Network Strategy

A WIM strategy should consider the following:

  • What is the purpose of WIM data, whether it will be primarily used for planning and asset management purposes, or for enforcement of illegally overloaded vehicles including on toll roads or a combination of purposes. The purpose of the data will influence the type of sites, permanent, portable etc, their number, location and type of technology.
  • Opportunities to integrate WIM with other technologies such as Automated Vehicle Identification Systems.
  • A plan and methodology for determining network coverage in terms of site location, number and type. Current practices of road agencies in Australia and New Zealand indicate that WIM sites are installed on major freight routes, roads providing access to major ports, major cities and interstate and interregional routes. The required number of sites is determined by assessing the statistical sample size (e.g. 90% confidence level with ±10% accuracy) and establishing 'truck weight groups'. Some criteria for defining truck weight groups include: geographic groups (agricultural, industrial, trade etc.), functional classification and truck volume.
  • The technologies available, their strengths and weaknesses/characteristics relevant for the required purpose.
  • The equipment's full life cycle costs (installation, calibration and maintenance).
  • The cost of the systems used for data processing and reporting including QA systems and processes.
  • A staged plan for implementation including integration with road design, construction and maintenance processes to minimise installation and ongoing maintenance costs.
  • Staff numbers and skills requirements including training expenses.
  • Justification and feasibility.
  • Opportunities to incorporate costs into and link to other corporate programs or initiatives such as long term pavement performance, enhancement of safety and air quality, Safe Systems, weight enforcement etc.
  • Contribution of WIM sites to traffic data collection program (volume, classification, speed) as additional permanent traffic counting sites.
  • A time horizon of 5-10 years. Because the cost of implementing a WIM strategy, although offset by the benefits, is significant. Also the implementation of the strategy may require few years and therefore it is recommended to develop a strategy that addresses each agency's needs over a considerable timeframe in the future.

 


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