Traffic Management System Using Java


The goal of this assignment is to implement a set of classes and interfaces1 to be used to create a simulation of a traffic management system. You will implement precisely the public and protected items described in the supplied documentation (no extra public/protected members or classes).

Private members may be added at your own discretion.

Language requirements:

  • Java version 13,

  • JUnit 4


In this assignment you will finish building a simple simulation of a traffic management system (TMS). A traffic management system monitors traffic flow in a region and adjusts traffic signals to optimise traffic flow. A TMS uses different types of sensors and signals to monitor and manage traffic flow. In the first assignment you implemented the core model for the TMS. In the second assignment you will implement some of the more advanced logic to provide a very simple simulation for the TMS.

In addition to the pressure pads and speed cameras from assignment one, you willl add a vehicle count sensor. It counts vehicles passing a location and reports the traffic flow as the number of vehicles in a time period. You need to integrate this new type of sensor into the system. This is an example of a common situation when building a large system. New features need to be added to the system. A well designed system that uses interfaces to define an API means it should be simple to add the new feature.

In assignment one, you implemented traffic lights and electronic speed signs and attached them to a route. In assignment two you will provide logic to coordinate traffic lights at intersections.

The TMS monitors sensors along routes and manages signals on routes, and at intersections, to optimise traffic flow. In assignment one, the network of routes was implicitly defined by your test code and SimpleDisplay. In assignment two you will implement the logic for the TMS to maintain a network of routes. This includes the ability to load a network from a data file and save a modified network to a file.

Monitoring and managing congestion requires sophisticated logic in a real TMS. In assignment one congestion was simply reported by each sensor. In assignment two you will implement logic for congestion calculators. These take the congestion data from a set of sensors and determine overall congestion for the route(s) covered by the sensors.

The approach taken is to define a CongestionCalculator interface that provides an API. Different classes can implement this inter- face to provide different options for the logic of determining congestion. This is another example of a common approach to designing flexibility into the system’s structure.

When implementing the assignment you need to remember that it is implementing a simulation of the TMS and not the real TMS. Interfaces are provided for the sensors to allow easy replacement of sensor implementations in the program. You will not be collecting data from real sensors but will be implementing classes that demonstrate the behaviour of sensors. They store a set of data values that are used to simulate the sensors returning different values over time. Signals are simple simulations of real signals, in that they only store the current state of the signal and allow the route to update the signal.

To manage simulation of time, there is a TimedItem interface and a TimedItemManager class, which you implemented in assignment one. Sensors implement the TimedItem interface, as they are items which need to react to timed events. TimedItemManager stores all the TimedItem ob- jects in the application. The simulation’s GUI tracks time passing in and it invokes MainViewModel.tick() once per second. The tick method calls the TimedItemManager’s oneSecond method, which sends the oneSecond message to all TimedItems. This approach of tracking the passage of time and invoking an action on all relevant objects once per second was the reason that TimedItemManager is implemented as a singleton2


A simple GUI has been provided to you as part of the provided code. It is in the tms.display package. It will not work until you have implemented the other parts of the assignment that it uses.

The GUI has been implemented using JavaFX and consists of three classes and an enum. MainView creates the main window for the TMS GUI. StructureView displays the structure of the traffic network. MainViewModel represents the TMS model that is to be displayed. The TMS application is initialised and started by the Launcher class in the tms package. It loads the traffic network data and creates the GUI. Most of the GUI code has been provided to you. In MainViewModel you need to implement some of the logic that is executed by events in the simulation and to handle keyboard input for the main application’s window.

The functionality you need to implement in MainViewModel is to:

  • Save the state of the network to a file in response to the user selecting the save command.

This is to be implemented in

  • Allow the simulation’s execution to be paused and unpaused. This is to be implemented in MainViewModel.togglePaused().

  • Process time passing in the simulation. This is to be implemented in MainViewModel.tick().

Keyboard input is handled by the accept method in the MainViewModel class. It needs to process input from the user in the main window to perform actions in the simulation. Pressing the ‘P’ key will toggle whether the simulation is paused or not. The ‘Q’ key will quit the simulation.

The ‘S’ key will save the current network to a file called “DefaultSave.txt”. A shell for this method has been provided because it is already hooked into the GUI.

Persistent Data

You need to implement loading a network from a data file. The JavaDoc for the loadNetwork method in the NetworkInitialiser class describes the format of a network data file. Saving a network is done by the save method in the MainViewModel class. A network data file is structured as follows:

  • The first line is the number of intersections (ni) in the file.

  • The second line is the number of routes in the file.

  • The third line is the duration of a yellow light.

The following ni lines are the intersection details.

  • The first part of an intersection line is its id.

  • This is optionally followed by a ‘:’, a duration, another ‘:’, and a sequence of intersection ids which are separated by commas.

The final set of lines are the route details, including any sensors on the routes.

– Each route is on a separate line. The sensors for a route are on the lines immediately

after the line for the route.

– A route is described by the id of the from intersection, followed by a ‘:’, then the id of

the to intersection, followed by a ‘:’, then the default speed for the route, followed by a

‘:’, then the number of sensors on the route, then optionally a ‘:’ and the speed of the

electronic speed sign on the route if it has one.

– If the route has any sensors, each sensor follows on separate lines.

– The first part of a sensor line is its type ‘PP’, ‘SC’ or ‘VC’. This is followed by a ‘:’,

then its threshold value, a ‘:’, and then a comma separated list of the data values used

to simulate the data returned by the sensor.

  • Any line that starts with a semi-colon ‘;’ is a comment and is to be ignored when reading the data from the file.

  • Attempting to read an invalid network data file should throw an InvalidNetworkException.

An example data file, called demo.txt, is provided in your repository in the networks directory. It corresponds to the diagram below.

Supplied Material

  • This task sheet.

  • An example network data file.

  • Code specification document (Javadoc)

  • A Subversion repositiory for submitting your assignment called ass2.

  • A simple graphical user interface for the simulation, which is in the display package.

  • A sample solution for the first assignment. You are to use this as the base for your implementation of the second assignment. As the first step in the assignment you should create a new project by checking out the ass2 repository from Subversion.


Code specifications are an important tool for developing code in collaboration with other people. Although assignments in this course are individual, they still aim to prepare you for writing code to a strict specification by providing a specification document (in Java, this is called Javadoc). You will need to implement the specification precisely as it is described in the specification document.

The Javadoc can be viewed in either of the two following ways:

1. Open in your web browser. Note that this will only be the most recent version of the Javadoc.

2. Navigate to the relevant assignments folder under Assessment on Blackboard and you will be able to download the Javadoc .zip file containing html documentation. Unzip the bundle somewhere, and open docs/index.html with your web browser.

Tags in the Javadoc indicate what code has been implemented in assignment one and what code you need to implement in assignment two. Some code from assignment one will need to be modified. There are tags indicating places where you can expect to modify the assignment one code but these are not guaranteed to be all of the places where you may end up modifying code from assignment one.


1. Implement the classes and methods described in the Javadoc as being requried for assignment two.

2. Implement the indicated features of the user interface.

3. Write JUnit 4 tests for all the methods in the following classes:

  • AveragingCongestionCalculator (in a class called AveragingCongestionCalculatorTest)

  • IntersectionLights (in a class called IntersectionLightsTest)

  • NetworkInitialiser (in a class called NetworkInitialiserTest)


Submission is via your Subversion repository. You must ensure that you have committed your code to your repository before the submission deadline. Code that is submitted after the deadline will not be marked. Failure to submit your code through your repository will result in it not being marked. Details for how to submit your assignment are available in the Version Control Guide.

Your repository url is: — CSSE2002 students

or — CSSE7023 students

Your submission should have the following internal structure:

src/ folders (packages) and .java files for classes described in the Javadoc

test/ folders (packages) and .java files for the JUnit test classes

A complete submission would look like:



































Ensure that your assignments correctly declare the package they are within. For example, should declare package tms.congestion.

Do not submit any other files (e.g. no .class files). Note that AveragingCongestionCalculatorTest, IntersectionLightsTest and NetworkInitialiserTest will be compiled without the rest of your files.

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