Bridges

Access regimes typically incorporate a set of rules imposed on a heavy vehicle (axle spacing and axle mass) to ensure that bridges operate within safe limits. The current Heavy Vehicle National Law (HVNL), gazette notices and the Performance Based Standards (PBS) scheme are all underpinned by this approach.

These prescriptive rules offer vehicle designers certainty but allow little room for innovation. Given the increasing demand for greater productivity, road managers are required to consider each application vehicle against their structures (bridges) and roads before access can be granted. Existing access regimes are highly inefficient and require significant human effort and resources to deliver these gains for industry.

This paper summarises Tasmania’s Heavy Vehicle Access Management System (HVAMS), which offers an entirely new approach to facilitating access for heavy vehicles and has been selected to be the basis of Australia’s National Automated Access System (NAAS). The principles of granularity, consistency and transparency are also discussed.

The paper also discusses one of the key components of the next version of HVAMS, which is the assessment of each structure based on the comparison of load effects produced by an application vehicle against defined load effect limits. This is enabled by a Load Effect Generator (LEG), which calculates load effects at defined locations on a series of line beam models. The assessment logic is performed by the system within seconds and incorporates the considered risk appetite applied to individual structures by the road manager.