The question of what length of time is necessary to collect statistically reliable vehicle classification data is an important issue when manpower is limited. Varying local conditions may necessitate more classification data be collected at some locations than others. The use of short-term counts could produce significant savings. Supplementing manual counts with automatic classification equipment could reduce data collection costs and improve accuracy.

The objectives of this study were to review literature to determine the capabilities of automatic classification equipment and to analyze toll road data in Kentucky to determine if short time periods may be used to represent the annual distribution of vehicle types.

Automatic classification equipment has been evaluated by others and there are systems available that can classify vehicles according to number of axles and wheelbase. Emphasis is being placed on the development of a more reliable and permanent axle counter by several companies.

Results from the analysis of vehicle classification data at two parkway toll stations indicate that specific 8-hour periods within the year are representative of the annual distribution of vehicle types. It was recommended that data collection efforts be concentrated on weekdays between 7:00 a.m. and 11:00 p.m. during all seasons of the year. Limitations were noted because the analysis included data from only two toll stations.

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The contents of this report reflect the views of the author who is responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the University of Kentucky, the Kentucky Transportation Cabinet, nor the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. The inclusion of manufacturer names and tradenames are for identification purposes and are not to be considered as endorsements.