3.3. Worksite Layout of Signages and Devices

Temporary Traffic Control Zone (TTCZ) – area of a highway where road user conditions are changed because of a work zone or incident by the use of temporary traffic control devices, flaggers, uniformed law enforcement officers, or other authorized personnel.

Functions of a Temporary Traffic Control

• To provide for the reasonably safe and effective movement of road users through or around TTC zones while reasonably protecting road users, workers, responders to traffic incidents, and equipment.
• To provide for the efficient completion of whatever activity that interrupted the normal use of the roadway.

3.3.1.  Temporary Traffic Control (TTC) Zone

No one set of TTC devices can satisfy all conditions for a given project or incident.  At the same time, defining details that would be adequate to cover all applications is not practical. The TTC selected for each situation depends on the following:

• type of highway,
• road user conditions,
• duration of operation,
• physical constraints, and the
• nearness of the work space or incident management activity to road users.

Roadwork Traffic Management Guide:

• The principles of worksite traffic management mentioned should still be applied with consideration given to the following: 
• Sign locations and spacing may need adjustment to suit road alignment, visibility, traffic speeds etc.
• Lane tapers using cones, bollards or temporary hazard markers should be gradual and reinforced with appropriate signs
• All layouts should be driven at the expected traffic speed and adjustments made if necessary. 

Components of a Temporary Traffic Control Zone

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

Definition of Terms

• 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.  Advance Warning Area

• The advance 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)

Advance warning sign must be located at a minimum distance of 2D meters before the start of the works, 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.

3.3.3.  Transition Area (Taper)

• the area 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 that you have chosen to manage the traffic at then worksite, will determine you the type of taper you should 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 sometimes referred to as a “diverge taper”. 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.