In Simutrans-Standard, passengers prefer local destinations in early years, but less so in later years. There is a single "locality" factor which changes with time which determines that preference. Passengers are generated with only a single destination. Passengers are generated from any city buildings, and can be bound for other city buildings, attractions, and industries.
In earlier versions of Standard, passengers would have a roughly equal chance of going to any destination anywhere on the map. The effect of that was that the number of passengers who travel on a player's network increases exponentially with the number of different places served. With only a few places served, very few passengers will use a player's network. With a large number of places served, an overwhelming number of passengers will use the network.
In Simutrans-Extended, passengers are generated only from residential buildings, and can be bound for commercial/industrial city buildings, industries, attractions, player buildings (such as depots or signalboxes) or other residential buildings. Passengers can be either visiting or commuting passengers (the proportion of which can be set in simuconf.tab). Commuting passengers have different destination preferences to visiting passengers (commuting passengers never head for residential buildings, for example, whereas visiting passengers sometimes do). Commuting passengers head for buildings with available jobs; visiting passengers head for buildings with a visitor demand.
Passengers are instead limited by the journey time tolerance (see in detail below), but can have multiple preferences of destination so that if, for example, a passenger's first, second and third preference destination is not reachable at all or within the passenger's journey time tolerance, the passenger can head to her/his fourth preference destination building.
Note that the behaviour of this feature depends largely on settings in simuconf.tab.
The aim of this feature is to reduce the differential between the number of passengers that a player can transport near the beginning of the game and the number of passengers demanding to be transported when a player's network is large and well-developed, and also to make passenger demand more predictable and realistic.
In older versions of Simutrans-Experimental (as Simutrans-Extended was called at the time), passengers would prefer geographically proximate destinations, but this was found to cause distorted passenger generation, so it was replaced with the current system, which scales better and is more stable.
In Simutrans-Standard, passengers will travel anywhere, no matter how long that their journey will take. In Simutrans-Extended, passengers will only travel if the estimated journey time to their destination is less than those passengers' journey time tolerance.
The journey time tolerance is a semi-randomised figure, based on: (1) how far that the passengers are planning to go; (2) whether the passenger is a visiting or commuting passenger; and (3) a range of values set in simuconf.tab. If a proposed journey is longer than the passengers' journey time tolerance, the passengers will not travel, and will display "too slow" (similar to "no route") in the graphs of the stop that they would have used. The destinations of passengers whose journey would be outside their tolerance level is shown as pink on the passenger destinations map.
The aim of this feature is to enable players to generate additional revenue streams by reducing the travelling time between towns, and also to simulate the difference between actual and latent demand for transport, and the fact that latent demand will only materialise into actual demand in many cases when the travelling time is low enough. It should also make playing in early times, when only slow, low-capacity transport is available, more realistic, as only a number of passengers commensurate with the capacity of the transport networks of the day will be generated.
In Simutrans-Standard, all goods and passengers within a stop's catchment area (which typically fairly small - generally 2-3 tiles) go to any station/stop within that catchment area, based only on which station/stop can provide the route with the least transfers and intermediate stops to their destination. As noted above in relation to journey time tolerance, journey time is not measured or considered at all. Passengers will walk to their destination whenever the origin and destination is within the catchment area of the same stop, but never otherwise, however close the origin and destination are, and however much faster that walking would be than using public transport.
In Simutrans-Extended, the journey time, used for determining which route to take and the passengers' journey time tolerances, includes the time that it takes goods to be moved by hand (at 1km/h) and passengers to walk (at 5km/h; can be changed in simuconf.tab) from their ultimate origin to their origin stop and from their destination stop to their destination. At every transfer (where goods/passengers change from one convoy to another), a transfer time, based on the size of the station/stop, will be added to the journey time to represent the time that it takes to walk from one part of a station/stop to another, or the time that it takes to transship goods inside a station/stop. Passengers will always walk to their destination whenever the total journey time is within half their journey time tolerance and the overall journey time is lower than a route using a player's transport, but not otherwise.
This feature works best when the station catchment area is much greater than in Standard (8-12 tiles is recommended for passengers). Also in Extended, the coverage for freight is different than for passengers: by default, it is 3. This is to represent the fact that passengers can walk further than freight can be hauled by hand.
The aim of this set of features is more realistically to simulate the interaction between walking and public transport, to make the placement and size of stations significant in a realistic way, to prevent players from gaining an advantage by building one large station covering an entire town rather than building a local transport network, and more accurately to simulate the total journey time between the ultimate origin and ultimate destination, as well as to simulate the relevant differences in this regard between freight and passenger transport.
In Simutrans-Standard, goods and passengers find the route with the fewest intermediate transfers (changes) between their origin and destination. If there is more than one possible route with the same, lowest number of transfers, it effectively picks one of them at random. Passengers that can walk to more than one origin station will choose from which station to depart at random, then find a destination, then check to see whether they can get to that destination from that origin. Goods and passengers will always board the first convoy that will take them to where they are going, provided that there is enough space. Passengers not within reach of a stop will not walk to their destination however close that it is.
In Simutrans-Extended, the journey time for each route is calculated, and passengers and goods will automatically take the route with the shortest journey time. The waiting time for goods and passengers bound for each station at each station is also calculated and added to the journey time when calculating the shortest route, as is the time walking/being hand hauled from the passengers/goods ultimate origin to the origin stop/station, and from the destination stop/station to the ultimate destination, as well as the transfer times when changing between one convoy and another at a stop/station. The journey time and waiting time for each direct connexion from each stop is visible in the stop's detail window. The walking/hand hauling time to nearby stations is shown in city buildings' and industries' information windows. The transfer/transshipment time is shown in stations'/stops' detail windows. Where passengers are within reach of more than one origin stop, they will first choose their destination, and then see which, if any, of the origin stops within reach connects to their destination, and then choose to depart from the one with the shortest route (measured in journey time (including waiting time and walking/transfer time)) to their destination. Passengers who have not been waiting very long at a station will wait for the line or convoy with the shortest journey time, but will board anything that gets them to their destination if they have been waiting a while (how long that they will wait for the best line or convoy is proportionate to the likely overall journey time). Passengers will always walk to their destination if they are close enough. A side-effect of this feature is that it is now possible to see the origins of goods and passengers when looking at a convoy or station.
Note that one or two aspects (such as the maximum search depth) of this feature can be customised in simuconf.tab.
The aim of this feature is to promote realistic competition between different players, or even different forms of transport operated by the same player, and have goods and passengers use the network in a realistic way, requiring players to respond to the demand for the best route. Players can now take passengers away from other players by providing a faster route to their destination. This also incentives players to have a high enough service level to avoid overcrowded stations, as overcrowding leads to increased waiting times, and discourages passengers from using that route.