FARE BASED TRANSIT NETWORKS. Hyper-Network Generation Procedure and Specification

Transcription

1 FARE BASED TRANSIT NETWORKS Hyper-Network Generation Procedure and Specification Peter Kucirek, M.A.Sc. June 6, 2014

2 1 Preface The GTHA system of transit fares largely comprises individual agencies with an initial boarding fare and free transfers intra-agency. It unusually complex and very difficult to model using Emme, which lacks the ability to apply initial fare costs selectively. Prior work has experimented with the idea of using a hyper-network to model fares. The concept is theoretically sound, however its implementation was inflexible and utilized centroid connectors as key elements in its implementation. This feature made it difficult to apply to different zone systems, of which there are several in the region. Additionally, it is very advantageous to be able to not only model the current state of fares in the GTHA, but to also be able to test alternate fare scenarios. Therefore, it is desirable to create a general solution to problem; one that can be used to model both existing and alternate systems and that is not constrained to work with only one zone system. TMG has developed a procedure to generate the base fare-based transit network (FBTN), implemented as a Modeller Tool inside of the TMG Toolbox: Network Editing -> FBTA -> Create from schema 1. The remainder of this document split into four parts. The first part describes the structure of the resulting hyper-network, and how it is generated using a Modeller Tool. The second part details the input fare schema file, and how it is applied by the Tool. The third part provides some additional detail on usage and performance. The last part describes how the 2012 base fare schema was compiled, its sources, assumptions, and behaviours. 2 Hyper Network Generation Procedure The concept of a hyper network is that each agency has its own layer of virtual links and nodes, which are only connected to the base network by auxiliary transit (walk) links that contain the transit fare cost 2. In this implementation, this has been generalized to have each transit line belong to a group (instead of a hard-coded operator), in order to give the procedure more flexibility. The groups are specified using a fare schema file (see next section for details). The main assumption of this approach is that transfers between lines within the same group are free (unless a boarding cost is applied during assignment). To generate the appropriate hyper-network, six steps are followed: 1. Transit lines are classified into groups based on the fare schema file. 2. The network is pre-processed. The procedure attaches to each node a two sets of data: groups which are stopping at the node, and groups which are passing through the node. The two sets are mutually exclusive. Two groups of (non-zone) nodes are identified: 1 Also implemented as an XTMF module: GTAModel.NetworkAssignment.BuildFbtnFromSchema 2 Historical footnote: in prior implementations, these virtual links were only created when two operators shared links. Fare costs were applied to centroid connectors only. Page 1 of 15

3 a. Road (or Surface) nodes are connected to at least one link with the auto mode. b. Transit (or Station) nodes are connected to links with only transit or walk modes. 3. Surface nodes are processed first. For each group using a surface node (either stopping at or passing through), a new virtual node is created. The base node s attributes are copied over. For groups stopping at the node, the associated virtual node is connected using walk links to the base node and to each other. These walk links are indexed for later use The same procedure is followed for station nodes, except that virtual nodes are only created when two or more groups use the station node 4. This is done as station nodes already exist in their own layer in the network (e.g. subway links and nodes), and therefore do not need to moved over to a new layer. Any existing connected walk links are indexed appropriately. 5. Virtual surface nodes and virtual station nodes are connected to each other using walk links. 6. Finally, each transit line is moved over to its appropriate layer in the hyper network. In-vehicle links are created between virtual nodes when none exist. It should be noted that, currently, no effort is made to make the network look visually appealing. Virtual nodes are given the exact same coordinates as their base node, and virtual links copy the same shape as their base links. Therefore, the created hyper-network appears to be identical to the base network since the virtual nodes and links overlap the base precisely. 3 Fare Schema File Specification The new TMG implementation uses a fare schema file, implemented in Extensible Markup Language (XML). XML is a widely-used, hierarchical format which is human-readable. The fare schema file specification prescribes 3 collections of items necessary for generating the hyper-network : <groups>, <zones>, and <fare_rules>. 3.1 Groups Contains a list of transit line groupings. Conceptually, these groupings can be distinct transit agencies (e.g., TTC, GO Transit), but could also be distinct sub-groups of one agency (e.g. TTC Regular vs. TTC Downtown Express). It is important that ALL transit lines belong to a group to ensure proper behaviour when modelling transit. Also important to note is that each group will become its own layer in the hyper network generation procedure. Fewer groups reduces the size of the hyper network which, in trials, have surpassed maximum size allowed by the standard Emme license. Each group element contains a set of transit line selector expressions (used by Emme s Network Calculator) to select its lines. Groups are processed IN ORDER, so if a line meets the criteria for multiple groups, it will be assigned to the LAST group in the schema file. Each group must have a unique ID. <group id="ttc Regular"> <selection>line=t </selection> 3 A matrix data structure (NOT an actual Emme Matrix) stores sets of links, where each row and each column correspond with a transit line group. The 0 th index of the matrix refers to the base network. 4 In practise, this is very rare; with less than 5 occurrences in the TMG base network. Page 2 of 15

4 <group id="ttc DT Express"> <selection>line=t14 </selection> 3.2 Zones An optional element containing a list of fare zones and a list of shapefiles. Each node in the network can be assigned to a single zone. If a node meets the requirements for multiple zones it will be assigned to the LAST zone in the schema file (similar to groups). Each zone must have a unique ID. Two different types of fare zones are supported: node_selection and from_shapefile. Node selection zones apply a set of node selector expressions (used by Emme s Network Calculator). Zones loaded from shapefile reference an FID (feature ID) in one of the included shapefile elements. <shapefile id="1" path="d:/workspace/08 GTAModel V4/Data/Fares/York_Region_Zones.shp" /> <zone id="toronto" type="node_selection"> <node_selector>i=10000,20000</node_selector> </zone> <zone id="york 1" type="from_shapefile"> <from_shapefile id="1" FID="1" /> </zone> 3.3 Fare Rules Contains a list of fare rules to be applied to the hyper network once it has been generated. Each fare rule element has an associated cost and type, and sub-elements to determine which links or segments it applied to. During processing, fare rules are applied in order; with each fare rule s cost being added to its selected links or transit segments. This is an important distinction, as it allows fare rule costs to be negative, so long as the resulting summed value is greater than zero. For example, Hamilton Street Railway (HSR) has an initial fare of $1.65 5, with a special co-fare of $0.50 to GO Transit, which discounts the initial fare when riders transfer to GO train stations using HSR. To model this, two fare rules are required: A fare of $1.65 applied to all links incoming to HSR s layer of the transit network. A negative fare of $1.15 applied to links transferring from HSR to GO and from GO to HSR. 5 Average adult fares, taking into account passes, tickets, and other discounts. Page 3 of 15

5 So, when egressing from GO to HSR, the on-link fare is $ $1.15 = $0.50, which is the appropriate cofare. In the other direction, the discount is actually applied to the access-link to GO Transit, which uses an initial fare of $3.55. This works out to be $ $1.15 = $2.40; which is the resulting discount for transferring to GO. There are four fare rule types: initial boarding, transfer, zone crossing, and distance in vehicle Initial Boarding Rule (group, [in_zone]) Initial boarding rules have their cost applied to all LINKS inbound to the layer of the specified group. This rule can be further restricted to applying only to links starting from a specified ZONE. <fare cost="1.98" type="initial_boarding"> <group>ttc Regular <fare cost="0.15" type="initial_boarding"> <group>ttc Regular <in_zone>york 1</in_zone> Transfer (from_group, to_group, [bidirectional= False]) Transfer rules have their cost applied to all LINKS connecting one group s layer to another s. By default, this rule is applied one-way (to links from to to ) but can also be set to bidirectional (also applied to links to to from ). <fare cost="-2.23" type="transfer"> <from_group>hsr</from_group> <to_group>burlington Transit</to_group> <fare cost="-1.28" type="transfer"> <from_group>miway</from_group> Zone Crossing Rule (group, from_zone, to_zone, [bidirectional= False]) Zone crossing rules have their cost applied to all SEGMENTS whose i-node belong to the specified fromzone and whose j-node belong to the specified to-zone, for the specified group. Like transfer rules, they too can be applied in a bidirectional fashion. Page 4 of 15

6 <fare cost="2.13" type="zone_crossing"> <group>ttc Regular <from_zone>toronto</from_zone> <to_zone>york 1</to_zone> <fare cost="1.00" type="zone_crossing"> <group>yrt <from_zone>york 1</from_zone> <to_zone>york 2</to_zone> Distance In-Vehicle Rule (group) Distance in-vehicle rules have their cost applied to all SEGMENTS belonging to their specified group. This cost is multiplied by the segment LENGTH attribute (inherited from the segment s link) in other words, the cost attribute is specified in $ per km. <fare cost="0.0825" type="distance_in_vehicle"> <group>go Transit 4 Usage and Performance This section will cover how to use the above specification to generate new fare scenarios, as well as how to use the FBTN to run transit assignments. 4.1 Constructing New Fare Scenarios The fare rule types specified in the Fare Schema File (FSF) can be combined to generate flexible fare scenarios to test. Fare costs are applied to two types of network elements Links and Transit Segments saved into user-specified Extra Attributes. Rules in the FSF are applied sequentially and additively; if a link or transit segment meets the criteria for multiple rules, the resulting value will be the sum of the costs. See Section 3.3 for an example of how these rules can be set up. Internally, the tool indexes Links and Segments while creating the FBTN. Links are indexed into a table whose rows and columns correspond to the group number (where 0 represents the base network). For example, if the TTC is group 1, then the grid at [0, 1] contain all of the links from the base network to the TTC virtual layer. A similar table indexes Segments based on which zones they cross. This framework leaves room for future extensibility, should new fare rule types be required. Page 5 of 15

7 4.2 Limitations There are limits to the types of fare rules that can be expressed using the above framework. Rules that are time-dynamic, that require information about the time that has elapsed since the beginning of a path, are not possible to model within Emme s time-static framework. Rules which apply to different classes of passenger (e.g. student and/or senior fares) are not supported by this framework, although it might be possible to model using multiple Emme assignments. Finally, rules which require origin-to-destination information, or access-point-to-egress-point (e.g. GO transit fare zones) are not possible to model without access to the path-building algorithm, which Emme does not provide. However the last rules can be approximated using either in-vehicle distance or using zone-crossing rules. 4.3 Transit Assignment The generated FBTN is compatible with Emme Transit Assignment tools (Standard, Extended, Congested, etc.), although the Standard Transit Assignment cannot be used to run fare-based transit assignment (FBTA). It is easy enough to configure the Extended Transit Assignment tool (and the others) to run an FBTA: Use the Link Extra Attribute containing transfer fares and an Auxiliary transit cost (with the appropriate perception factor), and use the Transit Segment Extra Attribute containing in-vehicle fares as an In-vehicle cost (with the appropriate perception factor). See Figure 1 below for an example. Figure 1: Setting up FBTA using Extended Transit Assignment 4.4 Performance There are no significant performance issues when using this tool. The FBTN generation procedure took approximately 30 seconds to run on the TMG machines. A non-fbta was run on the resulting network and there were no noticeable lags in the performance. Page 6 of 15

8 An important detail to note: while developing this tool, TMG staff ran into issues with network size. The procedure required more nodes than a Size 13 license permitted. To address this issue, another tool was developed to reduce the node requirements by deleting mid-block nodes while preserving link attributes. Over 3,000 nodes were removed from the 2012 Base Network, which was sufficient to successfully run the FBTN generation procedure. A separate tool to estimate the required network size has also been developed Base Fare Schema In creating the base fare schema file, 2012 fare prices were obtained from every GTHA transit agency. However, these data are what each agency shows to the public and do not reflect what is actually paid per-ride. A different value must be calculated, which blends the effects of different fare media: cash, tokens, and monthly passes. Fortunately, the TTC was able to provide a figure for average adult fare, which was used to pro-rate the unit price for 10 tickets for other agencies. This data is summarized in Table 1 below. The full base schema is transcribed in Appendix A. 5.1 Co-fares and Transfers With the exception of the TTC, all agencies offer a lower co-fare when transferring to and from GO Transit. These have been implemented as negative-cost fare rules, where the initial boarding fare is subtracted from the co-fare to get the difference applied to the appropriate transfer links. These co-fares are documented in Table 1. Additionally, several non-toronto agencies accept free transfers from each other (for example, Hamilton and Burlington). However, these are usually restricted by time of trip (e.g. within a two-hour period from the original time of purchase). This is just not possible to model within a time-static framework, and so these free transfers were omitted from the base schema. Agency Ticket price Average adult fare Applied initial boarding fare GO Transit Co-fare Applied Co-fare Toronto Transit Commission $ 2.60 $1.98 $1.98 #N/A #N/A (TTC) Durham Region Transit (DRT) $2.70 #N/A $2.05 $0.75 -$1.30 York Region Transit (YRT) $2.80 #N/A $2.13 $0.75 -$1.38 Mississauga Transit (MiWay) $2.60 #N/A $1.98 $0.70 -$1.28 Brampton Transit $2.75 #N/A $2.09 $0.65 -$1.44 Oakville Transit $2.65 $2.27 $2.27 $0.65 -$1.62 Milton Transit $2.40 #N/A $1.82 $0.70 -$1.12 Burlington Transit $2.50 $2.23 $2.23 $0.65 -$1.58 Hamilton Street Railway (HSR) #N/A $1.65 $1.65 $0.50 -$1.15 Table 1: Initial Fares and GO Co-fares Page 7 of 15

9 5.2 TTC Downtown Express, TTC Routes in York Region The TTC operates a handful of premium routes as Downtown Express routes: 141, 142, 143, 144, and 145. In addition to the normal TTC initial boarding fare, an additional fare of $2.70 is required (if transferring from the TTC). Boardings from other agencies or first boardings are required the initial TTC fare plus the surcharge, which works out to be $4.68. A negative cost rule is applied when transferring from TTC to DT Express (and vice-versa) routes to account for having paid the TTC fare already. Additionally, the TTC operates a number of routes north of Steeles Avenue, which is the official N/S boundary between Toronto and York Region. Passengers on-board pay an additional surcharge to cross in to or out from York Region. Within York Region, passengers pay YRT price for the initial boarding (the difference between YRT and TTC is $0.15), and must pay the surcharge when crossing Steeles. 5.3 YRT Fare Zones YRT divides York Region into three fare zones (1, 2, and 3). The boundaries between the fare zones are fairly wide (containing several stops), where the $1.00 surcharge is applied only if a passenger s trip starts on one side of the fare boundary and ends on the other side. This soft boundary is not possible to model using Emme, since it involves knowing both end of the trip in advance (see GO Transit below), and so it is approximated using a hard zone crossing halfway through the soft boundary. Figure 2 below illustrates the location of each of the YRT fare zone boundaries. The boundary between Zone 1 and Zone 2 follows King Road, while the boundary between Zone 2 and Zone 3 follows Ravenshore Road. Page 8 of 15

10 Figure 2: York Region Fare Zones Page 9 of 15

11 Average Adult Fare Between Zones Fare Based Transit Networks 5.4 GO Transit GO Transit fares work on a zone system, where the cost of a ticket depends on which station one boards at and which station one alights at the cost paid per ticket was provided as an origin-destination matrix. This is difficult to model from the route-choice perspective given the constructive nature of path-building. Therefore GO fares are approximated as a per-km fare, with an initial boarding fare. The initial fare comes directly from the fare matrix and is the minimum cost of a GO trip and also the cost of travelling within a single zone. The per-km fare was estimated using linear regression, based on the network distance between fare zones; where the network distance is the minimum shortest path distance between GO stations/stops in each zone. If between two zones there existed a path using just railway links, that path s distance was used. Figure 3 shows the results of the linear regression. The actual fares used in the estimation were blended across different fare media, since the given fares were for cash-only (the highest price). Data from Metrolinx indicated that 60% of GO riders paid using a PRESTO card, realizing a 17.5% discount on the ticket price. It was assumed that the remaining 40% of riders paid by cash. With this blending, the final applied initial boarding fare was $4.07, and the final perkm fare was $ (8.28 cents). $30.00 $25.00 $20.00 y = x R² = $15.00 $10.00 $5.00 $ Minimum Distance (km) Between Zones Figure 3: Linear Regression on GO Fares vs. Distance Page 10 of 15

12 Appendix A: Transcribed 2012 Fare Schema File <?xml version="1.0" encoding="utf-8"?> <root> <version number="1.0" /> <groups> <group id="ttc Regular"> <selection>line=t </selection> <group id="ttc DT Express"> <selection>line=t14 </selection> <group id="go Transit"> <selection>mode=rg</selection> <group id="drt"> <selection>line=d </selection> <group id="yrt"> <selection>line=y </selection> <group id="miway"> <selection>line=m </selection> <group id="brampton Transit"> <selection>line=b </selection> <group id="oakville Transit"> <selection>line=ho </selection> <group id="burlington Transit"> <selection>line=hb </selection> <group id="milton Transit"> <selection>line=hm </selection> <group id="hsr"> <selection>line=w </selection> </groups> <zones> <shapefile id="1" path="d:/...yorkzones.shp /> Page 11 of 15

13 <zone id="toronto" type="node_selection"> <node_selector>i=10000,20000</node_selector> </zone> <zone id="york 1" type="from_shapefile"> <from_shapefile id="1" FID="1" /> </zone> <zone id="york 2" type="from_shapefile"> <from_shapefile id="1" FID="0" /> </zone> <zone id="york 3" type="from_shapefile"> <from_shapefile id="1" FID="2" /> </zone> </zones> <fare_rules> <!--TTC (Toronto Transit Commission)--> <fare cost="1.98" type="initial_boarding"> <group>ttc Regular <fare cost="4.68" type="initial_boarding"> <group>ttc DT Express <fare cost="-1.98" type="transfer"> <from_group>ttc Regular</from_group> <to_group>ttc DT Express</to_group> <fare cost="0.15" type="initial_boarding"> <group>ttc Regular <in_zone>york 1</in_zone> <fare cost="2.13" type="zone_crossing"> <group>ttc Regular <from_zone>toronto</from_zone> <to_zone>york 1</to_zone> <fare cost="1.98" type="zone_crossing"> <group>ttc Regular <from_zone>york 1</from_zone> <to_zone>toronto</to_zone> <!-- GO Transit Fares --> <fare cost="4.07" type="initial_boarding"> Page 12 of 15

14 <group>go Transit <fare cost="0.0825" type="distance_in_vehicle"> <group>go Transit <!-- Durham Transit --> <fare cost="2.06" type="initial_boarding"> <group>drt <fare cost="-1.41" type="transfer"> <from_group>drt</from_group> <!-- York Region --> <fare cost="2.13" type="initial_boarding"> <group>yrt <fare cost="-1.38" type="transfer"> <from_group>yrt</from_group> <fare cost="1.00" type="zone_crossing"> <group>yrt <from_zone>york 1</from_zone> <to_zone>york 2</to_zone> <fare cost="1.00" type="zone_crossing"> <group>yrt <from_zone>york 2</from_zone> <to_zone>york 3</to_zone> <!-- MiWay --> <fare cost="1.98" type="initial_boarding"> <group>miway <fare cost="-1.28" type="transfer"> <from_group>miway</from_group> Page 13 of 15

15 <!-- Brampton Transit --> <fare cost="2.09" type="initial_boarding"> <group>brampton Transit <fare cost="-1.44" type="transfer"> <from_group>brampton Transit</from_group> <!-- Oakville Transit --> <fare cost="2.27" type="initial_boarding"> <group>oakville Transit <fare cost="-1.62" type="transfer"> <from_group>oakville Transit</from_group> <!-- Burlington Transit --> <fare cost="2.23" type="initial_boarding"> <group>burlington Transit <fare cost="-1.58" type="transfer"> <from_group>burlington Transit</from_group> <fare cost="-2.23" type="transfer"> <from_group>hsr</from_group> <to_group>burlington Transit</to_group> <!-- Milton Transit --> <fare cost="1.83" type="initial_boarding"> <group>milton Transit <fare cost="-1.23" type="transfer"> <from_group>milton Transit</from_group> Page 14 of 15

16 <!-- HSR --> <fare cost="1.65" type="initial_boarding"> <group>hsr <fare cost="-1.15" type="transfer"> <from_group>hsr</from_group> </fare_rules> </root> Page 15 of 15