1. Compliance Framework

Portable traffic signals used in New Zealand must:

• Comply with AS 4191:1994 – Portable Traffic Signal Systems
• Be listed on the NZTA register of approved systems
• Be authorised through an RCA‑approved Traffic Management Plan (TMP)
• Operate in accordance with NZGTTM risk‑based principles

Only systems meeting these requirements may be used on public roads.

2. Signal Head Requirements

Standard Aspects

• Three‑aspect arrangement: Red / Yellow / Green
• Circular lenses only (arrows require specific approval)
• No flashing red or green indications (except fail‑safe yellow)

Lens Size

• 200 mm diameter lenses (industry standard)
• Must meet visibility distance requirements for the speed environment

Height

• Minimum: 1.0 m to the bottom of the lowest lens
• Typical: 1.5–2.2 m to the centre of the red aspect
• Must remain visible above vehicles, cones, and plant

Backing Board

• Black, matte, high‑contrast backing board
• Sized to provide a clear silhouette around the lenses
• Reduces sun‑washout and improves daytime visibility

Visibility & Brightness

• Must be visible in full daylight and at night
• Automatic or manual brightness control
• No ghosting or false indications
• Must be visible from the required stopping distance (typically 60–100 m)

3. Placement Requirements

Orientation

• Signal head must face squarely down the lane
• Must not conflict with permanent signals (bag, cover, or isolate if required)

Stop Position

• A defined stop point is mandatory
• If no painted stop line exists, a STOP HERE ON RED sign must be used
• Signal must be clearly visible from the stop position

Spacing

• Adequate sight distance between the warning sign and the signal
• Correct separation between opposing signals in shuttle mode
• Ensure no obstructions (plant, barriers, vehicles)

4. Required Signage

Advance Warning Sign (choose one)

One of the following must be installed before the signalised control:

• TRAFFIC SIGNALS AHEAD (TW‑15)
• PORTABLE TRAFFIC SIGNALS AHEAD (TW‑15.1)

Stop‑Line Sign (mandatory)

• STOP HERE ON RED (R1‑2)
• Defines the legal stop position
• Required where no painted stop line exists

Not required

• STOP ON RED SIGNAL (R1‑1) – intended for permanent intersections only

5. Operational Requirements

Communication

• Reliable communication between signal units (radio, cable, or approved wireless)
• Loss of communication must trigger a safe shutdown

Power

• Battery, solar, or hybrid systems permitted
• Must maintain continuous operation for the duration of the worksite
• Power levels must be checked as part of daily inspections

Fail‑Safe Behaviour

If the system detects:

• Communication loss
• Lamp failure
• Power failure
• Internal fault

It must default to:

• Flashing yellow, or
• All‑off with manual STOP/GO control

This is a strict AS 4191 requirement.

6. Daily Inspection Checklist

• Signal heads clean, visible, and correctly aligned
• Backing boards fitted and unobstructed
• Warning sign installed at correct distance
• STOP HERE ON RED sign in place
• Communication link confirmed
• Batteries/solar charging verified
• Fail‑safe tested
• Permanent signals bagged or isolated
• No obstructions to sight lines

7. Summary

Portable traffic signals provide a safe, controlled method for managing temporary traffic flows. Compliance with AS 4191, NZTA approval, and NZGTTM ensures:

• Clear driver expectations
• Reliable operation
• Defined stop positions
• Safe fallback behaviour
• Consistent national practice