Congestion Causing abandoment, even with "Short" commute time..

[westamastaflash]

I'm using traffic Simulator Z 2.2 (High) with CAM. I have an avenue leading to my industrial area, and the road is *very* congested ~ 12000 cars. The "Congestion" view shows it as red. However, when I query a house that is sending traffic to the factories, it says "short" commute. At some point, The traffic all disappears and the same house now has a "no job" zot and says "Abandoned due to commute time".

I thought that congested roads had a set minimum speed so travel always occurs. It seems to me that once the road is too congested, *everybody* starts to abandon their homes.

Unless there's another factor here that I don't know about. I'm a relative newbie when it comes to trying to balance demand and education and such, so I'm thinking that maybe something else is wrong.

The city seems to grow fine, then all of a sudden there is massive abandoment. I can provide more details, I'm just trying to understand what's causing these "long" commute times. The Census Facility says that I have 37,000 available jobs, and my R$,R$$,R$$ bars are all very high. But somehow the simulator isn't "re-checking" the log commute? It's all on one city tile, just some RHW and avenues.

[RippleJet]

If the distance to work is short, the reported commute time may very well be short, even along a congested avenue.

I thought that congested roads had a set minimum speed so travel always occurs. It seems to me that once the road is too congested, *everybody* starts to abandon their homes.

If the road becomes too congested, the pathfinder will simply not choose that route, and will start looking for alternatives.
If none are found, you will experience mass abandonment.

I can only suggest that you either build more roads/avenues, or add mass transit (buses and/or subways).

[westamastaflash]

Ah. Thanks - I did only have one route to my industries. I solved the problem with an GLR line (of course, I'll need to make sure it doesn't become congested too).

[z]

If the distance to work is short, the reported commute time may very well be short, even along a congested avenue.

Within a single city, using Simulator Z, all successful commute routes are classified as short.  (This is not something that is directly adjustable in the simulator.)  All commute times to other cities are long.  You can get medium or long commutes in a given residence if you have a mixture of short commutes and commutes to another city, or short commutes and failed commutes (i.e., unemployed Sims), which are classified as long commutes.

If the road becomes too congested, the pathfinder will simply not choose that route, and will start looking for alternatives.  If none are found, you will experience mass abandonment.

I can only suggest that you either build more roads/avenues, or add mass transit (buses and/or subways).

This part is incorrect.  If the pathfinder doesn't find shorter alternatives, it will choose the congested route.  (In Simulator Z, the only time the pathfinder fails is if the destination finder guessed wrong and no valid path exists to the destination.)  That's why you can use Simulator Z Classic in a city of many millions and not get mass abandonment.  But building more roads and avenues or adding buses probably will not help the abandonment problem, for reasons described below.

I thought that congested roads had a set minimum speed so travel always occurs.

That is correct; for this reason, as I have detailed elsewhere, all networks actually have infinite capacity.

I solved the problem with an GLR line (of course, I'll need to make sure it doesn't become congested too).

And here you have discovered another secret of the traffic simulator.  Although all networks have infinite capacity, the destination finder rules out various routes before the pathfinder even runs unless there is sufficient rapid transit.  GLR counts as rapid transit; buses do not.  Since GLR is rapid transit, you will find that it is possible for it to get quite congested without causing abandonment.  The main point is that your GLR routes need to be located where they're needed.

You can find many more details about how this all works in A Guide to the Operation of the Traffic Simulator.

[westamastaflash]

Thanks for clearing that up Z :-) I had actually tried adding buses first to no avail. Based on my reading of your other posts, buses don't actually reduce congestion, they just serve as a way to move people from mass transit hubs to local stops or local mass transit.

[z]

Maxis left us with a Hobson's choice - we can either treat buses like all other vehicles, meaning they're single-passenger and contribute to traffic like cars, or we can have them not contribute to traffic at all, which is what earlier simulators did.  This latter choice was largely necessitated by the limits of pathfinding in previous simulators.  But although having single-passenger buses is far from ideal, it is still better than the other alternative, since when buses don't contribute to traffic, the traffic simulator will just stuff more Sims onto buses whenever congestion occurs on any network.

But buses are useful for more than just ferrying passengers to and from transit hubs.  The player has a fair amount of control over where the buses go, and since a certain percentage of Sims prefer using mass transit, it is not hard to direct a fair amount of traffic past businesses.  Having additional road traffic increases the desirability of these businesses, which increases the likelihood that Sims will actually go to work there.  So buses can be a very powerful transportation tool, even if they don't relieve congestion.