PBS road and bridge access

Mass limits 

Under the Performance-Based Standards (PBS) scheme, axle group types and mass limits are identical to those allowed under existing General Mass Limits, Concessional Mass Limits and Higher Mass Limits schemes, available from the National Transport Commission website. 

Operating conditions for these schemes also apply to PBS vehicles. Gross combination mass is not limited by this standard, but may be limited indirectly by the bridge loading and safety standards. 

The Network Classification Guidelines presently limits General Access vehicles to a gross mass of 50 tonnes. A 50.5 tonne mass limit is also possible by having 6.5 tonnes on the steer axle providing the motor vehicle complies with certain conditions. 

Recommended network length limits for PBS heavy vehicles also apply. 

Maximum overall length limits 

The PBS road network has been classified into four levels: 

  • Level 1: Similar to General access
  • Level 2: Similar to B-double routes
  • Level 3: Similar to Double (Type I) road train routes
  • Level 4: Similar to Triple (Type II) road train routes 

The recommended maximum overall lengths for each level are described below.

Vehicle performance level

Network access by vehicle length, L (m)

Class ‘A’

Class ‘B’

Level 1 L ≤ 20 (General access*)
Level 2 L ≤ 26 L ≤ 30
Level 3 L ≤ 36.5 L ≤ 42
Level 4 L ≤ 53.5 L ≤ 60

*General Access is subject to a 50.5 tonne gross mass limit, posted local restrictions and restrictions or limitations specified by the road authority. 

Bridge access 

The effects caused by a vehicle in the PBS scheme on any bridge on the route/network requested shall be limited by either of the following methods (‘tiers’). Note that each successive tier may allow greater gross mass and may reduce the extent of network access. 

Tier 1 - General access or Restricted access
Must meet the bridge formulae listed in Section A4.5 of the PBS Scheme Standards and Vehicle Assessment Rules 

Tier 2 - Special access
Must not cause greater effects than those caused by existing commercial vehicles acceptable to the bridge owner. 

Tier 3 - Specific link access
Approval by the owners of the bridges to use all of the bridges on a specific link based on detailed individual bridge assessment. Any combination that uses quad axles will automatically be subjected to a Tier 3 assessment. 

Bridge Formulae (Tier 1) 

The minimum distance, L (metres), between the extreme axles of any two axle groups – for a given total gross mass, M (tonnes), on the axles within that distance – is controlled by the relevant bridge formula. The absolute minimum internal distance allowed between any two axle groups is 2.5 m. Existing clear space rules apply to minimum clear distances between axle groups on B-doubles. 

For vehicles operating under the Concessional Mass Limits scheme, axle groups are to be treated as though they are laden to General Mass Limits. Higher Mass Limits vehicles will only have access to portions of the road and bridge network that the jurisdiction considers to be suitable for Higher Mass Limits vehicles. 

Access to the PBS Level 1 road network
M = 3L + 12.5 for M <= 42.5 t and M = L + 32.5 for M >= 42.5 t

Access to the PBS Level 2 road network
M = 3L + 12.5 for M <= 46.5 t and M =1.5L + 29.5 for M >= 46.5 t 

Access to the PBS Level 3 and Level 4 road networks
M = 3L + 12.5 for all M 

For information pertinent to Tier 2 and Tier 3 refer to the PBS Scheme Standards and Vehicle Assessment Rules.