
##### Potential design challenges
This is more on part of the player's design rather than any challenge with implementation. Since I'm not a developer I can't speak to how difficult this would be to implement, but because it's not some abstract or ambitious idea I would imagine it's pretty simple (unless it breaks something.)

In single-headed trains, how does the player prevent them from moving in the wrong direction, or arriving at the station facing the wrong way? Well, you could design around this by making your train configurations symmetrical or getting clever with signal placement or loops to prevent trains from turning around.

What about the aerodynamics coefficient? Yeah, if you didn't know about this, locomotives have a bonus to aerodynamics which reduces acceleration time if they're facing the same direction they're moving in and are towards the front of the train. This is pretty easy to pull off if you have single-headed trains, just have all of your engines in the front.
##### Conclusion
I really think that this simple change to train behavior is a no-nonsense solution to an otherwise significant problem with running double-headed train conventions. As someone who always prefers double-headed trains, but always thought their behavior seemed a bit incompetent, I've really been wanting to see this and I've simply put off writing up a suggestion for it until now. With the new train stop feature implemented post-release in 1.1, it makes sense to me that our great Wube overlords might not ignore this post.

Anyway if you got this far, thanks for coming to my TED talk. Let me know what you guys think of this idea!

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### Re: Reverse-facing locomotives contribute to total train power

If you're not averse to using mods, you should try out Multiple Unit Train Control.
A good mod deserves a good changelog. Here's a tutorial (WIP) about Factorio's way too strict changelog syntax!

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### Re: Reverse-facing locomotives contribute to total train power

Pi-C wrote:
Wed Oct 21, 2020 1:12 pm
If you're not averse to using mods, you should try out Multiple Unit Train Control.
I will definitely check this out. Thanks!

EDIT: I did look at this mod and my one gripe with it is that based on the description, only one of the engines consumes fuel? That doesn't make a lot of sense to me, but I get that modders have limitations.

Also, I tend to play on vanilla only but I'm not super opposed to mods. Either way it would be great to have this feature make it into the base game.

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### Re: Reverse-facing locomotives contribute to total train power

KoblerMan wrote:
Wed Oct 21, 2020 1:14 pm
I did look at this mod and my one gripe with it is that based on the description, only one of the engines consumes fuel? That doesn't make a lot of sense to me, but I get that modders have limitations.
There is a setting where the fuel automatically balances itself now and then. But it doesn't really matter. One locomotive will consume first and the second on the return trip. So it evens itself out. It's not like you are constantly monitoring fuel consumption in real time.

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### Re: Reverse-facing locomotives contribute to total train power

If this were added, why use single headed trains at all? You are getting rid of a choice (acceleration or space) and replacing it with a “right way”
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### Re: Reverse-facing locomotives contribute to total train power

AmericanPatriot wrote:
Wed Oct 21, 2020 7:52 pm
If this were added, why use single headed trains at all? You are getting rid of a choice (acceleration or space) and replacing it with a “right way”
It's not getting rid of a choice, it's essentially just a buff for double-headed trains. Single-headed trains still have some advantages, the main one being that you save on materials by only having one locomotive.

I daresay in Factorio, there is no "right way" to do things. You can increase efficiency in a setup and call that the right way, but ultimately it's different strokes for different folks - someone might know the advantages of double-headed trains if this feature gets implemented, and simply go with a single-headed convention instead. It all comes down to that player's design choice.

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### Re: Reverse-facing locomotives contribute to total train power

Serenity wrote:
Wed Oct 21, 2020 2:39 pm
KoblerMan wrote:
Wed Oct 21, 2020 1:14 pm
I did look at this mod and my one gripe with it is that based on the description, only one of the engines consumes fuel? That doesn't make a lot of sense to me, but I get that modders have limitations.
There is a setting where the fuel automatically balances itself now and then. But it doesn't really matter. One locomotive will consume first and the second on the return trip. So it evens itself out. It's not like you are constantly monitoring fuel consumption in real time.
I can see a potential edge case with this where the train makes stops at more than just 2 stations, or stops at a signal for another train at random intervals, to the point where a round trip does not cost an even amount of fuel for each locomotive. If one of them runs out when it's that locomotive's turn to "drive", you might have another locomotive with fuel left that can't do anything. Although... I suppose this is also the default behavior of current double-headed trains?

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### Re: Reverse-facing locomotives contribute to total train power

I believe it is like this to force the player into making a choice as @AmericanPatriot points out. We have to choose, and problem solve each particular set up.
• Forward only locomotives need some kind of turn-around and/or dual track between stations. Also, the player needs to provision routing of the tracks to allow entry and exit. The benefit is all power is used for acceleration, braking, and top speed.
• Forward and back facing locomotives can take advantage of simpler, single track layouts. They come with the cost of having to drag a dead load (opposite facing loco)
Everything in factorio has a cost benefit equation, so by adding this buff, it would remove any kind of dilemma, or problem solving from the gameplay. I cannot support this proposal on this basis.

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### Re: Reverse-facing locomotives contribute to total train power

I agree very much with some of the other comments. The current game rules require the player to make choices and solve problems. IMO that is a good thing. I personally am here to solve problems and face challenges. Factorio is a complex game and IMO that makes it interesting and furthermore is actually one of it's biggest assets if not the single biggest asset. If anything, complexity should be increased, not reduced.

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### Re: Reverse-facing locomotives contribute to total train power

AmericanPatriot wrote:
Wed Oct 21, 2020 7:52 pm
If this were added, why use single headed trains at all? You are getting rid of a choice (acceleration or space) and replacing it with a “right way”
idk, still consuming more fuel and longer trains due to more locomotives to move in both directions. it's not free from a UPS perspective either. i don't buy your argument.
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### Re: Reverse-facing locomotives contribute to total train power

KoblerMan wrote:
Wed Oct 21, 2020 8:12 pm
the main one being that you save on materials by only having one locomotive.
That is really no advantage at all: everyone would use two headed trains regardless.
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### Re: Reverse-facing locomotives contribute to total train power

ptx0 wrote:
Thu Oct 22, 2020 4:27 am
consuming more fuel
No one really cares about fuel use.
ptx0 wrote:
Thu Oct 22, 2020 4:27 am
longer trains due to more locomotives to move in both directions
The request is that the trains wouldn't be longer but the same size as single headed trains.
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### Re: Reverse-facing locomotives contribute to total train power

I’m against this change.
Reason is: it’s a quite old suggestion and discussion has always been going around, that there are good reasons for this top and trail system. (See also this article that explains the jargon: viewtopic.php?p=102302#p102302 )

It’s bidirectional trains, terminus layout .vs. roll on/roll off but loop based layout.

There was never a clear winner in the discussions. And to my personal feeling: both layouts are feeling pretty balanced against. There would be no more good reason to build loop based layouts if the train length would be equal (because you need not double the amount of locomotives).

What keeps - and which seems to be a good argument - is that in real live reverse locos contribute to the propulsion of the train. But that is not a good argument for a game. Game-play value doesn’t increase much with this change.

What I would (meanwhile, I changed my opinion) really like instead is
viewtopic.php?f=6&t=32177 Turntables + Automated Detaching

Former discussions:
viewtopic.php?f=6&t=14743 Push-pull trains? [recommended, and I’m sorry, I didn’t find other posts in suggestions before that, even if I said “already discussed before”, maybe in another board... but I think I pointed the arguments quite well out]
viewtopic.php?f=71&t=26719 Locomotives should be able to run backwards [only a similar suggestion]
viewtopic.php?f=5&t=35806 RoRo vs Terminus (was Loop vs 2-headed train network)
viewtopic.php?f=6&t=40644 propulsion power of bidirectional trains
viewtopic.php?f=6&t=59429 Locomotives capble to drive in reverse.
viewtopic.php?f=6&t=55723 Trains should be willing to auto-reverse course
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### Re: Reverse-facing locomotives contribute to total train power

I think reducing the weight of Locomotives would be a better way to balance the two systems.

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### Re: Reverse-facing locomotives contribute to total train power

AmericanPatriot wrote:
Thu Oct 22, 2020 5:47 am
KoblerMan wrote:
Wed Oct 21, 2020 8:12 pm
the main one being that you save on materials by only having one locomotive.
That is really no advantage at all: everyone would use two headed trains regardless.
I don't think "everyone" will suddenly switch to double headed trains. But, people will consider double headed trains a bit more.
Double headed trains have the downside, that they might arrive reversed at the station and this can be a problem with unsymmetrical trains. Also, signalling is quite different. UPS friendly folks probably use double headed anyway to avoid loops.

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### Re: Reverse-facing locomotives contribute to total train power

I'll be honest, I wasn't exactly expecting 66% of people to try and shoot this down over balance concerns. If you don't like double-headed trains, nobody is forcing you to use them, guys.
AmericanPatriot wrote:
Thu Oct 22, 2020 5:49 am
ptx0 wrote:
Thu Oct 22, 2020 4:27 am
consuming more fuel
No one really cares about fuel use.
Except for the people who have a centralized megabase late game, and actually have to account for fuel range. What happens when you send a train out tens of thousands of tiles to a mining outpost, and it runs out of fuel? This is more of a problem than you might think late game, especially if you're not running rocket or nuclear fuel.
ssilk wrote:
Thu Oct 22, 2020 7:05 am
There was never a clear winner in the discussions. And to my personal feeling: both layouts are feeling pretty balanced against. There would be no more good reason to build loop based layouts if the train length would be equal (because you need not double the amount of locomotives).
I think I've explained this well enough already, you still get a tradeoff. Yes, depending on how you look at it, you could argue that double-headed trains become less balanced. But I really don't see this as a game breaker.
ssilk wrote:
Thu Oct 22, 2020 7:05 am
What keeps - and which seems to be a good argument - is that in real live reverse locos contribute to the propulsion of the train. But that is not a good argument for a game. Game-play value doesn’t increase much with this change.
I will have to vehemently disagree with this, especially since I don't see a problem with in-game stuff being modeled after real life as long as it's not necessary to have an acceptable break from reality. Why make a game where you arbitrarily remove functionality from something like this, unless there is a legitimate balance concern? If anything this is more of a QoL addition than some massive balance change. That's why I think this adds to gameplay value, if I thought it didn't I wouldn't have suggested it.
jodokus31 wrote:
Thu Oct 22, 2020 10:38 am
AmericanPatriot wrote:
Thu Oct 22, 2020 5:47 am
KoblerMan wrote:
Wed Oct 21, 2020 8:12 pm
the main one being that you save on materials by only having one locomotive.
That is really no advantage at all: everyone would use two headed trains regardless.
I don't think "everyone" will suddenly switch to double headed trains. But, people will consider double headed trains a bit more.
Double headed trains have the downside, that they might arrive reversed at the station and this can be a problem with unsymmetrical trains. Also, signalling is quite different. UPS friendly folks probably use double headed anyway to avoid loops.
See, this is what I'm talking about. I think we stand to benefit from this change a lot more than we stand to lose. And I really don't see it as unfair from a balance standpoint.

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### Re: Reverse-facing locomotives contribute to total train power

KoblerMan wrote:
Thu Oct 22, 2020 12:31 pm
I'll be honest, I wasn't exactly expecting 66% of people to try and shoot this down over balance concerns. If you don't like double-headed trains, nobody is forcing you to use them, guys.
You are correct. nobody is forced, but with the buff, there becomes a single, obvious choice.

I'm not against this per se, and as a mod it would satisfy those that don't want to have to make any kind of decision regarding train wrangling, and that is entirely their prerogative. I simply feel it should not be a vanilla buff. It's not just a balance dilemma - "easy option" is not the premise of the game, and in some ways its inclusion could devalue Factorio (a little). This is of course my humble opinion.

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### Re: Reverse-facing locomotives contribute to total train power

Squelch wrote:
Thu Oct 22, 2020 1:06 pm
KoblerMan wrote:
Thu Oct 22, 2020 12:31 pm
I'll be honest, I wasn't exactly expecting 66% of people to try and shoot this down over balance concerns. If you don't like double-headed trains, nobody is forcing you to use them, guys.
You are correct. nobody is forced, but with the buff, there becomes a single, obvious choice.

I'm not against this per se, and as a mod it would satisfy those that don't want to have to make any kind of decision regarding train wrangling, and that is entirely their prerogative. I simply feel it should not be a vanilla buff. It's not just a balance dilemma - "easy option" is not the premise of the game, and in some ways its inclusion could devalue Factorio (a little). This is of course my humble opinion.
Sure, but having a single obvious choice just means you've discovered a more efficient way of doing things. You could compare this to figuring out what the ratio is for your smelting column - at that point, once you see the superior method, that becomes the single obvious choice, at least to that player. I would argue that this IS what Factorio is all about.

And yeah this is all just my opinion too.

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### Re: Reverse-facing locomotives contribute to total train power

I'm also in the camp of "if a locomotive is facing the wrong way, it shouldn't contribute to motricity". I like the current tradeoff space needed/throughput/speed of the train/convenience better than the one your suggestion would achieve.
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### Re: Reverse-facing locomotives contribute to total train power

I'm also in the camp of "if a locomotive is facing the wrong way, it shouldn't contribute".

Bidirectional trains have easier train stops but are a little slower, while unidirectional trains are a little faster but train stops need more space. I like when a player is forced to decide.

There are also other problems when locomotive in wrong direction would contribute: would that mean a train with all locomotives heading into one direction should be able to find a path in opposide direction and travel entirely in reverse? What if there would be 100 locomotives in one direction and a single one in opposite?