Topic: Understanding coverage, overlapping and connected stops/stations

[Bear789]

I'm in the process of starting my first Extended game (last time I played it was still called Experimental, and anyway it was years ago and several things have changed; anyway I honestly have a hard time remembering what was already in the version I played because at the time I mostly used Standard, so please forgive me if I ask questions about stuff I should actually know because it was in the game since the old days).

I can't help but notice that now the passenger stations coverage area is massive. I read in the feature overview topic that this is meant to work with the passenger walking feature, but it's unclear if there's any benefit in building other stations inside the coverage area or not (say, a feeder local line to some major rail terminal / port / airport). In Experimental you were allowed "street level transfers" which meant that two stations that were within each other catchment area would let passengers and goods walk and transfer between each other, IIRC, but I remember the coverage areas to be smaller. Is this still the case? Does this mean that if I build a stop/station inside the larger catchment area of another one, there are chances that passengers will transfer even if they are not intended to? Let's take the case of urban lines and an intercity terminal. I assume that if one urban line serves the terminal, passengers who need to catch an intercity train are smart enough to choose the urban stop that is actually connected or at least closer to the terminal, but what about urban lines that do not serve the terminal directly but nevertheless stop somewhere inside it's catchment area?

Also I have some doubts about how the size of a station affects transfers.
In Standard the only way to allow transfers is to connect all the platforms/bays/docks etc in a single station. Old Experimental had the aformentioned street level transfer. By the desctiption of it in the feature overwiew topic, it seems that the more stuff is attached to a station, the higher will be the transfer times between services.
Say that I have, again, urban underground platforms for a metro system and above ground platforms for intercity rails. Does this complex causes delays in transfers to all services? Say, metro commuters choosing this place to transfer to a service on the same platform are affected by the fact that there are several other platforms that are only meant for intercity travellers they shouldn't care about and vice versa? Does this mean that I'm encouraged to build the metro as a separate station and rely on the street level transfer feature for those who want to take any intercity service?
I choose metro because they are both rails services, so bonus question: does the same apply to intermodal transfers (bus to ship, rail to plane, etc)?

Thank you in advance for your answers.

[jamespetts]

Firstly, I am not sure when you last played, but this aspect of Simutrans-Extended has not changed significantly in some time - since before the name change from "Experimental". Street level transfers, as you term them, still work in the way that you recall.

The idea of the coverage area being large is this: a person can in principle walk quite far, and will do so if there is no other means of getting to where he/she needs to go. So, for example, in a medium sized town in 1850 with only a single railway station, people living on the periphery of the town may walk several kilometers from the periphery of the town to get to the station. 'Buses were rare in the 1850s (and in any event were only affordable by the middle classes), so this would be what one might expect.

However, all passengers have a journey time tolerance. This tolerance is different for each passenger generated. Walking, including walking from the passenger's starting point to the first stop, walking between stops, transferring within a stop, and walking from the final stop to the destination building, all takes time (on the basis of a speed of 4km/h travelling in a straight line). This time is taken into account when computing whether a journey falls within a passenger's journey time tolerance.

For example, suppose that, in the town in 1850 with a single railway station, a passenger wishes to travel to a building in a neighbouring town served by that railway. The passenger's journey time tolerance for the one way trip is 1 hour and 30 minutes. The train takes 30 minutes to complete its journey, and there is an average of 15 minutes waiting between each train. The station's internal transfer time is 2 minutes. Taking out of account walking, this would give a total time of 47 minutes - well within the passenger's journey time tolerance. However, suppose that the walk from the passenger's origin building to the railway station were 45 minutes, and the walking time from the station at the other end of the line to the passenger's ultimate destination were another 15 minutes. This would give: 45+2+15+30+15=107, or 1 hour and 47 minutes - in excess of the journey time tolerance. The passenger in that instance would not travel (assuming no accessible alternative destinations).

Similarly, passengers who are able to get to their destinations in multiple ways will always choose the journey with the lowest overall time. Again, this includes walking times and internal station transfer times. This might mean that a trip by 'bus which is nearly door to door will be preferred over a trip by a faster train where the better speed of the train is outweighed by increased walking times between origin and station, and station and destination.

This means that there are many situations in which it is beneficial to build stops within the coverage area of other stops: passengers will choose a starting stop based on whichever overall journey time will be the lowest.

As to the internal transfer times of stations, you can see this in the station details window. This is determined by the area of stations, and represents the time that it takes passengers to walk within the stations. This can be increased if the station is overcrowded. This does mean that there are situations in which it is better t have several neighbouring stations rather than a single, large integrated station. (For example, an airport can be split into multiple terminals, all sharing the same runways, each a separate stop).

To answer your final question, intermodal transfers are handled in exactly the same way as intramodal transfers.

I hope that this assists.

[Bear789]

All very clear now, thank you for the answers.

As I said I have fuzzy memories of the last time I played Experimental, however there's a topic-journal of my last Standard game, and it dates all the way back to 2013; I may be wrong after so much time, but I think I remember that when I started that map I mostly played it whenever I booted Simutrans (so it could be that I've not played Experimental since 2012ish, so it's really a long time).

[jamespetts]

Gosh, that is a while. Welcome back!

The idea of the Extended station coverage system is, in short, that one does not need to worry about coverage areas at all, per se, and one can just place stations and stops as one would in real life and expect more or less realistic consequences of doing so.

[wlindley]

Was there a discussion about goods transfers between adjoining stations of different companies?  I thought I had used that at one point, not sure what I am remembering.  The ability to build a goods railway station next to another company's seaport would make intra-line goods handling far more realistic, especially in technology transition periods.  I suppose that might only work if the "permission" checkbox in the company list were active... was that working on a branch or am I mis-remembering?

[jamespetts]

Goods being hand-carted between two different stops is not currently implemented. It seems to be a thing that might be worthwhile to implement at some point, but there is an extremely long queue of higher priority tasks at present and for the foreseeable future. If someone else were to volunteer to code it, of course, that would be another thing entirely: it would not be too complex: one would have to look at path_explorer.cc and modify the code for passengers walking to include goods (but make sure that they are carted at a quarter of the walking speed, and only within the much more limited goods coverage zone, not within the wider passenger and mail coverage zone).

[Bear789]

Speaking of coverage areas, I had the chance to look at some real life plans for a new metro line they're building in my city. I don't know if they were mere shiny pictures to entertain the laymen or actual engineering concerns, but when they showed the map of the route, each station had two concentric circular areas centered on them; the smaller one we could call primary catchment area in Simutrans terms, and showed the area considered well served by the station (meaning that commuters living in there were most likely going to use the new route if they were wiling to use public transport and if it was of any help for their journeys), and a secondary catchment area that could potentially be served by the station if commuters were willing to walk a bit more, or the station had some park and ride facility, or if there was some other local means of transport that can be used as feeder services, etc.

I don't know how much this would be feasible and how much it would impact the game and performance, but it could be neat to show something like that in Simutrans. A darker area of 2-4 tiles around a stop/station that is the primary catchment area in which passengers don't need any additional service and inside which you should put other means of transport's transfer stations, and a wider area, as big as the current one, where feeder services should be encouraged. I mean this as a tool for the player to plan their system rather than something that alters the passenger's behaviour.
Come to think of it (sorry if it's already in the game, as I said it's been five years since I touched it), it might be nice too to be able to individually display catchment areas when a station is selected (I mean, select a station, only it's cathcment area is shown and all the others are hidden).

[zook2]

If I've understood this correctly, there *is no catchment area* as such anymore:

"However, all passengers have a journey time tolerance. This tolerance is different for each passenger generated. Walking, including walking from the passenger's starting point to the first stop, walking between stops, transferring within a stop, and walking from the final stop to the destination building, all takes time (on the basis of a speed of 4km/h travelling in a straight line). This time is taken into account when computing whether a journey falls within a passenger's journey time tolerance."

Walking to/from a stop now simply eats up some of the maximum-journey-time budget. The longer a pax has to walk, the less likely he'll undertake the journey at all. But it also depends on the actual transportation speed you provide and on top of that max journey time is randomized for each pax. how far is too far is different for each one. The displayed catchment area is a bit of an atavism now.

[jamespetts]

There is still a catchment area of sorts, but it is retained for technical, rather than gameplay reasons (viz. that it would be too computationally intensive for every passenger to have to check distance to every station on the whole map, so it is limited to a catchment area). The catchment area is deliberately made so large so as to be of little real effect in the game compared to the walking time tolerances. This system is intended to simulate much more accurately the real dynamics behind what the idea of a catchment area tries to simulate very approximately.

Incidentally, as to park and ride, the long-term plan is to implement this properly (including station car parks), but that is a considerable way off, as there are a large number of higher priority tasks that must be completed first.

[Vladki]

If you click on a building you will see the walking times to station within catchment area.

In some other thread there's already a request for showing the walking times in minimap.

[jamespetts]

One might think of this system as akin to a catchment area with blurry borders.

[Vladki]

One might think of this system as akin to a catchment area with blurry borders.

I would think of catchment area as a hard limit on how far are pax willing to walk.

[zook2]

That's why the fact that it's still shown as a large rectangle is slightly confusing.

- First, it should be a circle (if I understand it correctly).
- Secondly, the outer limit of the circle shows acceptable walking distance for a passenger for whom the maximum allowed journey time limit has been rolled (almost none, because the random distribution is bell-shaped).
- Third, this walking distance is only acceptable if the journey time itself (plus in-station transit at start and ending stop, plus walking to the final destination building) is essentially zero. Every minute spent traveling, waiting at the stop (?) or walking to the final destination decreases acceptable walking distance and thereby the catchment radius.
- Finally, max. journey times are modified by distance to the destination (?). A pax might be willing to walk five miles to the airport when flying to Hong Kong, but only 500 yards when taking the bus to the dentist.

That's why I'd say that, essentially, there is no catchment area anymore. Which kind of begs the question how a new - or any - player should estimate a reasonable distance between stops.

[jamespetts]

It is important to distinguish between the actual, technical catchment area (as represented by the square) and the effective radius of a stop (which is not graphically represented at all, but one can consider it as a circle with blurred edges).

The technical catchment area is the area within which passengers will consider travelling to the station in question. It is retained in Simutrans-Extended only because not having such a catchment area would make the game run too slowly. It is not intended to have a gameplay function. Importantly, it is not in any way related to the passengers' maximum walking time tolerance.

The effective radius is (realistically) not precisely defined, and would be very hard to represent graphically in a meaningful way because of the inherently complex relationship between journey time tolerance, walking time to the stop in question and total journey time.

As to estimating a reasonable distance between stops: look in the buildings' information window. You will see the distance to nearby stops. A higher density population will justify a denser transport network than a lower density population (a city's overall population density can be seen in its information window, but some parts of a city will be denser than others). Look for stops with a large number of passengers registering as "too slow", even when the transport connexions are good. Use the passenger destinations feature on the minimap to see where passengers who are finding that their journey times are too long ("too slow") are originating, and consider increasing stop densities in those areas. Think about what would be a reasonable spacing between stops in real life in that sort of situation. There is no general easy answer to the question of how to set stop spacing - that is the point: one has to make interesting decisions.