Data methodology

UN Global Compact

Throughout this report we have communicated our progress against the 10 principles of the United Nations Global Compact. The Global Compact is the largest corporate responsibility initiative in the world, with more than 10,000 participants from more than 130 countries. Transurban became a signatory to the Compact in 2009.

Currency and conversion

All financial amounts are reported in Australian dollars unless otherwise stated. Figures in USD may have been converted to AUD using the exchange rate at 30 June 2015 (1 AUD: 0.768 USD).

GHG emissions

Transurban uses The Greenhouse Gas Protocol: A Corporate Accounting and Reporting Standard (Revised Edition) to draw boundaries around emission sources when quantifying our Scope 1, Scope 2 and Scope 3 GHG emissions. Emission factors and calculation methodologies outlined in the Australian Government Department of Climate Change - National Greenhouse Accounts (NGA) Factors December 2014 are then applied to each data source.

For our US operations, we calculate Scope 1 GHG emissions using emission factors and calculation methodologies outlined by the US Environmental Protection Agency (EPA) for the calculation of GHG emissions from transportation and mobile sources.

The EPA’s eGRID2010 Ninth edition with 2010 data (released February 2014) is used to calculate Scope 2 and 3 GHG emissions from electricity in the US.

Transurban applies the GHG Protocol‘s air travel method and emission factors to individual flight details to generate our Scope 3 emissions associated with corporate air travel.

Australian Government NGA Factors December 2014 have been used to calculate Transurban’s Scope 3 emissions from waste, fuel use (for incident response and operations and maintenance vehicles), fuel refining and transport and electricity transmission and distribution losses.

Customer travel

GHG emissions from our roadways were calculated using Transurban’s traffic model (developed in-house). The model uses traffic data that is extracted from our tolling system and represents actual trips along the roadway. The tolling system records information such as vehicle class and entry and exit points of vehicles, giving an accurate representation of vehicle types and trip lengths. Supplementary information on some assets includes vehicle origin-destination studies for typical travel routes, independent travel time studies, and assumptions based on the physical dimensions of assets. This data is used to calculate the total Vehicle Kilometres Travelled (VKT) on each asset for the year.

(Note: VKT is also used in our Road Injury Crash Index (RICI) for safety reporting. However, since this metric is regularly monitored by Transurban throughout the year before tolling data is finalised, the estimated VKT used in safety figures relies on extrapolation. Customer emissions are compiled only at end-of-year with full data. This means that a slightly different VKT estimate method is used in safety figures and emissions figures. Transurban is working towards using a consistent estimate of VKT for both purposes.)

Travel speeds are an additional contributing factor in calculating GHG emissions. Our tolling systems on some of these roads time stamp each transaction, so it is possible to estimate average travel speeds for each individual trip. For roads with only single toll points – such as the Eastern Distributor – we have used surveyed average travel speeds.

Fuel type is also important in the calculation of GHG emissions. Vehicle fuel type is estimated from information on fleet mix and fuel type for each state and city documented in the 2014 Australian Bureau of Statistics (ABS) motor vehicle census.

Transurban’s in-house traffic model uses the above information and applies emission factors sourced from the University of South Australia that are sensitive to average travel speeds to calculate the GHG emissions from customer vehicles on the specified Australian roads.

GRI G4 Indicators

  • EN15
  • EN16
  • EN17