The majority of WIM system outputs are observations of individual vehicle passes or events, including the following data items:
- location information (road, number of lanes, direction of traffic flow)
- vehicle count number
- date and time of vehicle event
- vehicle classification
- vehicle speed
- vehicle axle spacing, wheelbase and length
- IAM, GAM and GVM.
To derive information from the data items above, processing either by the processor and data storage unit or post-collection processing is utilised. Specialised WIM data logging and classification systems, WIM data storage, and WIM data reporting software have been developed. Those WIM data logging and classification systems are generally compatible to multiple types of WIM sensors, and most WIM reporting softwares are WIM system independent and offer a means of making data readily available to the user.
Some European countries were proposing a unified standard database structure for the storage and reporting of WIM data (Austroads 2000). This will permit a common language and use of data across the European continent that is increasingly becoming borderless. The US has developed the LTPP Traffic Database, which has been designed to store, maintain and provide access to not only WIM data, but traffic data generally. The value of these systems is that in addition to storage and reporting, they also offer QA and ongoing calibration abilities.
In Australia, most road agencies have a storage and data reporting system. These systems were generally developed as part of the WIM system and also offer QA and ongoing calibration abilities. They are generally user friendly and accessible, however, they vary between states and territories.
Austroads 2000 reported that since all Australian states and territories have WIM and, to varying degrees, handling and storage systems catering for their specific needs, it would be inappropriate to impose a new system on the entire data storage process. Rather, it seems more realistic, that at the national level, different levels of aggregation of WIM data output should occur so as to develop different application-based reports. This would have the additional benefit of creating uniform and standard application reports for all users.
As mentioned, vendor validity codes are assigned to vehicle record events where there was a problem with sensor detection/failure, acceleration, straddling, minimum speed, classification, or sensor count mismatch, etc. A good practice in preparing reports which ultimately may be politically sensitive is to filter out vehicles from the data set that have been assigned certain validity codes.
Austroads 2000, Weigh-in-motion technology, AP–R168-00, Austroads, Sydney, NSW