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Cities: Skylines >  Workshop > FretfulShrimp's Workshop > Traffic++ > Discussions
Traffic++
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leftbehind 29 Apr, 2015 @ 9:27am
Musings on traffic priority lanes feature...
I'll add brief request for this on the suggestion site, but wanted to put down some more verbose throughts here on why I think it's an important feature (perhaps moreso than the lane customisation)....

When I first started playing with intersection routing feature in latest release, I found it confusing. It took me a while to work out what was causing the confusion until I realised that I'd already tried to tackle lack of lane routing via a different method - one way streets.

I made surrounding roads 2-way, and suddenly the confusion I was having with intersection routing was gone (for the most part).

As traffic increases, there seems to be a natural sequence of how to deal with it, and if there are gaps in that sequence things start to get confusing. I think priority routes (like those Traffic Manager mod provides) are a missing feature from this plugin.

I've never really had the level of control over a road system that C:S and T++ gives me, so a lot of this stuff is new to me. But the sequence seems to be something like this:

1. Get basic road system up and running

2. Start using roundabouts to deal with some initial blunders in the road system

3. <missing> Define priority routes to ease congestion of arterial routes

4. <missing> Basic intersection route optimisation (TM style, eg. "no left turn")

5. Advanced intersection route optimisation (T++ style)

6. <missing, but Toggle Traffic Lights mod can be used with T++> Start using traffic lights

7. <missing> More elaborate control over traffic lights (timing, sequencing, etc)

8. Implement one-way systems to handle heavy traffic

9. Start using bigger roads (4-lane, 6-lane, highway overpasses, etc)

10. Segregate different types of traffic on existing roads with special lanes

11. Create dedicated roads for segregated traffic

The sequence above might not be correct, I'm still a n00b at traffic management and my city is still only around 40k people. I have much to learn. But at this point in time the above is what I perceive the evolution of traffic management to be as my city grows. I also base my approach somwhat on how I imagine it would happen in real life - where you can't just go around bulldozing entire city blocks to build new road systems overnight; so there is a desire to retain existing road system for as long as possible before having to take more drastic measures.

Features that are missing force me to over-compensate with other features, making subsequent features more confusing to use.
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Showing 1-15 of 51 comments
FretfulShrimp  [developer] 30 Apr, 2015 @ 3:20am 
First of all, let me say that I haven't used the Traffic Manager yet so what I'm saying next may not be entirely right.

From my perception of the game and from what I read on that feature, I believe that priority roads actually cause more traffic. Maybe not in all situations but in intersections with high traffic, where you'd want to use them.

Here's why: Imagine you have a T-intersection where every road gives priority to its right. If you have a constant flow of vehicles coming from the right, the other two roads will keep building up traffic as they're waiting for their opening to move. On the other hand, without any priorities, all vehicles will try to move and the game actually makes a nice job at finding gaps between cars. So, instead of having one road flowing well and two others waiting for their chance, you have three roads flowing at a slower pace which, IMO, is still better.

This is just an example but I can see this being the case in most intersections with a decent amount of traffic. And if the intersection doesn't have traffic, there's no reason to put priorities in the first place.

Regarding timed traffic lights, I think that's taking it too far. Sure, it's nice to have that kind of control but I think it would take too much time to get it right and its results wouldn't be worthwhile. And then, after your city grows up a bit more and traffic shifts from there to another intersection (or if traffic builds up even more in that intersection), you'd need to revise your timings again.

Now, this is my opinion without having actually tried so please let me know if I'm wrong. Let's discuss this further and see what everyone thinks about it.

Just to make it clear for everyone: We are just discussing it. There's no guarantees that this will ever be added to the mod, regardless of its conclusions.
#1
leftbehind 30 Apr, 2015 @ 4:00am 
I guess what I'm trying to describe as the flow or sequence of things to do as the city traffic grows could be related to this:

History of Medicine:

2001 BC Here, eat this root.
1000 AD That root is heathen. Here, say this prayer.
1850 AD That prayer is superstition. Here, drink this potion.
1920 AD That potion is snake oil. Here, swallow this pill.
1945 AD That pill is ineffective. Here, take this penicillin.
1955 AD Oops... bugs mutated. Here, take this tetracycline.
1960-1999 AD 39 more “oops”... Here, take this more powerful antibiotic.
2000 AD The bugs have won! Here, eat this root.

I'm sure you've seen C# / Java / Ruby / etc. equivalents of that on programming blogs.

Another analogy is Whack A Rat/Mole. http://urbananomie.com/wp-content/uploads/2013/09/2765541278_a18fe5606a_b.jpg - you keep bashing things that pop up, until you become overwhelmed with the results of your own actions and realise that the way to solve it is to stop fighting symptoms and tackle the root cause - unplug the machine and you win.

This is why people are flocking to Traffic Manager. It gives them tools that on the surface appear to solve a particular problem, but in fact just leads to more complex problems, and then there's tools that appear to solve that problem...

So, basically, the core game lacks a sufficient toolset for people to create increasingly complex symptoms for deeply rooted problems they're not even aware of. With the right set of symptom treating tools, people feel like they are in control of the situation when in fact they are just making it more complex. And that's fun because it's a learning process, just like the history of medicine above.

The result is a journey that people go on - tackling 'problems' with various tools as the city grows until they have enough wisdom to know that just a subtle road tweak will solve the root cause of the symptoms.
Last edited by leftbehind; 30 Apr, 2015 @ 4:07am
#2
FretfulShrimp  [developer] 30 Apr, 2015 @ 4:47am 
Ah, I see your point now and I agree that people like to feel they're in control, even if they really aren't.

But that is just another reason for me not to implement those features. I would be making tools that I don't feel are needed, to give people the feeling of control, just for them to later realize they don't actually need them and stop using them.

If people feel they need more control, they can put this in ghost mode and try the manager. Then, when "they have enough wisdom", they can opt to come back to T++. And maybe one day they'll be compatible and people that want control can use both.
#3
leftbehind 30 Apr, 2015 @ 5:00am 
The features wouldn't be totally useless though... For example, being able to define road/lane priorities at certain key intersections - like lanes leaving a roundabout - is still highly useful at small roundabouts that can clog up if too much traffic uses them. The various features come in very useful in smaller suburbs where major road works are not desirable - being able to fine tune the road system allows the existing roads to be retained for longer.

Regarding having T++ and TM working together, would that not require a merging of both the vehnicle AIs and the path finder? Having recently waded through the pathfinder code, I'm wondering how feasible that would be (especially taking performance in to consideration). I can see some scope in making pluggable AIs, but the pathfinder looks like it's going to be the main problem with integrating traffic mods.
#4
FretfulShrimp  [developer] 30 Apr, 2015 @ 8:28am 
In smaller suburbs there isn't enough traffic to cause problems (supposedly) but could you explain how priorities would help in lanes leaving a roundabout? I'm not sure I'm seeing a use case in there.

Merging would be the easier solution, surely. A common API that served all traffic-related mods could be done but it wouldn't be easy for the exact reasons you mentioned and I'm not seeing it happen anytime soon.

#5
leftbehind 30 Apr, 2015 @ 9:45pm 
If traffic is struggling to leave the roundabout, the roundabout can become jammed and that can cause a gridlock in the local vicinity, sometimes with huge tailbacks.

I've found the most common cause of such issues to be traffic from side roads clogging or slowing the main roundabout exit routes.

So the idea with the priority system is that it's a simplistic tool to stop traffic from side-roads clogging an arterial route. It allows the user to say "traffic along this stretch of road has priority at the specified junctions over traffic from side roads", thus giving a clearer stretch of road for traffic escaping the roundabout.

It will cause some traffic on the side roads which have to "give way", but that generally won't lead to gridlock.

In the UK we even have a special version of our "Give Way" sign just for roundabouts. http://en.wikipedia.org/wiki/Yield_sign

http://gtm.steamproxy.vip/sharedfiles/filedetails/?id=432487280
Last edited by leftbehind; 30 Apr, 2015 @ 10:11pm
#6
leftbehind 30 Apr, 2015 @ 9:53pm 
More technically... Currently, if it looks like a stretch of road to the next intersection will be full, traffic wanting to go there will wait at their current junction until the stretch of road has room for them before moving to that stretch of road.

The problem arises in that there's no way for users to tell the game which roads get to join the stretch of road first when it clears - the right of way / priority thing allows us to say "people coming form this road get to go first, people from side roads will have to wait". It's a subtle differnence in the traffic flow, but it can have huge improvement on overall traffic in the vicinity.

It will allow us to make sure that traffic in a certain direction flows as smooth as possible, even though it's at the expense of hindering other traffic.
Last edited by leftbehind; 30 Apr, 2015 @ 9:53pm
#7
leftbehind 30 Apr, 2015 @ 9:55pm 
BTW: The approach taken by TM mod seems to be more tailored to right-hand driving and US traffic regulations (based on the way he's visualised it in his mod): http://en.wikipedia.org/wiki/Priority_to_the_right

TM mod also enables the user to set a "Stop" for traffic from particular direction - not sure yet if this would actually be useful in C:S, I don't even think it's that useful in real life lol. http://en.wikipedia.org/wiki/Stop_sign
Last edited by leftbehind; 30 Apr, 2015 @ 10:04pm
#8
Stealthy 2 May, 2015 @ 2:01am 
The biggest thing on timed traffic lights option in TM is the ability to adjust green lights to each direction separately and control turning traffic independently. For example in T junction, core game sets green light to both left and right side at the same time and traffic turning from right to down will collide with left to right traffic. Now in timed traffic lights you can add a cycly which allows left to down, right to down and down to right movements at the same time without causing conflicting moves, providing all roads have enough lanes. This makes a massive benefit to lights and the throughput is way higher than on a normal behaviour. Which is why you should implement on/off switch to traffic lights and this same option. I wouldn't need the times itself, just the possibility to mod the sequenzes on the lights. And not even on all junctions, just the few in the busiest intersections would normally do.

Priority signs i found causing more issues than they actually resolved.
#9
FretfulShrimp  [developer] 2 May, 2015 @ 7:16am 
I understand now what you mean by traffic leaving the roundabout clogging up. But I get the feeling that using priority lanes to fix it it's just, as you put it, treating a symptom, not the root cause.


Originally posted by pasiltd:
The biggest thing on timed traffic lights option in TM is the ability to adjust green lights to each direction separately and control turning traffic independently.

I didn't know it allowed to do that. That's actually really nice and together with my customizer tool you could make vehicles turn into different lanes, increasing traffic flow eve more. Using your example, you could make cars turning down from both left and right at the same time and the ones from the left would use the outmost lane, while the ones from the right would use the innermost lane.
#10
Stealthy 2 May, 2015 @ 7:18am 
Make that happen, and ensure that this is compatible with the Improved Public Transport and i can already hear the paypal link being clicked :)

You are right, with the way your work allows the lane management combined with the traffic light management, it would be just awesomely powerful tool to manage the traffic and by far the best mod to do that. Go for it! :)
#11
FretfulShrimp  [developer] 2 May, 2015 @ 7:25am 
Originally posted by pasiltd:
Make that happen, and ensure that this is compatible with the Improved Public Transport and i can already hear the paypal link being clicked :)

You are right, with the way your work allows the lane management combined with the traffic light management, it would be just awesomely powerful tool to manage the traffic and by far the best mod to do that. Go for it! :)

Even if I make this happen, it won't be anytime soon as there's still a lot of work to do on my tool. I'm not making this mod for the clicks on the paypal link :)
#12
leftbehind 6 May, 2015 @ 5:08am 
Here is my use case for priority lanes (right of way / give way at intersections) in condensed form...

http://gtm.steamproxy.vip/sharedfiles/filedetails/?id=438241321

The green route across the screen (east to west) is much loved by my cims. They really want to use that road, despite my best efforts to convince them otherwise. The problem is, there's lots of intersections in close succession, and this causes traffic to dither when travelling down that road, eventually leading to BIG traffic jams.

I've tried pretty much all tools available to tame this road.

First, I tried creating a one-way system around my bus terminal - not only did that result in messy bus routes, it also didn't solve the problem - the intersections were still there causing traffic to dither. Then I tried lane restrictions, that too didn't work, it merely moved the problem elsewhere. I even built a road right over some mountains to give an alternate route, that also didn't work.

http://gtm.steamproxy.vip/sharedfiles/filedetails/?id=438241406

I customised the lane routings and that seemed to work, but ultimately it just caused massive jams in other areas and still a lot of traffic was determined to use the original road despite needing to take detours.
#13
leftbehind 6 May, 2015 @ 5:10am 
On the first pic above, the side roads (north south) are pretty much empty most of the time. Yet traffic flowing down the east-west road is dithering at each intersection along the way. If I could set that east-west route as priority lane, causing traffic to just drive straight forward without worrying about side lanes, it would solve the problem for me - and in such a way as to keep any side effects on the quiet side roads.

The only other choice I really have is to redevelop the road to remove most of the intersections, and I really don't want to do that.
#14
FretfulShrimp  [developer] 6 May, 2015 @ 6:34am 
My answer would be to change the roads - you could easily remove most of the intersections since the side roads are pretty much empty. Since you don't want to do that, let's discuss priority lanes and other options.

Have you tried using the traffic manager to set the priorities you want and did it really work as you expected?

Have you tried adding traffic lights? I know this sounds counter-productive but I read somewhere that lights change based on cars reaching the intersection, so my guess is that it would be green most of the time for the main road. If you haven't, give it a try just to make sure it's not an option.
#15
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