Assessing Vehicle Air Pollution Emissions
National Institute of Water & Atmospheric Research Ltd, July 2008
This report presents the outcomes from the project "New Assessments of Vehicle Air Pollution and Health Effects using Advanced On-Road Remote Sensing Technology" (CARP) - project reference number 36.
This project involved a programme of roadside vehicle exhaust emissions measurements, followed by an analysis of the field data. The vehicle emissions were monitored using a remote sensing device (RSD), which measures emissions in approximately half a second as the vehicle drives through a roadside monitoring site. The RSD measures four tailpipe pollutants: Carbon monoxide (CO), hydrocarbons (HC), nitric oxide (NO) and uvSmoke (a proxy for particulate emissions). Evaporative emissions were not measured. This project provided for the first time, a large, detailed and sophisticated database of on-road emissions of Australian vehicles. Data were used to analyse the sources of air pollution by vehicle age, fuel type, usage and engine size. The results of this analysis were used to refine estimates of health effects associated with vehicle emissions.
Valid emissions measurements were obtained from approximately 53,000 vehicles during the monitoring programme, 22,000 in Brisbane, 10,000 in Perth and 21,000 in Sydney. Approximately 89% of the monitored fleet were petrol vehicles, 8% were diesel and the remaining 3% were gas or dual-fuel (gas and petrol).
The average age of the vehicles in the sample fleet is 6.9 years old (manufactured in 1998-1999) which is three to four years newer than the average age of all vehicles registered in Australia (10 years).
Petrol and gas fuelled vehicles have higher CO emissions than diesel fuelled vehicles, while gas fuelled vehicles have higher HC emissions than petrol or light duty diesel vehicles. Diesel powered vehicles have higher NO emissions and uvSmoke measurements than petrol and gas fuelled vehicles. Emissions of all four pollutants increase with increasing age of petrol vehicles, as do emissions of CO, HC and uvSmoke from diesel vehicles. The emissions of NO do not appear to vary significantly with the age of diesel vehicles.
Private or family owned vehicles tend to have higher CO, HC and NO emissions than vehicles that fall under other ownership categories (mainly commercial), while uvSmoke measurements are similar for both ownership categories.
Emissions were found to vary with vehicle speed, acceleration and power. A comparison between the emissions of congested and free-flowing vehicles showed that emissions of all four pollutants increased significantly under congested driving conditions.
Emissions for all four pollutants are dominated by a small number of gross emitting vehicles. The 'most polluting' 10% of vehicles are responsible for about 70% of CO emissions, 60% of uvSmoke and HC emissions and about 50% of NO emissions. On the other hand, the cleanest 60% of the fleet contribute less than 10% of the total emissions for each pollutant.
The data obtained from the remote sensing programme have been used to estimate the air pollution health effects and costs from the tail pipe emissions from vehicles travelling along a typical busy roadway. The health effects results using the remote sensing emission factors are up to 175% greater than those using the Australian Design Rules (ADR) factors. The case study demonstrates that the choice of tail pipe emissions factors is a critical step in health effects assessments and that it is highly desirable to use the most reliable information available.
This programme has generated a large number of benefits beyond those specifically contracted. There has been considerable interest from stakeholders in this project. This included ministerial press releases, a community awareness day and a number of newspaper articles. The RSD vehicle emissions programme has very useful synergies with, and is complementary to, a number of other vehicle emissions programmes being undertaken in Australia.
The vehicle emission database that has been generated by this programme has a significant number of additional uses beyond the contracted outputs of this programme. Potential benefits of running future vehicle emission programmes using the RSD have been identified. This on-road vehicle emissions programme has been completed successfully and the aims and objectives of the project have been met. The field monitoring programme was completed without incident and has demonstrated that the equipment can be used safely and effectively in Australian cities.
The outcomes of the project have resulted in a better understanding of the Australian vehicle fleet emissions and their implications for health effects, along with a new and advanced database of real-world on-road vehicle emissions. Although the field programme was carried out in three cities (Brisbane, Perth and Sydney) the results are believed to be widely applicable across all Australian cities.