Table of Contents
Gridlock is a nasty thing. If vehicles get stuck, sometimes blocking each other, the player has to manually intervene. Luckily, using intelligent techniques, such situations can be minimized, ideally avoided. On large heavily connected transport networks, gridlocks are a real nightmare.
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Station coverage area is the area, that a station covers. This means, only passengers and cargo within this area get transported. Simple bus stops cover one field at each side. Double stations increase their area on two fields on each side. To have an effective traffic flow and maximum revenue, use stations of the adapted size, and place them on strategically points. Also the number of stations count. It is not advised to use stations, which coverage area overlaps. It is much better to use hub stations layout instead.
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It matters very much which vehicles are used. While some players might like the variety of numerous different vehicles offered by Simutrans, you must comprehend that mixing vehicle types does not match the reality. In the reality one transport entrepreneur also has ONLY few vehicle types. The simple reason is the cost of spare parts, and the same technical details. It is much cheaper to service the same of manufacturer vehicles. The different speeds and power different vehicles have in game, may also be taken in account, because slower vehicles may obstruct the quicker one, because the quicker one must follow the slow ones. One must find a balance between vehicle variety and transport performance. It is important to use the adapted number of vehicles. To few make the source station to crowded, and to many make loss instead of profit.
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When there are many vehicles in a traffic grid, either road or rail, and the traffic grid is to short to accommodate the vehicles, lockouts may occur. The vehicles lockout each other, making a gridlock, and the traffic flow is stopped, making losses, instead of profit.
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Ships are better used, when there is an optimum number of vehicles, or a heavy congestion might occur. While overtaking makes the most sense for road vehicles, it would be good to have one day an AI , which uses overtaking also for ships instead of queuing. It would be ideal, to queue the ships with same speeds, and let overtake the quicker the slower ones. This would be realistic. Nowadays, they can go one through the other, this will so not cause a jam in Simutrans.
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Road network can also become crowded.
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The only help can sometimes be, if the vehicles involved in the jam are NOT YOUR OWN ones, to destroy them. This is done by using the destruction tool. Sometimes, a multiple click on the same spot is necessary. For your own vehicles, send them to depot, they will ignore all obstacles.
As of now, the overtaking is not implemented properly. In fact, it is not implemented at all. For road vehicles you may use a simple technique for overtaking. While it is "unofficial", it does work. This technique implies using the minimum speed signs and optionally one-way roads. Currently, real overtaking is not implemented, and is likely not to be implemented, because of the difficult implementation in the game engine.
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If traffic becomes really heavy, one option is a semaphore. It does regulate the traffic flow by traffic lights, so clearing and preventing a traffic jam. Semaphores work on the principle of letting only one direction true, blocking the vehicles coming from left and right, and passing straight, left and right. After a phase, the semaphores switch again, and leave the blocked direction, and block the other. And so on...
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Like in the real worlds, one way roads maximize the road vehicle flow. The road vehicles are only allowed to use one way of one-way roads. Trams, which may run in the middle of them, do not use the rules. They have their own management, just like in the real world. One-way roads may be used as a pure one-way road, or a combination of two quasi-parallel roads, each a one-way road in the opposite direction. Parallel one-way roads are typically used to maximize the traffic flow. Traffic will still only use one lane of travel, and cannot overtake. The other is not used, due to game limitations.
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Tunnels have quite some advantages. They shorten a route, and make an extra path. While more expensive at first, they do pay off very quickly thought the traffic flow.
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A highway is basically a combination of two one-way roads. But the speed is within borders, meaning vehicles which cannot reach a certain speed, may not use the highway. This is also how highways in the reality work. Highways are usually the roads to two or more big regional hub cities. Because of the minimum speed restriction, the traffic is distributed quicker. Only one lane of travel is used, due to game engine limitations.
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Some roads can also be closed, to make a decoration for your road networks, or simply to clear out gridlocks, or only temporary when you build something. In fact, in the real world, streets are only closed temporarily.
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If the gridlock happens due to traffic congestion, and it is a simple crossing, the solutions is to simply place signals on this crossing. Vehicles will take alternatively the route and so hopefully clear the gridlock.
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If the gridlock is not solved through a semaphore on the crossing, try sending your vehicles in the gridlock to depot.
On frequent crossings, the ways to traffic congestion is through building of advanced crossings.
If not possible, go through the vehicle route assignment and send the vehicle to another station, it is supposed to go later.
In case of a heavy gridlock, simply try to place a depot near a crossing, and send the blocking vehicle(s) to that depot. As soon the congestion clear, start the affected vehicle again. It will simply resume, where it last wanted to go.
The fact that a gridlock happened, should ring the bells. There is some misconception in the network!
If the gridlock is due to a large number of low capacity vehicles, decrease the number of vehicles, but get vehicles with a larger capacity.
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To prevent future gridlocks, if the gridlock is caused by normal traffic, which is not under your control, some traffic control must be done, either by making a two way road in a one-way, or using the semaphores. When there is much traffic pressure between two residential area , maybe it is time to consider placing the minimum speed sign, and/or making the street into a four lane regulated one. And soon, the traffic flows much better.
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Any traffic making problems, may be removed by removing the street part with the congestion.
In order to prevent gridlocks at all, previous planning must be made carefully. When there are to few streets and to many vehicles, the gridlock will happen.
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So, the most obvious way to prevent it at all from happening, more parallel roads are necessary. Either 4-lane roads, from which everyone is one-way, or parallel roads, to which the traffic distributes. Road traffic distribution is crucial, in order to avoid a gridlock, especially in dense urban areas.
Another way is to build a roundabout. A roundabout is a circle, where vehicle passes in one direction, in order to speed up traffic flow.
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An simple roundabout can be achieved in Simutrans by using one-way signs. In real life, most roundabouts do not have any signals. However, if the traffic congestion is really great, then the combination of traffic lights and roundabouts is used.
Rails offer a capacity boost in comparison to road networks, but they cost more. While it is possibly to make a profitable traffic company only by trains (first fully artificial man made vehicle is a steam locomotive), if you like to get profit quicker, it is better to first create a profitable road vehicle route, and then combine road and rail networks, and eventually shorten the route, or make a hub station layout. That way you can get the best results.
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Signal blocks are separate sections of a rail, which have the possibility to hold only one convoi at a time. They are produced by placing signal on a track. The signal has a direction, or is bidirectional. Behold the bidirectional signals! Use the bidirectional signals only in one case: when this is a railroad with only one track, and only one vehicle is supposed to use this railroad. Otherwise, the gridlock is here in no time. Unidirectional signals are good for increasing the capacity of a much congested parallel leading railway track.
By building rail blocks, it is very important to build them long enough, meaning that the longest train, that is supposed to pass the route over a particular signal block, is shorter than that particular rail block. It is possible to mix the length of signal blocks, shorter and longer ones. In this case, the longest train convoi, that passes the succeding signal blocks, should fit, but also this succeding signal blocks can accommodate a few shorter train convois.
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To maximize rail traffic, you may use different rails, physically leading to different destinations. It is advisable, to balance the traffic, meaning, due to way finding, the trains will chose a particular rail leading from a crossing, only if it is the shortest way to it's assigned destination station. Here does matter very much, that the signals are used the right way. Only one, accidentally wrong placed signal, can bring the traffic on the whole track to a hold. And profit sinks.
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The depot (road, tram and especially (mono)rail) is, of course, the place where you buy your working vehicles and take convois together and apart. The depot is much more. It can be the best friend, which helps in a gridlock. A train which is stuck in a signal block, can be sent to the depot, and make place for others. The command to send a vehicle to depot ignores any signals, and is thought to be emergency tool for clearing gridlocks. There is a bug, which blocks crossing sometimes. Sometimes, when a rail convoi enters a depot, it does not clear a crossing. You have to do it manually, by using the blocktool. Funny that this bug still exists in this version, and has not yet been fully repaired.
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If there is not a simple way to achieve this, try clearing a signal, a train will go through other and hopefully clear the path.
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If not possible, go through the vehicle route assignment and send a train to another station, it is supposed to go later.
In case of a heavy gridlock, simply try to place a depot near a crossing, and send the blocking convoi to depot. As soon the tracks clear, start the affected convoi again. It will simply resume, where it last wanted to go.
The fact that a gridlock happened, should ring the bells. There is some misconception in the network conception!
All signals should be checked:
Are the unidirectional pointing to the right side ? If no, correct the wrong ones.
Are the bidirectional only there, where necessary ? If not, correct immediately.
The length of ALL the signal blocks, leading from this crossing in every direction, until some other crossing, must be checked. Is this the cause ? If possible, increase them, or shorten them, depending on the length of passing convois.
Was the cause some train(s), that took a route, you did not participate for it, but the AI thought it is quicker? If yes, place a waypoint in the route order or vehicle order (respectively, depending on circumstances).
Do some trains in this gridlocks have a wrong route assignment ? If yes, correct immediately.
The gridlock WILL happen again, if nothing is done... Either the number of train convois has to be reduced, or the tracks need to be made longer, to accommodate more signal blocks, so more trains can pass, without blocking each other out. One solution is also to use the concept of hub stations.