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INTRODUCTION

The publication presents estimates from the 2001 Survey of Motor Vehicle Use (SMVU). The data were collected in four quarterly sample surveys conducted by the Australia Bureau of Statistics (ABS) over the period 1 November 2000 to 31 October 2001. Revised estimates from the 2000 SMVU are also included in this publication. These relate to the period 1 November 1999 to 31 October 2000. Estimates in this publication have been produced by employing post-stratification to correct for population frame deficiencies. Detail on this process can be found in Technical Note 2: Methodological Review.

SCOPE

The scope of the survey is all vehicles that were registered with a motor vehicle authority for road use at some stage during the 12 months ended 31 October 2001. Not included are caravans, trailers, tractors, plant and equipment, vehicles belonging to the defence services and vehicles with diplomatic or consular plates. Where they were registered as such, vintage and veteran cars were also excluded from the survey. The population was identified using information obtained from the state and territory motor vehicle registration authorities.

METHODOLOGY

For the 2001 SMVU, a sample of approximately 17,000 vehicles was selected to report on vehicle use over a three-month period within the reference year 1 November 2000 to 31 October 2001. Of these, 25% were passenger vehicles and motor cycles, 59% were freight vehicles, 11% were buses and 5% were other non-freight carrying vehicles. The sample size was chosen to give a suitable level of precision for estimates of total distance travelled and tonne-kilometres for each state/territory of registration by type of vehicle category.

The survey methodology is described as pre-advice, where owners of vehicles selected in the survey received early advice about their inclusion to encourage record keeping and minimise reliance on recall. These owners were asked to complete two mail questionnaires tailored to their vehicle type. The first, at the beginning of each quarterly survey period, asked for selected vehicle characteristics and the vehicle's odometer reading. Owners were also advised that they would receive a follow up questionnaire at the end of the quarter seeking details about the use of the vehicle over the quarter and a second odometer reading. Examples of the main items requested in the second questionnaire were included with the first questionnaire.

When questionnaires were returned to the ABS they were checked for completeness and accuracy and, where possible, follow-up contact was made with owners to resolve reporting problems. Where contact with providers could not be made, missing items on incomplete questionnaires were filled by imputing average data from like vehicles for which data were obtained.

Where the selected vehicle owner had not owned the vehicle for the whole quarterly survey period, the details provided for the period of ownership were adjusted to give a three-month equivalent, except where the vehicle was deregistered, in which case only the use up to the date of deregistration was included.

In addition, adjustments were made in the estimation process to account for the use of new motor vehicles registered after the survey population was identified, as well as the re-registration of other vehicles during this time. More information about these adjustments is provided in Technical Note 1: Data Quality.

Estimates from information reported in each quarterly collection period were produced and these were then aggregated into annual estimates relating to the use of vehicles during the period 1 November 2000 to 31 October 2001. The size of the sample is insufficient to produce reliable quarterly results.

RELIABILITY OF ESTIMATES

When interpreting the results of a survey it is important to take into account factors that may affect the reliability of estimates. Such factors can be classified as either sampling error or non-sampling error. Information on sampling and non-sampling error is provided in Technical Note 1: Data Quality.

COMPARISON WITH MOTOR VEHICLE CENSUS DATA

Survey estimates of the numbers of vehicles, by vehicle type, are not fully comparable with ABS Motor Vehicle Census data (see Motor Vehicle Census Australia, (cat. no. 9309.0)). The main differences are:

• survey estimates of the numbers of vehicles relate to the average number of vehicles registered for road use during the period 1 November 2000 to 31 October 2001, not to the number of vehicles registered at a specific date, as is the case for the Motor Vehicle Census

• the characteristics of the type of vehicle identified from the survey information may differ from those recorded by the motor registries.