5 ms·

Incidentally, the zone system for the Danish public transit system is not a metric space. (The ticket you need from A to B is not necessarily the same as from B

by sshine 8y ago

Incidentally, the zone system for the Danish public transit system is not a metric space. (The ticket you need from A to B is not necessarily the same as from B to A.) That's a kind of practical graph where you want efficient shortest path algorithms for.

deleted 8y ago
[deleted]
gumby 8y ago
Really?? Is that true only when there are multiple paths between A & B or is there something else involved?
- CydeWeys 8y ago
  Other possibilities: Trains going in different directions don't make the same stops (express vs local), and time-based fares applying to a specific direction based on commuting patterns. In the US, on Amtrak, a ticket is specific to an exact train, like buying a plane ticket. There's no generalized "I want a ticket from DC to NYC."
  - bunderbunder 8y ago
    Some of the shorter ones have unreserved coach class tickets that aren't restricted to a specific train. So, while there is no generalized, "I want a ticket from DC to NYC", there is a generalized, "I want a ticket from Chicago to Milwaukee."
- bunderbunder 8y ago
  Chicago has a minor version of this, even without zone fares: The entry fee to get on a train is $2.50 everywhere except O'Hare Airport, where it's $5.
  - gumby 8y ago
    Interesting, thanks!
  - notyourwork 8y ago
    The tourist fee.
    - bunderbunder 8y ago
      Nah. Most the people I see on that train are people commuting to/from work, and locals who live along the blue line corridor. Some tourists, but I think most of them are opting to pay a driver 8x as much to take even longer to get them downtown.
- tzs 8y ago
  Another possibility is that there is more demand in one direction. You might have a major city, A, a center of finance and law and full of corporate headquarters, and a smaller city, B, where many of the companies whose headquarters are in A have their engineering and manufacturing facilities. Someone making a deal with one of those companies may need to visit both engineering to work out technical details first and then visit headquarters to work out business, financial, and legal details. They will travel from home to B, and then travel to A, and then when done travel directly home from A. This may happen much more than the other direction--people needing to visit headquarters first and then going to visit engineering and manufacturing, without needing to go back to headquarters. Net result: more passengers needing B to A than A to B. This can result in A to B trips having empty seats. It might even result in some trips with no passengers at all! They can't simply cancel those trips, because they need to get the vehicles to B to handle the B to A traffic, so they sell seats cheap.
- Lewton 8y ago
  They use a zone system, and you don’t have to pay for a zone if you get off at the first stop after entering it. This creates the asymmetry
  - gumby 8y ago
    thanks
- sshine 8y ago
  For busses, the B stop on the way out may be in another zone as the B stop on the way back because they're geographically displaced. For busses and trains, depending on your type of ticket (2-8 zones, 8+ zones, commuter card) and whether the zone intersection is on or between stops/stations, you may have to pay for that zone one way but not the other. Those are edge cases. But the most confusing part is the ring topology (here shown with the zone-ring center being the actual city center): https://passagerpulsen.taenk.dk/sites/default/files/styles/full_width/public/zonekort_movia_hjside830x400.jpg https://passagerpulsen.taenk.dk/sites/default/files/styles/f... When buying 2-8 zones you don't pay for individual zones, but rather rings from your origin zone. Going one way, the zone rings look one way. Going back they look different, because the origin zone is different. A practical example of this peculiarity: You go from Hellerup (zone 2) to Friheden (zone 33) via the central station (zone 1). Your ring 0 is zone 2, and zone 1 and 33 are both in ring 1, so you only pay for two zone(-ring)s: https://dinoffentligetransport.dk/media/1413/svanemollen-friheden.jpg https://dinoffentligetransport.dk/media/1413/svanemollen-fri... You go back from Friheden to Hellerup via the central station: Your ring 0 is zone 33, zone 2 is in ring 1, but zone 1 is in ring 2 this time, so you pay for three zone(-ring)s: https://dinoffentligetransport.dk/media/1411/friheden-svanemollen.jpg https://dinoffentligetransport.dk/media/1411/friheden-svanem... Your origin zone on the way out was adjacent to both other zones needed (needing only 1 ring), but your origin zone on the way back was not (needing 2 rings). So they're not just different prices: The graph that spans train stations via zones in the ring topology is not metric. So getting a return ticket is not the inverse of getting the ticket out. And while you have a ticket that's valid for the timespan of your return, it may not be valid for your return path.
  - deleted 8y ago
    [deleted]
  - ZeikJT 8y ago
    What the... that was painful to read and comprehend. Was this kind of complexity really necessary? Did someone get a promotion for coming up with this?
    - sshine 8y ago
buckminster 8y ago
The rail network in the UK is also strange. On some routes it is cheaper to split your journey across multiple tickets. On others it is cheaper to buy a ticket for a longer journey. However, this is illegal and the train companies do attempt prosecutions.
- saganus 8y ago
  Why is it illegal and how do they enforce it? I know that something similar happens with airplane tickets but they get you with the luggage and with terms & conditions AFAIK. How is it similar/different with train tickets?
  - buckminster 8y ago
    It is illegal because the railway byelaws make it illegal. The railway doesn't just have its own law, it also has its own police force, The British Transport Police, though as far as I know they don't do the ticket enforcement. You are not allowed to break a journey either, so a ticket inspector can spot a ticket for a longer journey at one end of the other. The multiple tickets ruse is more of a grey area.
    - DonaldFisk 8y ago
      BREAK OF JOURNEY Rules vary by train company and route. In general you cannot break your outward journey (except for necessary changes of train) but you can break your return journey. Source: https://www.splityourticket.co.uk/info/fare-types.aspx https://www.splityourticket.co.uk/info/fare-types.aspx I've already dealt with the legality of split ticketing in another post.
      - aaaaaaaaaab 8y ago
        And how do they enforce it? Chain you to the train?
        anticensor 8y ago
huhtenberg 8y ago
The same goes for airfares. A round-trip can be cheaper depending on direction of travel. One-way trip can be significantly cheaper if you are flying through a major hub like FRA and starting your journey from a less wealthy country.

by sshine 8y ago

deleted 8y ago

[deleted]

gumby 8y ago

Really?? Is that true only when there are multiple paths between A & B or is there something else involved?

CydeWeys 8y ago
Other possibilities: Trains going in different directions don't make the same stops (express vs local), and time-based fares applying to a specific direction based on commuting patterns. In the US, on Amtrak, a ticket is specific to an exact train, like buying a plane ticket. There's no generalized "I want a ticket from DC to NYC."
- bunderbunder 8y ago
  Some of the shorter ones have unreserved coach class tickets that aren't restricted to a specific train. So, while there is no generalized, "I want a ticket from DC to NYC", there is a generalized, "I want a ticket from Chicago to Milwaukee."
bunderbunder 8y ago
Chicago has a minor version of this, even without zone fares: The entry fee to get on a train is $2.50 everywhere except O'Hare Airport, where it's $5.
- gumby 8y ago
  Interesting, thanks!
- notyourwork 8y ago
  The tourist fee.
  - bunderbunder 8y ago
    Nah. Most the people I see on that train are people commuting to/from work, and locals who live along the blue line corridor. Some tourists, but I think most of them are opting to pay a driver 8x as much to take even longer to get them downtown.
tzs 8y ago
Another possibility is that there is more demand in one direction. You might have a major city, A, a center of finance and law and full of corporate headquarters, and a smaller city, B, where many of the companies whose headquarters are in A have their engineering and manufacturing facilities. Someone making a deal with one of those companies may need to visit both engineering to work out technical details first and then visit headquarters to work out business, financial, and legal details. They will travel from home to B, and then travel to A, and then when done travel directly home from A. This may happen much more than the other direction--people needing to visit headquarters first and then going to visit engineering and manufacturing, without needing to go back to headquarters. Net result: more passengers needing B to A than A to B. This can result in A to B trips having empty seats. It might even result in some trips with no passengers at all! They can't simply cancel those trips, because they need to get the vehicles to B to handle the B to A traffic, so they sell seats cheap.
Lewton 8y ago
They use a zone system, and you don’t have to pay for a zone if you get off at the first stop after entering it. This creates the asymmetry
- gumby 8y ago
  thanks
sshine 8y ago
For busses, the B stop on the way out may be in another zone as the B stop on the way back because they're geographically displaced. For busses and trains, depending on your type of ticket (2-8 zones, 8+ zones, commuter card) and whether the zone intersection is on or between stops/stations, you may have to pay for that zone one way but not the other. Those are edge cases. But the most confusing part is the ring topology (here shown with the zone-ring center being the actual city center): https://passagerpulsen.taenk.dk/sites/default/files/styles/full_width/public/zonekort_movia_hjside830x400.jpg https://passagerpulsen.taenk.dk/sites/default/files/styles/f... When buying 2-8 zones you don't pay for individual zones, but rather rings from your origin zone. Going one way, the zone rings look one way. Going back they look different, because the origin zone is different. A practical example of this peculiarity: You go from Hellerup (zone 2) to Friheden (zone 33) via the central station (zone 1). Your ring 0 is zone 2, and zone 1 and 33 are both in ring 1, so you only pay for two zone(-ring)s: https://dinoffentligetransport.dk/media/1413/svanemollen-friheden.jpg https://dinoffentligetransport.dk/media/1413/svanemollen-fri... You go back from Friheden to Hellerup via the central station: Your ring 0 is zone 33, zone 2 is in ring 1, but zone 1 is in ring 2 this time, so you pay for three zone(-ring)s: https://dinoffentligetransport.dk/media/1411/friheden-svanemollen.jpg https://dinoffentligetransport.dk/media/1411/friheden-svanem... Your origin zone on the way out was adjacent to both other zones needed (needing only 1 ring), but your origin zone on the way back was not (needing 2 rings). So they're not just different prices: The graph that spans train stations via zones in the ring topology is not metric. So getting a return ticket is not the inverse of getting the ticket out. And while you have a ticket that's valid for the timespan of your return, it may not be valid for your return path.
- deleted 8y ago
  [deleted]
- ZeikJT 8y ago
  What the... that was painful to read and comprehend. Was this kind of complexity really necessary? Did someone get a promotion for coming up with this?
  - sshine 8y ago

buckminster 8y ago

The rail network in the UK is also strange. On some routes it is cheaper to split your journey across multiple tickets. On others it is cheaper to buy a ticket for a longer journey. However, this is illegal and the train companies do attempt prosecutions.

saganus 8y ago
Why is it illegal and how do they enforce it? I know that something similar happens with airplane tickets but they get you with the luggage and with terms & conditions AFAIK. How is it similar/different with train tickets?
- buckminster 8y ago
  It is illegal because the railway byelaws make it illegal. The railway doesn't just have its own law, it also has its own police force, The British Transport Police, though as far as I know they don't do the ticket enforcement. You are not allowed to break a journey either, so a ticket inspector can spot a ticket for a longer journey at one end of the other. The multiple tickets ruse is more of a grey area.
  - DonaldFisk 8y ago
    BREAK OF JOURNEY Rules vary by train company and route. In general you cannot break your outward journey (except for necessary changes of train) but you can break your return journey. Source: https://www.splityourticket.co.uk/info/fare-types.aspx https://www.splityourticket.co.uk/info/fare-types.aspx I've already dealt with the legality of split ticketing in another post.
    - aaaaaaaaaab 8y ago
      And how do they enforce it? Chain you to the train?
      - anticensor 8y ago

huhtenberg 8y ago

The same goes for airfares. A round-trip can be cheaper depending on direction of travel. One-way trip can be significantly cheaper if you are flying through a major hub like FRA and starting your journey from a less wealthy country.