Pavement construction: lifetime impacts of short term decisions N. Mithraratne 1 and R Vale 2 1 National University of Singapore, Singapore, akimnsm@nus.edu.sg 2 Victoria University of Wellington, Wellington, New Zealand, r.vale@vuw.ac.nz Background Transport facilitates socio-economic activities by providing a direct link between various parties and affects all aspects of modern life either directly or indirectly. Most discussions on sustainability concentrate on the transport mode and fuel use irrespective of whether it is passenger or freight transport that is being considered. This could be regarded reasonable as fuel use for land transport is significant in the annual energy expenditure of most countries and has been steadily increasing. While the UN reported a 12% increase in global CO 2 emissions due to transport between 2000 and 2005, 19% of New Zealand’s total greenhouse gas (GHG) emissions in 2009 were also due to fuel combustion in the transport sector [1, 2]. Given the threat of climate change and the uncertainty surrounding oil supply, the current practices will not be economically or environmentally sustainable. Once constructed, the pavements on which land vehicles travel lock in resources (land and materials) for a very long time. International studies have estimated that up to 65% of total energy and emissions associated with passenger and freight transport result from indirect sources such as transport infrastructure, vehicle manufacture and fuel extraction [3, 4]. GHG emissions due to a kilometer length of a single pavement lane could vary from 80 to 500tCO 2 e over a 50 year period, with energy losses through tyre-pavement contact (known as rolling resistance), traffic delays, construction materials used, and material transportation being the main factors determining lifetime emissions [5]. Therefore the decisions on how pavements are constructed and maintained could be of utmost importance. New Zealand studies on pavement construction so far have been either limited to a single phase of pavement life (construction) [6] or to the use of alternative construction materials [7, 8]. Introduction New Zealand roads use two main construction types; flexible unbound granular pavements (90% of the total length) and rigid structural asphaltic pavements. The predominant surface finish used on unbound granular pavements is chipseal [9]. Due to the less than optimal population density many lightly-used rural roads 1 use unbound granular construction with a loose surface finish. This less costly construction, however, requires regular maintenance in terms of smoothing the surface and replenishing the washed away chips. Used on a rural road carrying 100vehicles/day, loose surface finish requires smoothing the surface four times a year and replenishing a 15mm thick layer of chips annually [10]. The total length of bridges in the New Zealand road network represents less than 2% of the total length of roads. An Australian study, considering a road project involving new build and rehabilitation and a motorway interchange bridge, which can be regarded as an extreme case, estimated GHG emissions for bridges to be as high as 38 times the emissions of pavement [11]. Although the resource use for bridges could be noteworthy, construction and maintenance data on New Zealand bridges are not available. This paper evaluates the externalities, lifetime energy and carbon, associated with pavement construction practice in New Zealand. Methodology This study, which uses product-based life cycle assessment, is limited to the pavement and excludes the other support structures, such as barriers, streetlights, footpaths, signs, etc. The impact of traffic delays and rolling resistance on the lifetime performance is not considered. Pavement life stages analysed include construction (pavement formation (earth works), base layers, surface finishes), maintenance and operation over a 40 year period. As demolition and disposal of roads is uncommon, they are not considered. On-site wastage of construction materials is considered to be minimal 1 32% of the total road lane length has a loose surface finish.