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How NZGTTM Uses Risk Instead of Fixed A, B and C Site Categories

TM Matters Team2026-04-108 min readIndustry Guide
NZGTTM categoriesCategory A B C NZtraffic management categories NZNZGTTM explainedwhat is Category A traffic managementCategory C traffic management NZ

NZGTTM uses a risk-based approach and does not create universal Category A, B and C site classes. Those labels may still appear in older CoPTTM records, training histories or contracts during transition, but current planning should start with the actual work, road environment, road users and risks.

How should older A, B and C references be read?

Treat an older category label as background information, not as the final risk decision. The PCBU, designer and site team still need to establish the required functions, competency, controls and review pathway for the specific job and the relevant road controlling authority.

Older Category A references

What to check when Category A appears

Older Category A terminology often described lower-speed or less complex local-road work. Do not rely on the label alone. Check:

  • The actual operating speed and road geometry
  • Current traffic demand and peak-period conditions
  • The real work footprint and available recovery space
  • Sight distance, intersections and property access
  • Impacts on pedestrians, cyclists and public transport

Examples that still need site-specific assessment

  • Residential vehicle-crossing or driveway work
  • Short-duration utility connections
  • Footpath maintenance and pedestrian detours
  • Vegetation work near live traffic
  • Sign installation and mobile activities
  • Property-access changes

Planning requirements are site-specific

Even apparently simple work needs controls that fit the actual site. Consider:

  • A clear site-specific layout and work method
  • Signs and devices selected for the identified risks
  • Work space, safety space and escape considerations
  • Advance warning appropriate to speed, visibility and approach conditions

Competency for the assigned function

A historic warrant or course is not, by itself, authority to manage every site. The PCBU should confirm that the person can:

  • Understand the work activity and road-user risks
  • Read and implement the approved TMP
  • Work within the limits of their demonstrated competency
  • Recognise when conditions require review or escalation

Keep competency evidence current through appropriate training, assessment, supervision and work records.

Older Category B references

What to check when Category B appears

Older Category B terminology often described more complex local-road environments. Current assessment should consider:

  • Operating speed, geometry and available sight distance
  • Traffic demand, heavy vehicles and peak conditions
  • Lane, shoulder, parking and access impacts
  • Intersections, multiple lanes and network effects
  • Night, weather and visibility risks
  • Schools, bus stops and vulnerable road users

Examples requiring closer risk review

  • Commercial construction affecting the corridor
  • Road resurfacing and maintenance
  • Utility work on arterial roads
  • Multi-day or staged maintenance
  • Lane closures on busy roads
  • Projects changing pedestrian or cycle routes

Planning for added complexity

More complex sites may require:

  • Staged layouts tied to the construction method
  • Device schedules and placement appropriate to each stage
  • Safe, accessible pedestrian and cyclist routes
  • A justified speed-management approach
  • Property, work vehicle and emergency access planning
  • Advance warning and contingency measures

Competency for more complex work

Where a contract still uses Category B wording, confirm the current credential and competency expectations. Relevant evidence may include:

  • Training relevant to the assigned function
  • Recent experience in comparable road environments
  • Employer or PCBU assessment and authorisation
  • Recognise when conditions require review or escalation

Review competency whenever the function, work environment or risk changes, and check any RCA, principal or contract requirements.

Older Category C references

What to check when Category C appears

Older Category C terminology often described high-speed or complex network environments. Current assessment should examine:

  • Higher-speed approaches and safe stopping distance
  • High traffic demand and network resilience
  • Restricted work space and limited recovery options
  • State highway, motorway or major arterial interfaces
  • Detours, portable signals and specialist equipment
  • Multi-stage work and changing access requirements

Examples requiring specialist planning

  • State highway construction or maintenance
  • Major road reconstruction
  • Bridge work and constrained work zones
  • Large utility work on busy corridors
  • Projects using portable traffic signals
  • Work with material network-wide effects

Planning for high-consequence risks

High-consequence sites may require:

  • Traffic analysis proportionate to the network impact
  • Detailed staging and hold-point decisions
  • Detour design and stakeholder coordination
  • Specialist signal or equipment planning
  • A documented, site-specific risk assessment
  • Coordination with affected parties and asset owners
  • Contingency and network recovery planning

Competency for complex environments

Do not assign a person to a complex environment solely because an older record says Category C. Confirm:

  • Training or credentials relevant to the function
  • Recent evidence from comparable complex work
  • Specialist, engineering or operational support required
  • Recognise when conditions require review or escalation

The PCBU should record why the person is competent for the assigned work and how that competency will remain current.

The practical difference under NZGTTM

There is no universal NZGTTM table that converts speed, traffic volume or an old A, B or C label into an automatic site class, TMP complexity or permission to act. Make a site-specific risk decision and confirm the applicable RCA, principal and contract requirements.

How to determine the right planning pathway

Start with the exact location, work method, dates, road users, operating environment, access effects and hazards. Then confirm the RCA, principal and contract pathway. A competent TMP designer can help turn that information into a site-specific risk assessment and plan.

TM Matters can review the available project information and explain the likely TMP, CAR/WAP and planning inputs before a scope is agreed.

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