3.3.2 Components of a Temporary Traffic Control Zone

1. Advance Warning Area
2. Transition Area
3. Work Area
4. Termination Area

*Spacing Distance “D” – a basic system for remembering the spacing of signs and taper lengths.

*Dimension  “D” – a distance expressed in meters equal to the approach speed of traffic in kilometers per hour.

3.3.2.A Advanced Warning Area

• The advanced warning area is the section of highway where road users are informed about the upcoming work zone or incident area.
• Signs to provide warning, guidance, or instruction are provided in this area.
• Other signs in the advance warning area provide additional warning to road users or inform drivers of specific action that may be required ahead.
• The first advanced warning sign seen by drivers is generally ‘ROADWORKS AHEAD’
• First sign is located 2D meters before the works or start of taper – e.g. for 60 kph approach speed, the distance is 120 meters prior to the taper or works area.

Situation 1 (Common)

Advanced warning sign must be located at a minimum distance of 2D meters before the start of the work, or if there is a transition area, the start of the taper.

“For example, if the approach speed of traffic is 60 kph then the ‘ROADWORKS AHEAD’ sign should be a minimum of 120 meters before the taper or works area.”

Situation 2

In cases where a specific action is required from road users or drivers, additional signs may be provided  in the advance warning area. The sign closest to the work should be at a distance of 2D with other signs generally spaced D meters apart.

“If two or more signs are provided in the advance warning area, the ‘ROADWORKS AHEAD’ sign may need to be a distance of 3D or more prior to the works.  However, where visibility is good and there are more than two advanced signs, the spacing of signs may be reduced to a minimum of 0.5D.”

3.3.2.B Transition Area (Taper)

A Transition Area is where drivers are redirected out of their normal path of travel.  If a roadway needs to be partially closed the taper that guides drivers to the new travel path clear of the worksite is provided within the transition area. 

The way traffic is managed at the worksite, determines the type of taper to use.

Lateral Shift Taper shifts a line of traffic sideways when it does not need to merge with another line of traffic traveling in the same direction. This is sometimes referred to as a “diverge taper”. This should be at least “D” meters long.

For example if the approach speed of traffic is 50 kph the lateral shift taper should be 50 meters.  However, when a Traffic Controller is being used a 30 meter taper is adopted as the traffic would be approaching the taper at a slower speed. 

Merge Taper shifts a line of traffic sideways where the traffic must join with another line of traffic traveling in the same direction; should be at least 2D meters long.

For example, if traffic is traveling at a speed of 70 kph the merge taper should be 140 meters.  A merge taper requires a longer distance because drivers are required to merge into common road space.

Devices used for forming the taper may be:

• Temporary hazard markers
• Traffic cones
• Temporary bollards

The spacing for Traffic Cones or Bollards to create a taper should be 5 to 10 meters.

3.3.2.C Approach Clearance Area for Workers

Approach Clearance Area for Workers is a longitudinal safety buffer immediately in advance of the work area that increases protection and safety for workers.

• Generally, 20 to 30 meters long.  Longer if works are hidden from approaching traffic eg. by a crest or curve

• the clearance area should be kept clear of workers, vehicles, machinery

3.3.2.D Adjacent Clearance Area for Workers

Adjacent Clearance Area for Workers is a lateral safety buffer beside the work area that increases protection and safety for workers.

• Adjacent Clearance Area for Workers, minimum of 1.2 meters wide for low speed areas
• High speed areas –  a larger adjacent clearance area is desirable or consideration given to providing a roadworks speed limit. 
• High volume and very high speed locations (e.g. expressways) –  a safety barrier adjacent to the work area should be considered to provide protection and safety for workers.

3.3.2.E Work/Activity Area

Area where works are physically being carried out and is set aside for workers, machinery, equipment and storage materials.

Signs and devices to prohibit access to the Work Area

• Traffic Cones
• Temporary Bollards
• Concrete Barriers
• Water Filled Plastic Barriers
• Plastic Mesh or Tape

3.3.2.F Termination Area

Area where traffic resumes normal operations after passing the worksite. 

Signs and Devices used in the Termination Area

• Taper to allow normal flow of traffic
• END ROADWORK signs
• END DETOUR sign
• End Speed limit sign

3.3.2.G Advanced Signage Layout for low speed road (< 80kph).

3.3.2.H Advanced Signage Layout for very high approach speed road (> 80kph).