Janko
Janko Remember I am not a mapping specialist but I am a specialist in public transport information systems - and perhaps it is our different perspectives that triggers different views, and the terminology that we use. I am also guilty of using UK terminology which (for historic reasons) slightly differs from that used in the relevant European Standards that covers this area. If you simply use crow-fly proximity to determine whether an interchange is possible then you can quickly find situations where there are physical barriers river, buildings, ...) that prevent connections being made. If you determine proximity by routed walks then this requires a very detailed level of mapping to be available = and even then you might have two stops on opposite sides of a dual carriageway where the central reservation prevents pedestrians getting from one side of the road to the other. Furthermore, issues of road safety or personal security may mean that you would never want to offer a journey plan which uses a particular combination of stops as an interchange point. These are perhaps the key reasons why in public transport information systems the best practice is to define the members of an interchange location using what is termed a "stoparea" - which is a collection of stoppoints which generally will use the same public-facing name, and between which it is possible to interchange. When planning a public transport journey it is generally the case that the interchange time between stops in a stoparea are a fixed value - in the UK this is typically set to 5 mins - which allows for a short walk between two stoppoints within the stoparea plus a small time buffer in the event that the arriving service is slightly late. A station is a special type of stoparea in public transport information systems. Where interchanges involve a link between stoppoints which are physically separated by more than a modest distance (in the system I am involved in this generally would mean stops that are more than 150m apart) then, and only then, is a specific walk route defined for the interchange leg - in which case a specific walk time becomes part of the calculation for the journey plan. In the UK all of this forms part of the NaPTAN specification for stops - and this in turn is reflected in the European IFOPT standard, which is in the family of public transport information standards under the Transmodel reference data model. The key terminology difference is that in the European Standards a "Stop" is what I refer to as a "Stoparea" (because in everyday English a "stop" means an individual "stoppont". I hope this explains my perspective on what I have referred to as “stopareas”. Best wishes Roger From: Janko Mihelić [mailto:jan...@gmail.com] Sent: 03 July 2015 22:59 To: ro...@slevin.plus.com; Public transport/transit/shared taxi related topics Subject: Re: [Talk-transit] different interpretations of v2 PT scheme čet, 2. srp 2015. 16:32 Roger Slevin <ro...@slevin.plus.com> je napisao: I think you are falling into the trap of trying to cover too many things in one relationship. A stoparea to me as a public transport person is (defined functionally) a cluster of stoppoints at which it is possible to interchange between services – and as such it is also a collection of stops for which a single stop name can be shared (in the UK we then have a separate “indicator” to allow you to make the naming of each stoppoint unique within the stoparea. IMHO there is no sense in using a stop_area_group relation (You probably meant stop_area_group instead of stop_area) to show where you can interchange between services. That is already obvious if they are near each other, isn't it? Any two stops that are within ~100m from each other can be seen as an stop_area_group. You don't have to make a relation to tell you that. I see no reason to group objects in stop_area_groups, unless maybe if there is a name or ref that only makes sense to give to a collection of stops, and they all have different names. But if you are talking about a station, we have the tag public_transport=station. Janko Mihelić
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