/sbb-journey-planner

Primary LanguageJupyter Notebook

Final Assignment: Robust Journey Planning

Executive summary: build a robust SBB journey planner for the Zürich area, and make a short video presentation of it, to be done in groups of 5 or 6.

  • Video presentations are due before May 29th, 23:59
  • Code due before May 30, 23:59.

Content

HOW-TO

This section intentionally blank. Students must complete it with instructions on how to use the code in their project.

  1. Set up git lfs
    • git lfs install (essential per repo and per machine)
    • git lfs fetch --all (get all data from lfs essential for project)
  2. Set up Hive's HDFS accesss
    • run "kinit gaspar-account" in terminal (or refresh your ticket by "kinit -R")
    • enter password (although UI does not show any letters)
    • verify you got ticket by running "klist -a" in terminal
    • run prepare-env.md
  3. Run import.ipynb

Important Dates

The assignment (clear, well-annotated notebook and/or code; report-like), with a short, 7-minute video of your presentation is due before May 29th, 23:59 CEST.

For the oral defense, we will organize short Q&A discussions of 8 minutes per group. These discussions will be scheduled on the week of June 5th - actual day and times to be discussed on a case by case basis.

Problem Motivation

Imagine you are a regular user of the public transport system, and you are checking the operator's schedule to meet your friends for a class reunion. The choices are:

  1. You could leave in 10mins, and arrive with enough time to spare for gossips before the reunion starts.

  2. You could leave now on a different route and arrive just in time for the reunion.

Undoubtedly, if this is the only information available, most of us will opt for option 1.

If we now tell you that option 1 carries a fifty percent chance of missing a connection and be late for the reunion. Whereas, option 2 is almost guaranteed to take you there on time. Would you still consider option 1?

Probably not. However, most public transport applications will insist on the first option. This is because they are programmed to plan routes that offer the shortest travel times, without considering the risk factors.

Problem Description

In this final project you will build your own robust public transport route planner to improve on that. You will reuse the SBB dataset (See next section: Dataset Description).

Given a desired arrival time, your route planner will compute the fastest route between departure and arrival stops within a provided confidence tolerance expressed as interquartiles. For instance, "what route from A to B is the fastest at least Q% of the time if I want to arrive at B before instant T". Note that confidence is a measure of a route being feasible within the travel time computed by the algorithm.

The output of the algorithm is a list of routes between A and B and their confidence levels. The routes must be sorted from latest (fastest) to earliest (longest) departure time at A, they must all arrive at B before T with a confidence level greater than or equal to Q. Ideally, it should be possible to visualize the routes on a map with straight lines connecting all the stops traversed by the route.

In order to answer this question you will need to:

  • Model the public transport infrastructure for your route planning algorithm using the data provided to you.
  • Build a predictive model using the historical arrival/departure time data, and optionally other sources of data.
  • Implement a robust route planning algorithm using this predictive model.
  • Test and validate your results. Note that we will put a particular emphasis on the scientific validation of your method.
  • Implement a simple Jupyter-based visualization to demonstrate your method, using Jupyter widgets such as ipywidgets.

Solving this problem accurately can be difficult. You are allowed a few simplifying assumptions:

  • We only consider journeys at reasonable hours of the day, and on a typical business day, and assuming a recent schedule.
  • We allow short (total max 500m "As the Crows Flies") walking distances for transfers between two stops, and assume a walking speed of 50m/1min on a straight line, regardless of obstacles, human-built or natural, such as building, highways, rivers, or lakes.
  • We only consider journeys that start and end on known station coordinates (train station, bus stops, etc.), never from a random location. However, walking from the departure stop to a nearby stop is allowed.
  • We only consider departure and arrival stops in a 15km radius of Zürich's train station, Zürich HB (8503000), (lat, lon) = (47.378177, 8.540192).
  • We only consider stops in the 15km radius that are reachable from Zürich HB. If needed stops may be reached via transfers through other stops outside the 15km area.
  • There is no penalty for assuming that delays or travel times on the public transport network of two different lines are uncorrelated with one another, however try to capture dependenes of stops on the same route, e.g. if a train is late at a stop, it is expected to be late at subsequent stops.
  • Once a route is computed, a traveller is expected to follow the planned routes to the end, or until it fails (i.e. miss a connection). You do not need to address the case where travellers are able to defer their decisions and adapt their journey "en route", as more information becomes available. This would require us to consider all alternative routes (contingency plans) in the computation of the uncertainty levels, which is more difficult to implement.
  • The planner will not need to mitigate the traveller's inconvenience if a plan fails. Two routes with identical travel times under the uncertainty tolerance are equivalent, even if the outcome of failing one route is much worse for the traveller than failing the other route, such as being stranded overnight on one route and not the other.
  • All other things being equal, we will prefer routes with the minimum walking distance, and then minimum number of transfers.
  • You do not need to optimize the computation time of your method, as long as the run-time is reasonable.
  • When computing a path you may pick the timetable of the most recent week and assume that it is unchanged.

Upon request, and with clear instructions from you, we can help prepare the data in a form that is easier for you to process (within the limits of our ability, and time availability). In which case the data will be accessible to all.

Project Submission Checklist

  • Project and 7 minute (max) video are due before May 29th, 23:59.

  • The final assignment is to be done in groups of 5 or 6, remember to update your group member list if needed.

  • All projects must be submitted on Renku, as a group project.

  • Project must contain final in the name, or you can fork this final-project project.

  • Provide instructions on how to test your project in the HOW TO section of the README.md file. Include a link to your video presentation.

  • Project sizes, including history, must not exceed 100Mb. Use git-lfs for your larger data sets, or keep as much data as possible on HDFS.

Note: use git lfs migrate import --fixup --include-ref=refs/heads/master if you accidentally push a large data set on gitlab. See using git lfs responsibly in the renku documentation. Since you will be rewriting history, you will need to unprotect your branch in gitlab and force git push -f, and coordinate with your peers to make sure that you are all working off the same history.

Video Presentations

Instruction for video presentations, due before May 29th, 23:59:

  1. Use Zoom (or other tools) to record your group video.

  2. Save the video as an mp4 file.

  3. Upload your video to moodle under Final assignment - video presentation.

  4. Include the link to the video in the HOW TO section, at the top of the README.md file of your final assignment

Please, DO NOT load the video as part of your project, send a video embedded in a PowerPoint presentations, or use any format other than mp4 videos. We must be able to stream the videos in our web browsers.

Grading Method

At the end of the term you will provide a 7-minute video, in which each member of the project presents a part of the project.

After reviewing your videos, we will invite each group for a 8 mins Q&A. Before the Q&A, we will validate your method on a list of pre-selected departure arrival points, and times of day.

Think of yourselves as a startup trying to sell your solution to the board of a public transport company. Your video is your elevator pitch. It must be short and convincing. In it you describe the viability of the following aspects:

  1. Method used to model the public transport network
  2. Method used to create the predictive models
  3. Route planning algorithm
  4. Validation method

Your grades will be based on the code, videos and Q&A, taking into account:

  1. Clarity and conciseness of the video presentation, code and Q&A
  2. Team work, formulation and decomposition of the problem into smaller tasks between team members
  3. Originality of the solution design, analytics, and presentation
  4. Functional quality of the implementation (does it work?)
  5. Explanation of the pro's and con's / shortcomings of the proposed solution

Dataset Description

For this project we will use the data published on the Open Data Platform Mobility Switzerland.

We will use the SBB data limited around the Zurich area, focusing only on stops within 15km of the Zurich main train station.

We will also provide you with a simulated realtime feed of Istdaten data.

Actual data

Students should already be familiar with the istdaten.

The 2018 to 2022 data is available as a Hive table in partitioned ORC format on our HDFS system, under /data/sbb/part_orc/istdaten.

See assignments and exercises of earlier weeks for more information about this data, and methods to access it.

As a reminder, we provide the relevant column descriptions below. The full description of the data is available in the opentransportdata.swiss data istdaten cookbooks.

  • BETRIEBSTAG: date of the trip
  • FAHRT_BEZEICHNER: identifies the trip
  • BETREIBER_ABK, BETREIBER_NAME: operator (name will contain the full name, e.g. Schweizerische Bundesbahnen for SBB)
  • PRODUCT_ID: type of transport, e.g. train, bus
  • LINIEN_ID: for trains, this is the train number
  • LINIEN_TEXT,VERKEHRSMITTEL_TEXT: for trains, the service type (IC, IR, RE, etc.)
  • ZUSATZFAHRT_TF: boolean, true if this is an additional trip (not part of the regular schedule)
  • FAELLT_AUS_TF: boolean, true if this trip failed (cancelled or not completed)
  • HALTESTELLEN_NAME: name of the stop
  • ANKUNFTSZEIT: arrival time at the stop according to schedule
  • AN_PROGNOSE: actual arrival time (see AN_PROGNOSE_STATUS)
  • AN_PROGNOSE_STATUS: method used to measure AN_PROGNOSE, the time of arrival.
  • ABFAHRTSZEIT: departure time at the stop according to schedule
  • AB_PROGNOSE: actual departure time (see AN_PROGNOSE_STATUS)
  • AB_PROGNOSE_STATUS: method used to measure AB_PROGNOSE, the time of departure.
  • DURCHFAHRT_TF: boolean, true if the transport does not stop there

Each line of the file represents a stop and contains arrival and departure times. When the stop is the start or end of a journey, the corresponding columns will be empty (ANKUNFTSZEIT/ABFAHRTSZEIT). In some cases, the actual times were not measured so the AN_PROGNOSE_STATUS/AB_PROGNOSE_STATUS will be empty or set to PROGNOSE and AN_PROGNOSE/AB_PROGNOSE will be empty.

Timetable data

Timetable data are available from timetable.

You will find there the timetables for the years 2018, 2019 and 2020 and so on. The timetables are updated weekly. It is ok to assume that the weekly changes are small, and a timetable for a given week is thus the same for the full year - use the schedule of the most recent week for the day of the trip.

The full description of the GTFS format is available in the opentransportdata.swiss data timetable cookbooks.

We provide a summary description of the files below:

  • stops.txt(+):

    • STOP_ID: unique identifier (PK) of the stop
    • STOP_NAME: long name of the stop
    • STOP_LAT: stop latitude (WGS84)
    • STOP_LON: stop longitude
    • LOCATION_TYPE:
    • PARENT_STATION: if the stop is one of many collocated at a same location, such as platforms at a train station

  • stop_times.txt(+):

    • TRIP_ID: identifier (FK) of the trip, unique for the day - e.g. 1.TA.1-100-j19-1.1.H
    • ARRIVAL_TIME: scheduled (local) time of arrival at the stop (same as DEPARTURE_TIME if this is the start of the journey)
    • DEPARTURE_TIME: scheduled (local) time of departure at the stop
    • STOP_ID: stop (station) identifier (FK), from stops.txt
    • STOP_SEQUENCE: sequence number of the stop on this trip id, starting at 1.
    • PICKUP_TYPE:
    • DROP_OFF_TYPE:

  • trips.txt:

    • ROUTE_ID: identifier (FK) for the route. A route is a sequence of stops. It is time independent.
    • SERVICE_ID: identifier (FK) of a group of trips in the calendar, and for managing exceptions (e.g. holidays, etc).
    • TRIP_ID: is one instance (PK) of a vehicle journey on a given route - the same route can have many trips at regular intervals; a trip may skip some of the route stops.
    • TRIP_HEADSIGN: displayed to passengers, most of the time this is the (short) name of the last stop.
    • TRIP_SHORT_NAME: internal identifier for the trip_headsign (note TRIP_HEADSIGN and TRIP_SHORT_NAME are only unique for an agency)
    • DIRECTION_ID: if the route is bidirectional, this field indicates the direction of the trip on the route.

  • calendar.txt:

    • SERVICE_ID: identifier (PK) of a group of trips sharing a same calendar and calendar exception pattern.
    • MONDAY..SUNDAY: 0 or 1 for each day of the week, indicating occurence of the service on that day.
    • START_DATE: start date when weekly service id pattern is valid
    • END_DATE: end date after which weekly service id pattern is no longer valid

  • routes.txt:

    • ROUTE_ID: identifier for the route (PK)
    • AGENCY_ID: identifier of the operator (FK)
    • ROUTE_SHORT_NAME: the short name of the route, usually a line number
    • ROUTE_LONG_NAME: (empty)
    • ROUTE_DESC: Bus, Zub, Tram, etc.
    • ROUTE_TYPE:

Note: PK=Primary Key (unique), FK=Foreign Key (refers to a Primary Key in another table)

The other files are:

  • calendar-dates.txt contains exceptions to the weekly patterns expressed in calendar.txt.
  • agency.txt has the details of the operators
  • transfers.txt contains the transfer times between stops or platforms.

Figure 1. better illustrates the above concepts relating stops, routes, trips and stop times on a real example (route 11-3-A-j19-1, direction 0)

journeys

Figure 1. Relation between stops, routes, trips and stop times. The vertical axis represents the stops along the route in the direction of travel. The horizontal axis represents the time of day on a non-linear scale. Solid lines connecting the stops correspond to trips. A trip is one instances of a vehicle journey on the route. Trips on same route do not need to mark all the stops on the route, resulting in trips having different stop lists for the same route.

Stations data

For your convenience we also provide a consolidated liste of stop locations in ORC format under /data/sbb/orc/allstops. The schema of this table is the same as for the stops.txt format described earlier.

Misc data

Althought, not required for this final, you are of course free to use any other sources of data of your choice that might find helpful.

You may for instance download regions of openstreetmap OSM, which includes a public transport layer. If the planet OSM is too large for you, you can find frequently updated exports of the Swiss OSM region.

Others had some success using weather data to predict traffic delays. If you want to give a try, web services such as wunderground, can be a good source of historical weather data.

Hints

Before you get started, we offer a few hints:

  • Reserve some time to Google-up the state of the art before implementing. There is a substantial amount of work on this topic. Look for time-dependent, or time-varying networks, and stochastic route planning under uncertainty.
  • You should already be acquainted with the data. However, as you learn more about the state of the art, spend time to better understand your data. Anticipate what can and cannot be done from what is available to you, and plan your design strategy accordingly. Do not hesitate to complete the proposed data sources with your own if necessary.
  • Start small with a simple working solution and improve on it. In a first version, assume that all trains and buses are always sharp on time. Focus on creating a sane collaborative environment that you can use to develop and test your work in team as it evolves. Next, work-out the risk-aware solution gradually - start with a simple predictive model and improve it. In addition you can test your algorithm on selected pairs of stops before generalizing to the full public transport network under consideration.

FAQ

This section will be updated with the Frequently Asked Questions during the course of this project. Please stay tuned.

1 - Q: Do we need to take into account walking times at the connections?
  • A: Yes, but since we do not have the details of the platforms at each location, we can use a universal formula to come up with a reasonable walking time. We must also allow time for transfers between different modes of transports, such as from bus to tramways. You can use the transfer time information available from transfers.txt from the timetables. Otherwise, we assume that 2min mininum are required for transfers within a same location (i.e. same lat,lon coordinates), to which you add 1min per 50m walking time to connect two stops that are at most 500m appart, on a straight line distance between their two lat,lon.
2 - Q: Can we assume statistical independence between the observed delays?
  • A: Yes, see simplifying assumptions in Problem Description. You will incur no penalty for assuming that the delay of a given train (or other mode of transport, ...), at a given location and time is independent of the delays for all other trains, locations, and times. Even if our experience tells us that this is most of the time not the case. Also, you must assume that you have no real-time delays information at the time you plan your journey, which limits the benefits you could gain by assuming such a dependency.
3 - Q: Can I take advantage of the fact that a connection departs late most of the time to allow a plan that would otherwise not be possible according to the official schedule.
  • A: You may discover that you could take advantage of connections that have a high probability of departing late. However, this is not recommended, or it should come with a warning. Imagine from a user experience perspective, how would you react if you are being proposed an impossible plan in which a transfer is scheduled to depart before you arrive? Furthermore, who would you blame if the plan fails: the planner that came up with a theoretically infeasible plan, or the operator who respected their schedule?