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Congestion view fixed?

Started by willyart, March 27, 2016, 08:06:44 AM

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willyart

I set up my to use what's called Duncan's logarithmic model (Equation 13) in this paper https://scholar.google.com/scholar?hl=en&as_sdt=0,5&q=evidence+for+speed+flow+relationships (see top google hit) to model the degradation in speed as roads get congested.  During the non-congested flow I kept a small premium in speed, as suggested in the following wiki article.  Here are my ultimate values:

Volume, value used
0.00,  1.2000
0.45, 1.1000
1.00, 1.00,
1.20, 0.8177
1.50, 0.5945
1.75, 0.4404
2.00, 0.3069
2.50, 0.0837
2.58, 0.0522

Seems to be working just as expected, I'm getting some interesting/awesome behavior from the modified traffic simulator.

Which brings to me to my question.  I assumed after reading the following article that my entire city would appear Green in the congestion display, with perhaps a couple of spots of Red in extreme cases (if I read the following correctly)

http://www.wiki.sc4devotion.com/index.php?title=Understanding_the_Traffic_Simulator

To quote the part I'm wondering about,

"Although the transition from green to yellow in the display normally happens right as the speed in this curve drops below 100%, if a speed value below 0.3 is present, the speed value is ignored, and the threshold for displaying a color other than green increases to somewhere above 100% of network capacity. The lower the lowest speed value is, the higher the threshold; if a speed value of zero is present, then the threshold is infinite, and the Traffic Congestion Data View always displays green everywhere, regardless of what the traffic volume is. Therefore, in order to have an accurate Traffic Congestion Data View, the lowest speed value should be 0.3.
Also, the volume number that is associated with a speed of 0.3 determines at what point the Traffic Congestion Data View shows the deepest red for a network. For example, if the lowest data point is (2.5, 0.3), then the Traffic Congestion Data View will turn the deepest red on any tile where the volume is at least 250% of the capacity of the network on that tile. For tiles with multiple networks on them, the Traffic Congestion Data View shows the congestion of the most congested network."

On the other end of the scale, a speed value of around 0.05 would seem to be appropriate, as this corresponds to heavily jammed networks in the real world. Unfortunately, there is a bug in SC4 that manifests whenever a point containing a speed value less than 0.3 is present in this property, regardless if such a point is ever reached in actual play. This bug manifests by distorting the congestion display."

However my display looks like I expected; roads at near or above capacity are coded such, I think.  It certainly isn't all green.  I though maybe I didn't apply my custom parameters successfully, but I doubt that because the traffic patterns dramatically changed to what I expected, right after apply the changes.

So is it safe to say the above discussed bugs in the congestion display fixed?  Maybe someone in the know can help...

Attachments:

- Graph of my customized congestion/speed values
- Screenshot 1: congestion
- Screenshot 2: volume

Tarkus

#1
Right now, your images don't provide enough information.  Namely, there's no quantifiable data included about what the capacity settings are for the different networks, or which version of the Traffic Volume DataView plugin you're using.  The numbers are necessary to make a complete evaluation.

I was involved with experiments regarding particular issue quite a number of years ago, when there was considerable debate about the traffic simulator settings and the Congestion DataView.  In late 2007, jplumbley designed a NAM Traffic Simulator plugin known as Simulator A, which used some values below 0.3 for the speed multiplier on the Congestion vs. Speed Curve.  The result wasn't immediately apparent to the untrained eye, but the effects of this change were that congestion was severely underreported when values below 0.3 were used.  It started to look as if congestion was based on the formula (morning+evening)/2, rather than the intended (morning+evening), as was calculated with the default 0.3.

-Alex

willyart

Ok the jury is out then; I'll delve into it but I have to do more basic tests as to whether the NAM road capacities are even being read by the game, I'm a little suspicious about that still, I'm unsure I did the installation properly.

b22rian

Alex,

i spent about an hour looking for this here-

QuoteIt started to look as if congestion was based on the formula (morning+evening)/2, rather than the intended (morning+evening), as was calculated with the default 0.3.

But just to be sure, the current traffic congestion view along with the other settings does have us with the intended formula of traffic congestion =  (morning+evening) commutes  ..

Is this correct  ?

thanks, brian