If you should be bored a bit from reading the first part of the User's Guide, it is considered as a nice change to follow now some of the examples. As the game value of a graphic simulator is quite high, please forgive the author to lead you sometimes to non-scientific examples, and suggesting you to play with the topologies instead of doing pure research on traffic control.
4.1 Useful SituationsHere some situations which you might not know how to define right away (you can find them all in the project "USEFUL.TCP"):
 | A bus stop: define a bus stop by giving a time-out to a block. In the example the time-out is 10s: |
| Lane changing vehicles: the bifurcations use probabilities of changing between different lanes: |
| Uncontrolled turns on an intersection (i.e. a right turn which crosses opposite straight ahead traffic): use a block which represents the street segment which is checked by a car driver before turning on the intersection. If this segment is free, the car can drive away, else not. |
| Slower trucks: generate trucks (using a "T"-command for "trains", but who cares) and apply a maximum speed to the generated vehicles. |
4.2.1 Half a Japanese Intersection
Japanese intersections can control right turns by a
right-turn arrow under the traffic light. If this arrow is not illuminated, right turning
traffic may drive over the intersection if the opposite lanes are free. The button
">" controls the right-turn arrow.
4.2.2 Heimplatz
The Heimplatz is a square in Zürich, Switzerland. The author used the example of this square to demonstrate the adaptive control algorithm in his thesis. Therefore, such a classic example must not be missing at this point... The following special constructions are used:
| Cars are routed according to probabilities. |
| There is a trolley bus (31) on the lower street with stops in both directions on the side "Kunsthaus". |
| "Stop Hottinger", where the two stops of streetcar number 3 can be found, uses a timer for delaying the streetcars. Trains bound to the right side (towards Hottingerplatz) have to respect an additional signal before leaving the stop. |
| If a stop is on the other side of the intersection, the streetcars can only drive on if the stop is free. |
| Streetcars coming from the side "Hottingerplatz" switch a bifurcation according to the detected ID. |
| Streetcars coming from up from "Bellevue" are routed after the stop according to their ID (without an explicit switching). |
Do you want to play a little bit? – Yes? – Ok, let's build a model railway. Draw two railway stations, one on the top and one on the bottom of the screen. Secure all exits by a signal (use pedestrian signals as they don't have an amber light and set the amber time and the red-amber time to 0). Connect the two stations by a single non-directed street so that the trains can circulate in both directions.
Now draw the garages: from the left there shall come a blue train with 6 cars and from the right a red train with two times two cars. Do you remember how to send the code to the source point? Because train drivers are very awake, set the wake-up time of the trains to 0, so that they drive immediately away when the signal switches to green.
Before you start simulating, check the positions of the switches: make sure that the trains coming from the one-way access of the switch drive towards the two-way street and don't circle around in the station! There is no need for changing the position of the switch then.
Railway, model 1
We want to improve capacity of our transportation system by adding more blocks, so that more trains can circulate simultaneously. Split you station tracks in two segments, add also a signal for trains coming from the garage, and secure not only the exit from the station tracks, but also the access to the station tracks. These signals operate on non-directed lines: make sure that the street block is the ending point of that line on which you want to be able to block the train.
Railway, model 2
This was nice, but manual labor is very expensive: so lets look for possibilities for automating our train system! – We have to add real blocks for knowing if a segment is occupied by a train or not. Use the block-elements and configure them as short blocks because one train might be longer than the block segment.
Except for the bi-directional parts of the tracks, you can make the signals switch automatically by connecting the block output points to the signals. The exit signals of the station must switch back to red when the train passes them. The point where the trains from the garage enter the system is still somewhat dangerous.
Railway, model 3
We should now seriously think about the bi-directional parts. Let's implement a first-come-first-serve strategy Do you remember the state machine we constructed when we were introducing the gates? – Use now two of these state machines, one for each bi-directional segment of your railway system. Don't forget to remove the translators, as the switching of the exit signals will now be controlled by the two state machines.
Railway, model 4
