An Open-Architecture GIS Component for Creating Multiband Traffic Density Maps

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October 15, 2012

An Open-Architecture GIS Component for

Creating Multiband Traffic Density Maps

INFORMS Annual Meeting

Phoenix, AZ

David Hunt (presenting author)

Francis Julian

Ming Lu

Marc Meketon

Carl Van Dyke

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Acknowledgements

• The concept for an open architecture GIS component began with

discussions between CSX Technology and Oliver Wyman.

• The designs and concepts presented in this document, along with any

errors or omissions, are the sole responsibility of the authors.

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Introducing the traffic density map

Charles Joseph Minard’s 1864 map of French wine exports is an early example of a traffic density map. The inset drills down into wine export quantities over time.

Computers have been used for decades to draw traffic density maps, but have we fully leveraged the potential or made them as ubiquitous as they should be?

Source: Edward Tufte, “The Visual Display of Quantitative Information,” Graphics Press, Cheshire, CT, 1983, page 25. Image from http://www.edwardtufte.com/.

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Motivation and design goals

Oliver Wyman was unable to find a packaged solution that generated multiband traffic density

maps and was easy to integrate into other software products

• Motivation

– Network based volume files contain millions of records and numerous attributes

– Railroads, trucking companies, airlines, utilities, manufactures and countless other industries that move items across a network need better tools to understand the impacts of link volumes and location volumes – Visualization is one of the best tools for acquiring information from data

– Traffic density (flow) maps are useful, but not always quick and easy to generate, and they are often designed for integration into a specific software product

• Design goals

– Must be easy to use

- Changes to scale, color, labels, and other displayed items should be done directly on the map - An occasional user should be able to generate a multiband traffic density map

– Must be dynamic

- Pan, zoom and quick identification of locations and volumes

- Layers can be turned on and off by showing or hiding different map items

- Drilling down into the underlying link and location data should reveal traffic details

- Allow filtering on dates and volume attributes (load/empty, commodity, line of business, etc.) – Must be accessible

- Open architecture to allow integration with other software products (BI, DW, forecasting, planning, etc.) - Web-based to allow broad use throughout a company

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Our solution has two primary components: the Link Density Calculator; and,

the Traffic Density Mapper.

• The Link Density Calculator (LDC) is a traffic assignment algorithm that:

– Routes an origin-destination based traffic file over a network

– Calculates the volume on each link and at each node

– Creates “trace-back” tables that support interactive drilling down into the link and node data

– Uses selected “vias” to route traffic over the correct routes

• The Traffic Density Mapper (TDM) creates high quality geographical displays with:

– A Web Control that allows changing color, scale, and turning on/off different map layers

– A Web Service that generates:

- Multibands displaying volumes on network links

- Pie-charts displaying activity at network nodes

- Combination multiband and pie maps

• The TDM and LDC components are based on an open architecture that allows integration with

other software products. The other software products need to provide:

– Network: nodes, links, link costs

– Volumes: origin, destination, “vias,” attributes, quantity

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5 5 © Oliver Wyman

Base map with network links and the Traffic Density Mapper control

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Enabling the flow band (traffic density) layer

Legend displays band descriptions and scale. A scale of miles is in the lower left.

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7 7 © Oliver Wyman

Enabling the location volumes (pies) on top of the link densities

Note that the Node Volumes layer was moved above the Links layer so pies draw on top of links.

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Enabling the location labels and the link volume labels

TDM automatically labels nodes and links, which the user can override using “Ctrl – click.”

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9 9 © Oliver Wyman

Location volume view

Link Volumes, Labels and Nodes have been disabled.

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Close-up view of link volume and location volume map

Can zoom using the mouse wheel, or by using the slider bar adjacent to the TDM control.

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Supports a “roll-over” capability

Temporarily display link and location names by “hovering” mouse over the map element.

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Location name temporarily displayed by “hovering” with mouse

To retain the label, use “Ctrl – click”

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Highlighting link volumes by “hovering” mouse

Can interact with the map to identify volumes on any link.

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Link volume drill-down process

Can identify the traffic or trains moving over any network link.

Drill down software still under development.

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Highlighting location volumes by “hovering” mouse

Can interact with the map to identify volumes at any location.

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Location volume drill-down process

Can identify the traffic or trains at any network location.

Drill down software still under development.

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The various pieces are draw separately and then combined.

The control box (used to change colors, scale, and turn layers on and off) is written in

JavaScript. The other pieces are images (.png files), which can be overlaid.

Pies

Legend /

Scale

Controls

Title

Base map

Multibands

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IIS Web Server Data Service TDM Web Service Link Density Calc.

Generic Web Server:

• The application is the existing software product that will use the LDC and TDM. It must be accessible from a browser and it will require adding a proxy to interact with the Map Server and the IIS Web Server.

• The TDM Web Control is a JavaScript program that provides map controls for changing colors, turning on/off layers, etc.

IIS Web Server:

• The TDM Web Service generates the multibands and pies that will be

displayed on the map.

• The Link Density Calculator assigns traffic to the network, and generates a link density table with trackbacks that allows interactive “drilling down” into the data behind the maps.

• The Data Service extracts network and volume files from the database, and writes trace-back and other files as

Traffic Density Mapper Architecture (1 of 2)

Communication path sequences are routed through a Generic Web Server to allow other services

to reside behind fire walls. A proxy is used to access the ESRI Map Server and IIS Web Server.

Client Browser

Generic Map Server

Oracle or Other Database Web Page

Generic Web Server Java or .NET

Application with Proxy

TDM Web Control

Base Maps (ESRI ArcGIS or other)

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Client Browser:

• Currently set up for Internet Explorer 8 or newer version, but eventually can be called through any popular

browser.

Generic Map Server:

• This is initially an ESRI ArcGIS server, but can be any program providing background map images.

Oracle or Other Database:

• Currently uses an Oracle database to extract network and volume files, and write trace-back, link density, location volume or other files if necessary. These files are extracted through the data service, which allows different data services to be written for

databases other than Oracle.

Traffic Density Mapper Architecture (2 of 2)

The architecture will allow any popular browser, map server and database to be used.

Client Browser

Generic Map Server

Oracle or Other Database Web Page

Base Maps (ESRI ArcGIS or other)

IIS Web Server

Data Service TDM Web Service Link Density Calc.

Generic Web Server Java or .NET

Application with Proxy

TDM Web Control

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TDM “Hello, World!” equivalent: the most basic TDM application

Editing this HTML file will provide a TDM web page that can be integrated into existing business

intelligence, forecasting, planning, or other software.

To create the basic TDM application

1. Copy the following HTML page and edit below.

2. Populate the data source with your map data. Data source could be Oracle, Excel, Access, other. 3. Add this web page to your application.

Filters and controls can be added to provide the user with more flexibility

A) Edit Web Address

of Map Server

B) Edit Web Address

of Data Server

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The required inputs are a network and a volume file

The Link Density Calculator can generate the link density, location volume, and

trace-back files, or these files can be supplied by the calling application.

Network File Volume File Location Volume

File

Track-Back File Link Density File

A basic network and volume file are required, but the attributes listed above are provided as

examples. They will vary based on the available data and the application.

• Locations (nodes) – Unique identifier (e.g.,

milepost) – Name – Latitude / Longitude – Attribute (e.g., intermodal yard) • Links

– A node and B node – Distance

– Direction – Routing penalty

(impedance)

– Routing category (bulk, intermodal, hazmat, etc.)

• An origin / destination based volume file containing: – Date

- Trip start and/or end - Forecasted date – Units - Railcars - Trains - Trucks - Packages - Tons – Attributes - Load / Empty - Line of business - Commodity – Via locations - A set of nodes specifying the path taken

• A traffic assignment algorithm (e.g., LDC ) routes the Volume File over a network, summing the moves on each link • The Link Density File

contains one row for each link in the network, where volume >0. • The Link Density File

contains directional volumes by attribute – The attributes are

aggregated , forming the groups used for multiband traffic density maps – Volumes are maintained separately by direction, allowing traffic imbalances to be identified

• The Location Volume File is a node-based file containing the amount of:

– Originations – Terminations – Work done - Block swap - Sorting - Cross-docking – Passing through without work • Identifying originations and terminations is straight forward, but identifying if work is done requires additional information:

– Work done at location – Assumptions about

which volume attributes trigger a work event

• Provides a matching between the O/D based Volume File and the Link Density File.

– Standard traffic assignment algorithms do not maintain the ability to go back to the O/D file from the link density file

• Allows the maps to be interactive by providing drill downs into the original volumes – Identify the specific

traffic moving over a link

– Identify the specific traffic originating, terminating, or passing through a location

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