computing line-to-line transfer matrices with emme/2
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1. t t 15 5 29 liz iT 14 255 3 z z a t 5 20 254 z 5 245 z z z a t 5 19 2t z z 5 Tazi B z z s 1 t 1 28 2rec 5 z z iT 12x z t2 z z z B ti z t t5 z 2 z z 1 T z z E Te T z z a 16 The z z z 3 14 thet 3 z z z z 15 52 a T T b B a tE Th a b b 5 5 3 t 12 40 hier 10 z z a t t t oO hie 5 z z iT Accent zb 2b 25 z 25 2 22 t z z 3 5 zb 23 22 t 222. In the following sections we will describe a new methodology designed to overcome the problems mentioned above The approach allows to compute such line to line transfer matrices for selected nodes with the standard EMME 2 software release as a by product of a single standard transit assignment This is done by a special network transformation at the transfer node which does not alter the mathematical formulation of the transit assignment problem i e yields the same results as before the transformation but which renders the line to line transfers accessible as boardings and alightings of special transfer segments Network Representation at Transfer Node In a standard network a transfer node is connected by incoming and outgoing links Each link can carry an arbitrary number of transit line segments and allow a subset of auxiliary modes for accessing to or egressing from the transit lines For the sake of simplifying the presentation we assume that all lines actually stop at the transfer node and allow both boarding and alighting This is illustrated in Figure below n ry i E i m L a ul xj L 7 7 B S la E Ds 1 7 EUM z i vnum ss Tem I 1205 A O E Le et E Tee S O4 oe O Ra er pora 1 E i T ae _ ye im ZU VE ae laden Sati oa EL D i T 1 r 6 u Ju on B i rr E NUM En J noa EN 1 2 al Figure 1 Simple transfer node The key idea of our method is to blow up the tr
3. are all incoming and outgoing auxiliary mode links All lines allow only boarding but no alighting at this node Thus M r4 will be used by all trips accessing the transit system at node T as well as by all trips passing T on auxiliary mode links Figure 2 below illustrates the transformation of the transfer node T A s V a Fa i LI i m A El Erp E LI uq T E E a _ UI Sh a o H c e ires wl oU A amp V nok Vu Hh vU BGs d i Es i BS H 38 8 5 8 H 8 1 3 1 8 4 a ial i M ARA 8 5 85 eee o Rs i T E NET 2 Mr 4 1 IX ae m I C ART 0T m r ul g n 5 E i D LIGHT a z EDAED 3 M Figure 2 Extended transfer node structure Note that the blown up transfer node allows for exactly the same set of route choice strategies with exactly the same costs associated to each But depending on the behavior of a strategy at the transfer node egress transfer from line access and auxiliary mode passage the strategy is forced to use one particular node My Automatic Network Transformation While the proposed topological transformation of the transfer node 1s quite simple in principle it is still not a trivial task to actually carry out the corresponding network modifications in EMME 2 Of course it is possible to do it interactively but the task is cumbersome repetitive and prone to errors Hence it is really desira
4. 1 total 112 55 55 28 12 2b 14 of 5 zr ot 52 20 5 T 25 tz 5 bat Conclusions We have shown that the computation of consistent line to line transfer matrices is theoretically possible and also practically feasible with the standard EMME 2 software release The macro we developed for this purpose has been written to be as independent of the specific application as possible In specific contexts however it is possible to adapt the same ideas to particular project requirement Instead of computing transfer matrices on the level of individual transit segments it would e g be possible to compute aggregate transfer matrices by line link or mode groups Of course the more aggregate the resulting transfer matrices are the smaller the required amount of computing resources The basic idea of adding this kind of additional structure at transfer points can also be exploited for other purposes than just the computation of detailed transfer information Since the various types of transfers can now be channeled to different nodes these can also be defined to have different characteristics such as node dependent boarding times and wait factors This could be very useful to build more detailed assignment models by taking into account transfer specific fare rules node specific boarding times and timed transfers node specific wait factors References Aho Kernighan and Weinberger 1988 The AWK Programming Language Addison Wesley Publishi
5. COMPUTING LINE TO LINE TRANSFER MATRICES WITH EMME 2 Heinz Spiess EMME 2 Support Center CH 2558 Aegerten Switzerland March 1992 Abstract When assigning a transit network with EMME 2 the basic results are the volumes on the transit segments and the boardings alightings at the transit stops Means to produce line to line transfer matrices at transfer nodes are not provided as a standard result output In this paper we show how such line to line transfer matrices can be computed for selected transfer nodes without changing the assignment results This is done with the standard EMME 2 software by using a special network transformation at the selected transfer nodes Details of this transformation are discussed and we show how the process has been automated by implementing it as a macro The method is illustrated with an example from the Winnipeg standard demonstration data bank In the conclusions we discuss how this methodology can be extended to model other complex situations which are not covered by the standard model This paper was presented at the Ist European EMME 2 Users Conference London April 1992 Introduction When modelling transit networks the basic results provided by the transit assignment in the EMME 2 software package are the volumes on the transit line segments as well as the boardings and alightings at each transit stop Of course other information is also computed during the transit assignment such as the numbe
6. E TO LCHE TERHHFER PATAI AT HOLE 429 POULE 8 B E H 3PIEZE He Figure 4 Transfer structure at node 423 Next the standard assignment was run again on the modified network and the resulting transit segment volumes were compared with the original ones in order to verify that the route choice had not changed Note that very small changes can occur in the volumes they are due to different rounding in the assignment process and different handling of ex aequo situations In this case the volumes were identical for all practical purposes the largest volume difference being only about trip Finally the macro transfer was run again this time using the functionality to generate a report of the transfer matrix at nodes 423 and 454 The report obtained for node 423 is shown below The column egress denotes trips which alight at node 423 and leave it through an auxiliary transit link The row access denotes trips that get to node 423 through an auxiliary transit link and then embark on a transit line The other rows and columns are labels with the corresponding transit line name and a direction indicator gt or CIQE TO CIIE TLLIISPFELS LT IODE 25 fromy io osgress J S Oc 115 11 235 232 2 5 SEC Aeb 2Tec Tae f2 Ths Tit Ths Tie Theat bel Ths Tht peb poeg total 10 gt t t 15 5 2 20 1i
7. ansfer node by adding dummy nodes links and segments in such a way that e The mathematical structure of the transit assignment is not altered This means that no time or cost element is added and that the new topology still allows exactly the same set of strategies e The elements of the line to line transfer matrix appear as boardings or alightings at the dummy nodes This goal is possible to achieve by using the following transformation Let s assume that we have L lines numbered to L passing at a transfer node N In this case the node N is transformed into a linear sequence of L 2 nodes connected with links of zero length i e Wo 4 Ma Ir Ii ra All transit lines passing through T are newly routed through these nodes with zero time segments No is the egress node All incoming line segments are connected to this node as well as are all outgoing auxiliary mode links All lines allow only alighting but no boarding at this node Thus o will be used only by trips egressing at node 7 Ny IV p are the line specific transfer nodes At node Ng alighting is allowed only for line For all other lines only boarding is allowed at Ne Thus iN will be used exclusively by trips transferring from line to other lines Since there are no auxiliary modes connected to Ny no access and egress movements are possible A r 1is the access node All outgoing line segments are connected to this node as well as
8. ble to automate this procedure Since the topological transformation to be performed is based on a small set of simple and strict rules it is possible to implement the entire procedure as an EMME 2 macro In the following we describe a prototype implementation of such a macro It is called transfer and is based on the Beta Release 5 EMME 2 version of EMME 2 a pre release version containing some of the new features which will be part of Release 6 In particular the new possibilities of editing networks using batch input proved very useful when developing the macro The macro blows up a given transfer node by modifying the node link and transit line table of the current scenario If the line to line transfers are needed for several transfer nodes the macro can simply be applied repetitively Here a brief description of the steps performed in the macro 1 The transfer node itself as well as all incoming and outgoing base network links are punched using module 2 14 2 A file containing all line segments ending at the selected transfer node is generated using the network calculator in module 2 41 All transit lines are punched using module 2 24 The transit line table is initialized using module 2 22 5 Using a command escape the AWK script transfer awk which constitutes an integral part of the macros is activated It parses the files generated in steps 1 and 2 and generates a base network modification file 6 This base network modi
9. es some conditions on the network used e The transit time functions used on the incoming segments of the transfer node should not depend on the auto times This is due to the fact that the lines now enter the transfer node no longer through the direct link on which the auto mode is defined but through the dummy node Ip If the transit times on these segments do depend on the auto times those times should be copied to a user data item before a transit assignment and the transit time functions should be adjusted accordingly e Ihe volume delay functions used on the incoming auto link of the transfer node should not depend on the volume of the transit vehicles This is due to the fact that the lines now enter the transfer node no longer through the direct link on which the auto mode is defined but through the dummy node No If the volume delay functions on these links do depend on the transit vehicles those transit vehicle volumes should be copied to a user data item before a auto assignment and the volume delay functions should be adjusted accordingly e All lines passing through the transfer node allow alighting at that node If this 1s not the case the alighting flags at the egress node have to be adjusted manually after the macro has terminated Once the transit assignment has been performed the line to line transfers are available as boardings and alightings at the dummy nodes Since in this form they are not easily accessible a seco
10. fication file is processed using module 2 11 7 Using a command escape the AWK script transfer awk is again activated This time it removes the path no clauses from the transit line file generated in step 3 so that the line itineraries will now automatically be routed men through the new node sequence No N L 1 8 The transit line file resulting from the previous step is read into the data bank using module 2 21 9 The attributes of the newly added transit segments connecting nodes Ng Nr Li are set to the proper values using the network calculator module 2 41 Note that since the macro will increase the network size it is up to the user to make sure that enough space is still available in the scenario to hold the new network elements Assuming that at node 7 there are L incoming line segments and A adjacent links incoming or outgoing then the network transformation will require at most L additional nodes A L additional links and L L additional line segments Once the macro has terminated the scenario a transit assignment can be performed normally and all the display and analysis tools can be used as usual Since all dummy nodes that are used for exploding a transfer node are located on top of the original transfer node it suffices to select only those links that are outgoing from real network node in order to obtain the same network plots as before transformation Note that the current implementation of the macro impos
11. in the application In the past two types of simplistic approaches to solve this problem have been used in practice by some EMME 2 users In the first type of methods the network topology is changed by splitting the transfer node into different nodes which are interconnected with a matrix of walk links The big drawback of this approach is that this network transformation changes the route choice and thus the assignment results since the lines at the transfer node can no longer be combined to reduce waiting time In the second type of approach the network 1s left unchanged but instead of a simple assignment a series of assignments is carried out mimicing a transit version of an additional options auto assignment In the first step of this process a partial demand matrix representing the trip using a given line or set of parallel lines is extracted In the second step this matrix is assigned again to the transit network The resulting boardings to and alightings from the other lines passing at the transfer node can then be interpreted as the line to line transfers between the selected line and the other lines calling at the transfer node While this method does not change the route choice of the trips it is very time consuming several assignments needed it gives only partial information relative to one line and it 1s only applicable if the line or set of lines in question are not used combined with other lines at the transfer node
12. nd functionality has been embedded in the same macro transfer Itis used to collect the informations from the dummy segments and to transform them into a nicely formatted report of the line to line transfer matrix This report is annotated with the transit line names and the directions gt or An example of the report is given in the next section An Example The following example output was generated using the standard EMME 2 Winnipeg demonstration data bank Since in the Winnipeg network the transit times depend on the auto times those were copied into a link user data item and the transit time functions were modified accordingly Then the macro transfer was run twice in a row adding the line to line transfer structures to the nodes 423 and 454 Figure 3 shows the details of the line itinerary around node 423 before running the macro HIHAT d14 1 547 Tu JEg 1 T EHHE E PAQZECT EXME E STANDARD DEPHRHSTPHTIUOH ABD TEST CATA BEEF BCEMAARCO xx HIBMHIPEL 16H ALAD AHO TFPHBHIT PETHOR Figure 3 Line itineraries at transfer node 423 Figure 4 shows the transfer structure at node 445 generated with the macro In order to graphically display the structure the macro was called with the option to stagger the dummy nodes instead of hiding them behind the transfer node TRANSIT AND BUXILIBRY TRANSIT VOLUMES ES e EHHE E PALET BEHEE HIHURRD DEHDHETHHTIDH FE TEST DHTR BRAF DATE ud r HEEMRRIDU SS GORPUTE LIM
13. ng Company INRO Consultants Inc 1991 EMME 2 User s Manual Release 5 0 INRO Consultants Inc 1992 EMME 2 Release Notes Beta Release 54 Spiess and Florian 1989 Optimal Strategies A New Assignment Model for Transit Networks Transportation Research B Vol 32B No 2 pp83 102 Back to EMME 2 Support Center Homepage Heinz Spiess EMME 2 Support Center Wed Mar 13 11 29 35 MET 1996
14. r of initial boardings and final alightings at nodes the auxiliary link volumes e g pedestrian movements and the various OD time component matrices These standard results cover the need of the great majority of transit planning applications However in certain applications it is not sufficient to know the total number of transfers at each transfer node but it is necessary to assess the number of trips that transfer at a given node from one particular line and direction to another This means that instead of just the total number of transfers at a given node a line to line transfer matrix is needed Ideally such a transfer matrix could be computed for each transit node in the network But this would amount to a huge quantity of data in general requiring orders of magnitude more storage space than is needed for the standard assignment results For the Winnipeg standard demonstration network there are 57 333 possible line to line transfers but only 4 272 transit line segments Given this and the fact that the number of possible line to line transfers at a node 1s the square of the number of lines stopping at the node which by the way is not restricted in EMME 2 it 1s clear that these transfer matrices are not provided as a standard result in EMME 2 However in practice it is most always necessary to know the transfer matrices at only a few transfer nodes in the network which ones of course depend on the particular issues that are to be studied
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