Designing the QA system in Production Line


(re-post from blog at … tion-line/)

This is a big feature in my car factory game Production Line that I have been putting off until I could really set aside some time to think about the design seriously. I think I’ve finally reached that point in Early Access where I need to flesh out the design for this part of the game, and also importantly, to listen to feedback from current PL players about how they think this should work.

The current system is pretty simple. cars have work done to them on the production line, and then at the very end of the line, just before export, they go through a pre-export QA process that is broken down into emissions test, visual inspection and performance tests. All cars are assumed to be thoroughly free of defects, and are sold on the basis of their features and their price relative to the perceived value of those features.

Obviously in the real world, defects and car quality is a thing. You wouldn’t expect any defects on a $150,000 car, you would expect very few on a $70,000 car (unless its panel gaps on a tesla…dig dig…), and probably be more tolerant of minor things on a cheaper car. High end car companies (Rolls Royce etc) probably go overboard on quality assurance to ensure a reputation for zero problems (Lexus are also good at this), whereas at the lower end, its probably less of a concern. How to best represent this in the game in a way that both feels reasonable, and makes intuitive sense, and also works within the existing game design, and above all feels interesting and fun?

For a while, I have wanted to combine the idea of defects with the introduction of an area-of effect mechanic. One of the most interesting aspects of the game is the designing the layout of your factory, and at the moment, apart from making sure importers and exporters are in the right place, and ensuring that you only place office slots (like research) in office zones, there is not that much positional decision making involved in the game. I thought I could introduce this with the advent of new QA slots, that had a radius effect.

The system would work by generating defects at every point along the line. there would be a base level of defects that would be generated each time a task was carried out on a vehicle, including tasks generated through upgraded slots. For example, adding the rear axle = 1% chance of a defect. Adding a tire pressure sensor… 1% chance of a defect… and so on. Some cars would go through the line entirely free of defects, but many would not. Eventually, if ‘untreated’, those defects would make their way into the final cars which would be sold.

For every car sold with defects (depending how many), there would be a negative impact on the reputation of your brand, a new, lagging indicator which would affect the purchase enthusiasm of your customers. Obviously this would be something you would want to keep an eye on, so as to ensure customers were not turned away, so how do you prevent defects? and how do you treat them?

To prevent defects, you can place down QA stations, which would be area-of-effect based, and would essentially reduce the percentage chance of a defect occurring at any specific point on the line. Covering the entire production line with regular QA slots would be a way to keep production quality high and defects low, but obviously would have a cost in terms of employee pay and the floor-space required to add those QA stations. This would be a ‘prevent defects from ever happening’ approach to QA. The second approach would be to introduce a new ‘re-work’ slot right at the very end of the line (maybe just before the current QA section) which would examine each car, and take whatever time is needed (maybe 2 minutes per defect?) to fix the problem and allow a perfect car to travel beyond that point. Clever players would eventually use smart junctions (which would need defect-based rules added to them) to ensure that cars that randomly seemed to be defect-heavy did not cause a major slowdown. As I understand it, in real factories, cars that need re-work are immediately taken off the line and dealt with separately so as not to cause any real bottleneck.

This is my first attempt at designing a QA/Quality system for the game. I’m very interested to know what existing (or potential) players of the game think. Essentially it boils down to this:

Defects are randomly generated on cars as they are constructed
Area-of-effect QA stations reduce the likelihood of those defects when placed on the line
A re-work area can optionally be placed to fix defects at the end of the line
Defects will affect the brand image of the company, and thus customer eagerness to buy.



I am very excited about the inclusion of Quality Assurance in the game.

Here is my take on it.

There are Four key areas that need to be covered for a comprehensive QA / QC system.

  1. Vehicle Production

  2. Parts Manufacture

  3. Testing

  4. After Sales Service

  5. Vehicle Production.
    I would like to be able to upgrade a slot to have Quality Control. This expensive upgrade can be a small visual sprite such as a QA Station, Yellow strobe light or even a Robot/traffic intersection light (Red, Yellow, Green) . Easy and cheap (i assume) to build. The upgrade can also be implemented multiple times such as with the robots, and add a delay of say 5 seconds on first upgrade, 10 seconds on second and 15 seconds on third upgrade.

Each slot should have am inherent 1% chance of a fault and equally each component at that slot should have a 1% chance of generating a fault.
Every production slot should have this upgrade option.

  1. Parts Manufacture
    All manufacturing slots should also have an expensive Quality Control upgrade slot, with a sprite (as above) to indicate that the upgrade has been effected. Again each slot will have a 1% chance of developing a fault.

  2. Testing
    The Re-work station has enormous potential. For it to function correctly there should be a larger amount of time at the current (3) QA Stations.
    These do after all have a look at vehicle specifications being met, gaps and profile checks on the bodywork, exterior checks on body, touch and feel checks on the paintwork, Mechanical and electrical checks, Rattle checks, etc. The best option would be to include these additional checks into the three existing QA Stations. If a vehicle is flagged with any defect then it needs to run off to the Re-work station.
    The smart junction idea really excites me as this is possibly the most underutilised feature in the game.

The Re-work station should in essence be made up of more than one slot. There should be a slot for Chassis, Body, Paint, Engine, Accessories and Electronic Fault Repairs.
Once cleared of all the flags (defects) the vehicle should then return to the 3 existing QA Stations before passing on to the Export slot.

Something currently missing from the game (other than Quality Assurance and Quality Control) is the Valet option. The vehicles need to go through a cleaning station where they are cleaned and shipping protection is added (plastic seat covers, etc).

So in essence you would have the three QA Stations, then the six fault repair stations, a return to the QA stations before entering the Valet station and then finally export.

  1. After Sales Service
    To reduce the impact and potential of product recalls and consumers negative reactions to any product faults , there should be a Quality Assurance Office which generates points. These points are consumed by each vehicle sold, so that there is a need for these offices. Another game mechanic could also be that higher your accumulated points are, the lower a chance of a production or manufacturing slot developing a fault.

This is how I see it in a nutshell.

A great game Cliffski, and really looking forward to updates 1.49 and beyond.


I definitely think that 2 elements are needed regarding vehicle quality (component quality is interesting, but something I think can be handled after vehicle quality is done).
Firstly I think we definitely need a way to reduce the amount of defects along a line as the car is assembled.
Secondly we need a final rework option that fixes all the final defects before they are sent out for export.

We could re-engineer the smart junction so it can also select cars not just by design but by defects, sending defective cars one way and perfect cars another way.
A new feature can be added to the ‘visual inspection’ slot which ‘spots’ features. This would mean that you cannot use a smart junction on a cars defect status UNTIL those defects have been spotted.

That then allows the player to put down a visual inspection & smart junction/rework station wherever they like along the line, not just right at the end.

Add to this a system where each additional component added to a car increases the ‘fix time’ of each defect by a certain amount, and the player now has a financial(time) incentive to have multiple visual inspection slots and rework slot /smart junction setups along their line.

Actually thinking about it… it might be worth keeping the visual inspection as it is, and just calling the new one a ‘quality assurance’ slot, and maybe build the smart junction into the slot, thus making it m,ore obvious to the player (and less confusing) how its used? I could even have the rework facility included so the whole thing has to be placed as a sort of blueprint? or maybe thats too restrictive…


Hi, here’s my suggestion.
The rework station is a must and I like the junction that splits defective from non defective cars.
I would use a QA office (that would go in the office area) and basically have random defects pop up on a random ocurrence. Say for instance theres a problem with the lights station. Your QA inspection station can point that out inmediatly, however the root cause of the defect wouldnt be apparent until further analisis and the cars affected by this deffect would go up over time. Your QA office starts doing the analysis inmediatly afcter the defect is picked up (and it would work same as research, points over time) and once they figure out whats wrong (say for example: malfunction on the robot algorythm, or low quality bulb from supplier, etc) you get a pop up that a allows you to fix it so you wont have any more defective cars from that station (at least for a while). If you dont have a QA office basically there would be a point where all your cars would be having a deffective head light and all of them would go trough the rework station. If you dont want a QA office you can replace the entire headlight station (wich should be more expensive) that way you can also “play with the balance”. Say i have a big factory and 4 different stations are trowing defects. I only have 2 QA offices so instead of putting down more QA Offices to speed up points i can choose to replace 2 of those defect generating stations and have the QA solve 2 problems instead of 4.
The idea driving my line of tought is QA is not cheap but it definetly is cheaper in the long run.
Also probability of defects should increase with how old is an station. That just gave me another idea for later: Maintenence department.
Thanks, and again: awesome game.


So after watching the development blog earlier this afternoon I’ve had a sit and think about how I would expect/like QA to work in the game. I’ve then gone online and read the posts before mine in this thread and realised that what I came up with Cliffski has already kinda described anyway. So without wanting to repeat what’s already been said I’ll go through what I was thinking.

So my initial thoughts were well why not just do some sort of check at a slot at the end, but like Cliff says in his vblog, trying to fix part of a car that’s buried under a load of plastic or carpet or even just other equipment after the install would be a long and laborious process. So this leads me to the main concept that I’d that then rules the entire system in a way.

At the point of finding the fault, the longer it has been since the part was fitted, the longer it takes to repair the part.

For example, if you place the Quality Control Slot (just what I’m going to call it for the purposes of describing the system) right at the very end of the production line and it turns out that the part that’s broken if the front axle then it takes an appropriately ridiculous amount of time to fix the vehicle, say 30 minutes.
If however you place a Quality Control Slot after the Chassis Assembly part of the line has been finished, so you’re only 4/5 slots from the point of the faulty axle being fitted, then it takes significantly less time to repair the part, say 5 minutes.

This can then obviously be repeated on it’s way down the line with Quality Control slots being put after each section, or even each slot if someone wanted to get real picky with it, to try and pick up faults before it’s too late.

As Quality Control process has been running throughout the factory I then got on to thinking, do we need the visual inspection slot at the end of the line? I’d then argue no because the vehicle has already been checked along the line numerous times. Instead I’d suggest that the Quality Control slot actually replaces it. This means that there is now a requirement for the vehicle to be checked before sale and there has to be an element of quality control. The order would then be Quality Control, Performance Check, Emissions Check. The QC slot however can be placed, in addition to the one at the end, wherever the player likes on the production line so it’s up to the player if they want to try and fix the issues as they go along or just in one big cohort at the end of the line.

I’d suggest that the Quality Control slot runs for a fixed period of time, say 4 minutes to check the vehicle before sending it for repair. This means that it doesn’t matter if the played put’s it earlier or later in the factory it always takes the same amount of time. To add a research element to the slot to develop the late game play with it, the ability to research specific Quality Control slots for sections of the factory could be something interesting. These slots would run significantly quicker that their generic counter part, giving the player something to research later in the game. So like the Chassis assembly slot breaking down into numerous sections, the QC slot breaks down into multiple sections too.

Now in terms of the actual slot itself I had a think about this too. My thoughts we’re not too dissimilar to Cliffskis initially thinking of utilising the smart junctions so that the Quality Control slot logs some sort of flag on the vehicle that when it hits a smart junction can be sent the relevant direction to go and get repaired. I then thought can a slot have two exits, so that the slot was placed onto the map as a slot with one entrance and two exits, one for a passed vehicle, the other for a failed one. This I thought seemed the better option. Cliffski suggested in his post earlier about including a smart junction as part of the slot which seemed to make sense to me. On further consideration though trying to route the conveyor from two exits of a slot when there is multiple of the same slot together would become a nightmare if you wanted to keep them separate to send them all to a “repair slot”. So I’ve actually gone back to my original thinking now of a slot that generates a flag so that the cars due for repair can easily be separated out from multiple slots together.

I think this would be better as the system that I thought to use would not have the Quality Control slot actually repairing the vehicle but a secondary repair slot. This slot would then run for the appropriate amount of time to repair the vehicle from very long, to much shorter time periods. If we go back to the idea of having a split exit from the Quality control slot it would be quite easy to place on of these straight after. The issue would come about though if you have 4 Quality Control slots and 4 repair slots, as luck would have it the same Quality control slot finds two vehicles in a row that need something swapping. This now leaves you with two vehicles Queueing to use the same repair slot when others are sat idle. This isn’t effecient. By having 1 exit from the control slot so all the exits from the Quality Control slots lead to the same conveyor you can break the repair vehicles off down the line with a smart junction and send them to a bank of repair slots so that the process can run in parallel instead of serialy.

So… That was an awful lot of typing which potentially doesn’t make a great deal of sense and is probably grammatically poor. I hope that makes sense to you Cliffski and others and I’d love to hear what your thoughts are.


Fairly new player, but I’ll provide some feedback on the current implementation of the QA system as of version 1.53.

In general, I think this is more confusing than it needs to be. Up first is the fact that the showroom shows defects, but I never found a single defect on the factory floor. The “visual inspection” phase of the multi-function slot “quality check” apparently doesn’t flag defects, but the single-function slot “visual inspection” does. Only when I finally got around to researching “quality specialization” and subsequently placing a single-function “visual inspection” slot did I see cars finally flagged as having defects. This is very confusing and seems to go against the other single- vs. multi-function slot behavior. Aside from upgrade potential, they all do the same thing at the expense of time efficiency.

You wouldn’t know it starting a new game but the visual inspection, as part of a single- or multi-function slot, isn’t actually needed to get a car to the showroom. Only the emissions and performance checks are required. This essentially means that the visual inspection function of the multi-function “quality check” slot accomplishes nothing other than adding a bit of a value (as a “feature”) to the finished cars. You’re also forced to place it down in order to access the other two checks before specialization can be researched.

Two choices here:

  1. The “visual inspection” phase of the multi-function slot “quality check” should accomplish the same thing as it’s single-slot counterpart to be consistent.

  2. “Visual inspection” should be removed from the multi-function slot “quality check” and just be a researchable single-function slot.

I’d recommend option 1 since it would at least allow the player to see the defects (the ones found anyway) in the interface before heading into the showroom. In the early game, a player may not be able to do anything about it, but looking at the defects in the showroom shouldn’t be a huge shock. The showroom should also make it clearer that you have a God-like visibility of defects at this point since some will show here that aren’t flagged by your QA (at least 20% if I understand this correctly).

You mentioned in your initial write-up above that perhaps there should be a new and separate QA slot that reduces defects. I’m going to assume for the remainder of the post that the single-function “visual inspection” slot has this function, even though it has the same name as described above. From reading and playing with this, it’s not at all clear how the “area of effect” applies to the factory. Is it proximity of the visual inspection slot to the other production slots or does it just affect a number of slots before regardless of how much conveyor is between them? If I ran a huge conveyor to a visual inspection slot in the corner of the factory with nothing else around, does this accomplish anything? I’d recommend slot / conveyor distance be irrelevant here since it makes more sense for inspectors to influence the slots before it (regardless of distance) by looking at the product coming down the line and not necessarily peaking into a neighboring slot. In the (not recommended) case of the latter, a visual cue should accompany placing the visual inspection slot to see what other slots it would influence. Finally, the visual inspection slot should have a statistic for prevention of defects to remind players that it has this function. Perhaps the “visual inspection” as part of the multi-function “quality check” slot should specifically omit this? May be a reason to have a third option of a newly named slot altogether that does this.

Last piece of feedback concerns the “perceived quality” statistic. While one can loosely conclude it influences buyer enthusiasm, how much of an effect are we talking? A player should have this information spelled out a bit to make an informed decision about when they should start heavily investing in QA, just like a real company. Right now it’s just a percentage that doesn’t seem connected to anything. I’ve been getting roller coaster type buyer activity which is making my funding levels unpredictable. Is this the cause? Not possible to know from the interface that I see, but perhaps I’m missing it.

After all of this, perhaps it’s best to create a new quality slot that provides the area of effect separate from all the other existing slots. That can certainly work too, but I think there needs to be some work down to figure where the visual inspection fits in to everything in that case.


Thanks for the feedback, this is very interesting. We gave up on the idea of any area-of-effect mechanic in the game after multiple players expressed a view that this would be more annoying than fun. The visual inspection only works specifically on the cars that go through it.
Regarding the component of the multi-task slot not doing the proper inspection job you are right, I will fix that so that this also happens, as its very confusing.

You also make a good point regarding not knowing the true impact of the perceived quality on actual sales. This is coded somewhere in the game but currently not made available to the player, and I do need to find out some helpful, and interesting way to do this.


So the only issue I think you’ll be left with is there’s nothing that can be done about all these detected defects until at least the middle game when QA specialization and rework are researched. Of course a player could prioritize these earlier, but they’re both relatively expensive techs. From a gameplay perspective, this just seems a little off with all these defect tags on the production line and no recourse to stop them. From a real-world perspective, I imagine six sigma (and other) practices are employed often to identify and reduce manufacturing defects early on. I think you’ll probably want to consider adding a passive ability to decrease defects to either a new slot or adding to the visual inspection slot as you originally proposed.

I agree that an area of effect with a certain diameter is probably not ideal based on your current design. As I casually mentioned in a prior post, why not have this passive defect reduction affect a number of slots before the inspection slot? It would provide an earlier game mechanic to start addressing the defect problem before the player has access to rework, and be a reason to use the visual inspection in other places other than the end of the line. It also makes real-world sense that this passive ability slot would detect the issue and trace it back to the offending slot (within range or reach of the inspection slot) and provide a reduction to the defect rate at that slot, simulating defect analysis and remediation. Perhaps the effect range is upgrade-able, adding more to the tech tree.

For now I think adding to the interface and removing the confusion is a great start. Ultimately, I think players will be wanting for defect reduction and prevention mechanics, not just rework, which I think play a large role on a real production line.

Just some suggestions!


I made the change today (and it turned out to be quite easy) to ensure that the visual inspection part of the initial QA task at least detects defects, which corrects an anomaly that meant the same task did different things depending on whether it had be broken out into a slot or not. This will be in the next patch.

Of course the player still needs to research (and implement) rework in order to actually fix those defects, but a player can decide to actively prioritize that part of the tech free relatively early I guess.