[pierreh]

Today I have good news and not so good news.

First the good news: the strange abandonment of residences, and to a lesser degree of commercial buildings, in Marlande, about which I reported recently, has ceased. In the last playing sessions of that city, residents have returned, to the point that the current number of inhabitants in that city is higher than ever before. I didn't do anything to cause either the abandonment, or its reversal, I let the city 'play itself', with no intervention, other than monitoring and fixing subways (see below). Of course I am not the wiser, as to why the abandonment happened, and why it ceased. For the moment I'll consider it as a fluke in the game play. If it occurs again I'll try to look into things in more detail.

Now for the less good news. It has to do, to no-one's surprise, with regional playing and inter-city traffic between 2 cities: one of these cities is Marlande, the 'abandonment city'; the other is Desognes. I think that I have already mentioned in this CJ (a long time ago) that I am using the 'Ultra-Euro-Custom' version of the traffic simulator. )n the famous tutorial "Understanding the Traffic Simulator", we find the following note about subways:

"In deciding whether a job is reachable from a residence with the current traffic simulator settings, the destination finder weighs the presence of subways very heavily, especially subways that go very near the residence, and presumably, those that go near the job as well."

And about mass transit in general, the tutorial contains: "Perfect pathfinding results in much higher mass transit usage, which means less road traffic in general.". 'Perfect pathfinding' is defined in detail in the tutorial; the value of the Pathfinding heuristic property that produces perfect pathfinding is 0.005797. That value is used in the simulator I am using.

As already documented, I implemented, in a gradual fashion, inter-city subway links between the cities in my clusters. In the particular case of the inter-city traffic between Marlande and Desognes, there are at present no less than 11 inter-city subway lines (one of which being in fact a line that passes thru Marlande to reach Arcens).

What I'll document here, and what bothers me a lot, is the discrepancy between the number of travelers in the subways, reported at the respective city borders. I'll show here the 11 inter-city lines, seen in both cities, with the numbers shown in the traffic queries. Desognes in on the left, Marlande is on the right:

For the 2 lines above, Marlande reports over 60% more travellers.

For the 4 lines above the differences are less than before, but the numbers reported in Marlande are systematically higher than those reported in Desognes. The 'highest' line in the picture is saturated in Marlande.

For the 2 lines above, Marlande reports 2.2 times, respectively 3.3 times more travelers than are measured in Desognes.

Finally, for the last 3 lines, the discrepancies are even greater: two lines that show modest traffic in Desognes are both saturated (!) in Marlande, and for the 3rd line it is the reverse: that line is saturated on the Desognes side, but not on the Marlande one - in fact, this is the only line where Marlande reports less than Desognes. It is also the 'pass-thru' line to Arcens.

I never expect that numbers will jive exactly, since cities can't be played simultaneously - there is always a delay effect. But in my previous observations the differences between both sides of an inter-city subway link were rather minor, on the order of a few percentage points. Here we have major discrepancies.

Well, I must live with that, since I intend to forge ahead with the development of the cluster. I'll concentrate presently on the situation in Marlande, where the highest numbers and most saturations are found. I need to determine where Sims reside and where they work in the other city (traffic goes both ways), rearrange the lines, possibly dismantle 'weak' lines, beef up where there is saturation, and so on. That work has already started, but since it involves additional links to the neighbor cities, I’ll have to play those to get the inter-city traffic to adjust itself. Plenty of work to keep me busy....