First of course, Complex Traffic needs to be enabled in the gameplay options, either when starting a new map or during a running game. For me, there really was no noticeable downside even when activating it in one of my big existing playthrough, although depending on the busyness and layout of your streets, your mileage may vary. The reason for that is a slight change in how right-of-way is being handled.

Even once activated, it still remains a choice on how much you want to engage with the system. You can only add some traffic rules to a couple of important intersections, or plaster your entire republic in signs. The choice remains up to you.


These signs can be split into three categories;

• Regulatory signs
  
• Zones
  
• Priority Signs & Traffic Lights

All the road signs can be found under the waypoint in the Roads / Streets category.

Regulatory signs and Zone signs are both placed on the road. Priority signs and Traffic lights are placed on (or activated on) intersections.

Regulatory signs are signs you put on the side of the road, which passing vehicles are forced to abide by, or prohibits them from passing in the first place (more about individual vehicle traffic logic further down below). Most of the signs are self-explanatory using common sense and a basic understanding of real world traffic laws, but I'll still explain each and every single one of them in this guide and how they're used by the game's logic.

Regulatory Signs I would group into two categories;

• Segment Signs
  
• Restriction Signs

Signs need at least a gravel road or better, and can't be placed on mud road segements.
Two signs can be placed on top of each other. If for any reason you need more signs, you have to space them out. Further, placing one sign might overwrite another one. Placing a "No Motor Vehicles" sign on top of a "No Buses" sign, will simply overwrite the "No Buses".

Hypothetical example of a village's gravel road leading onto a bigger asphalt road:

The asphalt road has a speed limit of 90km/h and heavy trucks are banned from overtaking.
The gravel road has a speed limit of 40km/h, and only trucks that bring supplies are allowed to enter.
Pedestrians are not allowed onto the asphalt road, and vehicles wanting to go onto the asphalt road need to be capable of at least driving 50km/h.

Segment signs apply to the vehicle as soon as they pass the sign, and remain in effect for the remaining road segment.
However, this also means that a sign's rule is only being applied until the next node, as such these signs are only useful for longer road segments, and need to be "re-applied" for each road segment.



Maximum Speed signs enforce a speed limit on any vehicle that passes by. They can be used to make certain roads less attractive, enforce a more uniform speed by slowing down speedsters, or role-playing purposes.
The maximum speed can be increased and decreased by pressing E/Q (or whatever increase/decrease bridge height is bound to).



Vehicles are disallowed from overtaking any other vehicle. There's two versions of this sign: One that bans all overtaking of any vehicle by any vehicle, and one that only bans heavy vehicles from overtaking, but still allows smaller cars and similar to overtake slower vehicles.
This sign is useful to stop accordion effects from happening, where one vehicle (tries to) overtake someone else, forcing either the vehicle being overtook or one behind them to come to a full stop, which forces a following vehicle to also come to a full stop, causing a rippling effect for a bunch of vehicles and causing a small traffic jam.



Revert to default speed limit and allows vehicles to overtake each other.

Restriction signs are very straightforward; if you're not allowed to enter, you're not allowed to enter. And the republic's glorious remote-controlled autonomous GPS drone vehicles both obey all the rules, and know what's ahead of them.
This means both of these roads have the same result:

So while realistically restriction signs are at the crossroad and entrance of a street, in the game you can place it anywhere on the segment.
There are some special exceptions by some vehicles for sign rules, which I'll go into at end of this section.


Restricts all agricultural vehicles from passing; this means harvesting vehicles and tractors.


Restricts all heavy goods vehicles. This means any large open or closed truck, dumper, tanker and so on. Private cars, buses and others are allowed to pass.


Restricts all vehicles that carry some form of trailer, irrelevant of type. This means for example, the LZ 100 is allowed, but LZ 100 (trailer) and LZ 100 (semi-trailer) are both banned. Bendy-Buses are also banned.



Restricts all personal cars.


Restricts all buses.


Bans pedestrians from the road.
Unless there's some very specific situation where, for some reason, you want to ban people to walk somewhere, this sign is primarily for role-playing purposes, so pedestrians won't walk across your highway intersection.


These work like their standard counter-part. However, they allow vehicles that need access, to access.
Or to rephrase, trucks will try to avoid passing by this sign, unless they have to.

In this example, the W50 needs to head for the closer storage (green), while the LZ 100 heads to the further one (cyan). The W50 is allowed through the sign A, because the storage is directly behind, as such he's considered to be "supplying".
The LZ 100 is not allowed past sign A because the cyan storage is further away, even tho taking that road would be the faster route. So he has to take a different route. Sign B is also technically restricting access, but there's no other path to take, so he's considered supply and the sign allows him past (more on traffic logic further down).


Only allows vehicles that are below the designated weight. Takes into account current weight, not empty weight.

Can be decreased or increased with Q/E.
The direct use I've found thus far is very limited and esoteric, because one can just use the minimum speed rule to heavy and slow vehicles from a road. It seems primarily for role-playing purpose (e.g. designate maximum weight for certain bridges). But perhaps one could find a use for it in very specific and unique situations, such as filtering out vehicles with cargo and those without.


Only allows vehicles to pass, that currently have the capabilities to reach this speed. This means vehicles that are too slow because they're too old or too heavy or too full aren't allowed passed. A use for this is to keep busy highways free of slow moving vehicles that would slow down traffic.
Can be decreased or increased with Q/E.


Restricts any normal vehicle, this includes normal trucks, buses, personal cars and so on. Apart from just banning any normal vehicle from the street, could potentially be used to designate a street "pedestrian only", or to temporarily block off a road. Notably, the exceptions, described in the next section, still apply.

Exceptions

Certain vehicles are completely exempt from following all or certain rules. This means they are allowed past the No Motor Vehicles sign for example.

Emergency vehicles, like fire trucks and ambulances, ignore all traffic signs.
Utility vehicles, like Secret Police cars and technical service trucks (water, sewage, snowplows) ignore all restrictions, but do abide by speed limits and overtake rules.
Very small trucks, like the B1000 truck, or the Mcar 25, or the IMV 22, in general any truck or utility vehicle (e.g. roller) that's less than 2t, ignores all restrictions, but still abides by speed limits and overtake rules. The one restriction they do follow is the minimum speed restriction; so the one thing you can ban the Mcar 25 from is your fast roads.

Multicar gives zero ♥♥♥♥♥ about your laws

As mentioned in the Segmented Signs section, normal speed limit signs only apply to the current segment, and get forgotten by the next intersection or node.

Placing a normal speed limit sign in this kind of street is somewhere between impossible and pointless. But exactly for this there are zones.


Zones apply their speed limit to all the streets they encompass.

For them to work, the area needs to be properly enclosed.

The zone entry signs can be clicked on, to see an overlay of the zone, and see any potential error.

Even if a street is a one-way street leading away from a zone, the zone sign still needs to "point" at the direction of the zone.


There are two type of zones.

Speed Limit Zones

Speed Limit Zones force vehicles to drive below the designated speed limit within the zone. The limit can be decreased or increased with Q/E.

City Limits

City Limits is type of zone with a set 60km/h speed limit within its borders. From observation, it also seems vehicles will try to avoid driving through it, even if it's faster despite the 60km/h limit.
The City Limits zone is also very nice for role-playing, because they add really neat city limit signs at the entrance and exit.

Interaction with other signs

If placed within a zone, normal speed limit signs will temporarily over-write the zone's speed limit. Essentially, think of the zone as the new "default".
This means if the speed limit sign is higher than the zone, cars will speed up on the following segment. If the speed limit sign is lower than the zone, cars will drive even slower on that street. A "End of Restriction" sign, will only end the speed limit sign, and re-apply the zone's speed limit.

City Limit Zones and Speed Limit Zones can overlap each other. However, the speed limit zone takes precedent.

This means, you can have Speed Limit Zones inside of the City Limit Zone, and within that zone you can have even shorter normal Speed Limit signs.


"Yo dawg, I heard you like speed limits, so I put a speed limit on your speed limit, so you can limit your speed while limiting your speed"

Any intersection can be edited by simply clicking on it. However, the quality of the road limits the type of signage that can be applied.

Multiple crossroads can be combined into a larger crossroad. This is useful for if the space in between them would not make sense to have signage.

In the top picture, the truck is waiting in the middle of the street, because the 2nd crossroad's traffic light is red.
In the bottom picture, the two crossroads have been combined into a larger one, using the blue (+) sign. This results in the traffic lights being at more sensible spots, and the trucks are waiting at appropriate places.

As long as they are nearby, any number of crossings can be combined to a larger one.




Without priority signs, traffic obeys normal Priority To The Right, meaning any vehicle is required to give way to vehicles approaching from the right at intersections.


Any intersection that at least contains one gravel road, can have Priority Signs added to them.
Priority signs overwrite Priority to the Right. Each road is numbered and correlates to a number in the UI.
An intersection always needs two main roads. This unfortunately means one can not make 4-way stop intersections, although to be fair the reason for those existing in real life is to stop accidents, something that does not exist/matters in WR:SR.


Vehicles heading horizontally have priority. Vehicles coming from the south need to come to a stop if there's a vehicle on the priority road, but do not stop if there's no one else. Vehicles coming from the top need to come to a complete stop, no matter if they're alone or not.


Traffic Lights allow a better flow of traffic at dense intersections. An intersection needs to be completely asphalt. Further, if electricity is enabled in the game options, traffic lights need electricity. If there's no power, the intersection will fall back to priority signs, which also need to be set up for traffic lights.


The same four way intersection, with a basic two active green lights setup. The priority signs are still there, in case the electricity goes out.


A) Generate Pre-made template, where each road has it's own cycle. Only one light is green, all other lights are red. This means there'll be as many cycles as there are roads.
B) Generate Pre-made template, where each cycle tries to have two green lights. This means technically double the throughput, assuming no vehicles drive into each other. If there's an uneven amount of roads, the last cycle will only have one green light.
C) Manually add a cycle
D) Delete all cycles
E) Set all cycles to this length

A traffic light crossroad is made up of multiple cycles, each cycle being one "setting". Each cycle can have between zero or two green lights. After the interval, the traffic lights switch to the next cycle, until they're all done and it loops.


This example has three cycles.

• First cycle: The lights of road 1 and 3 are green, meaning the vehicles in both directions on the main road are allowed to drive. The north road (4) and the southern road (2) are both still red. This lasts for 15 seconds. After 15 seconds:
  
• Second cycle: The main road is now red (1,3), the north is still red (4), but the southern road (2) can drive. This lasts for 7 seconds.
  
• Third cycle: Now the north road (4) can finally drive.
  
• First cycle: North road (4) is back to red, south is red, main road is green again. Since the main road is supposed to have more vehicles, it's cycle is as long as the other two combined.

There's no limit to the amount of roads an intersection can have. There's also no limit to the amount of cycles an intersection can have. And a cycle can even be completely red, if for some reason you just want all the drivers to stare at each other.
One-way streets going off the intersection do not have and do not need lights.


I call this one "the driving instructor's torture weapon"

The game's vehicles obey one rule:

• Find the fastest route I'm allowed to take

Vehicles don't care about anything else. They don't care about distance. They do not care about road type. They do not care about traffic.
Further, they only take into consideration their current maximum potential speed. This means, if some truck is fully loaded and can only drive 31km/h, it does not care if route is a mud road, a gravel road or a high speed one-direction asphalt highway; it only cares if it's allowed on them and if it's the fastest. A vehicle also always has perfect knowledge of what's ahead and knows the entire route and knows which roads it can take and what their speed limit is.

Example:
A mud road has a "natural speed limit" of 30km/h. The asphalt road allows faster driving speed, but takes a longer route. The large BZ 252 Dumper has a max speed of 35km/h, so the asphalt road gives him little advantage, and the shorter mud road remains the fastest path. The MZ 104 bus can reach a speed of 80km/h, so even tho the mud road is technically shorter, staying on the asphalt road where the bus doesn't need to slow down, remains the faster route.


Follow up:
The mud road has been upgraded to an asphalt road, but has a 40km/h speed limit. A third road has been added, which is technically shorter and has no speed limit, but does have an intersection with traffic lights.
The BZ 252 Dumper doesn't care about the 40km/h speed limit, and still takes that route.
Without the speed limit, the MZ 104 bus and W50 truck would also take the shortest road, but even tho 40km/h is faster than the mud road, that road is still slower for them and they chose to avoid it. The MZ 104 and W50 could take the new middle road, but the traffic light is unattractive and is a form of slow-down, so they continue to stick to the outer most road, which remains to be the fastest route for them.


This means if there's for example two roads to it's destination, one going through a town with a 60km/h speed limit zone and even some 40km/h parts, and another road that goes around the town but has no speed limit, most vehicles will figure out going around the town is actually faster. Unless of course, we're talking about our dumpy big fat truck from earlier, the one that can only drive 35km/h anyways. In it's case, it might decide to just drive through the village. To prohibit that, one would also need to put "No Heavy Vehicles except Supply" at various parts of the town, potentially even at the entrance of it. Or one could put a Weight Limit sign in front of the town.

The point is that the toolbox is large and diverse enough, that the same problem can be solved in a bunch of different ways. Most of it can be figured out through experimentation.

Like much of this amazing game, there's no "one correct way" to do things.


Now what can and should you do with it?
Well... that's really up to you, and the specific problems you are looking to solve at any given time and location.

Traffic lights are great at directing traffic, but a waste of time and electricity on a random rural road that only has one single random truck drive by once every 40 minutes. Even priority signs might be unnecessary in that situation.

At the entrance of a busy industrial area, you could have 3 separate roads leading into it. One for buses and private cars bringing workers, a separate one for the empty trucks, and one for the fully loaded trucks. The car/bus road could have "Heavy Cargo trucks" banned. The road for empty trucks could have a "Weight Limit" of 7t, which is exactly the LZ100 dumper semi-trailer truck, meaning any one of those with a full load would be banned from it. And the road for the full trucks, could have the "No Overtaking" sign alongside a "Speed Limit" of 50km/h, so the heavy fully loaded trucks are left alone and not interrupted.

(Looking at it, one could even further optimize it by switching the two truck roads, since the empty ones are crossing the path of the full ones. Further, in this screenshot, there are no full ones heading towards the area and leaving empty)

You can have a large downtown area, which is part of a Speed Limit 40 zone, but has one large road going through it with a speed limit of 70. Meanwhile, all the side roads have the "No Heavy Cargo except Supplies". And also, pedestrians are banned from just walking all over the fast road, and instead are told to use the safe bridges.


You can have one Distribution Office take from two different cargo station, one of the two is exclusive for smaller trucks, while the large trailer trucks are bound to the other one. This means the two types of trucks won't clog each other up when picking up goods, but they're still part of the same distribution office and can deliver to the same customers. This could be done by having one cargo station access road have a 5t Weight Limit or restrict trailers, or both. Then have a 30km/h speed limit on the other one, just to make it even less attractive for the small trucks' pathfinding.


Tip:
Signs can't be placed on bridge segments, however they can be placed on the nodes in between segments.

Similarly, signs also can't be placed on mud roads, however this can be circumvented by forcing nodes onto them. This is easiest done placing down a road, and then deleting that segment.




If you can think of any other interesting ways to use the traffic toolbox, do not hesitate to share it.