Traffic Control Guideline #1

Traffic Control Person Positioning

The position chosen for the Traffic Control Person (TCP) is critical to both his/her ability to control traffic and personal safety. A number of factors need to be considered when determining the best location. They include:

Location In Relation To Site Hazards

When deciding on a position for both the TCP and the traffic queue, site hazards must be identified and assessed to determine if they pose a risk. TCPs and traffic queues should never be positioned where they are at high risk from a site hazard without taking appropriate steps to eliminate or minimize the risk. Remember: TCPs must be able to focus their attention on traffic and must not be distracted by having to "watch out" for another hazard.

Site hazards may include:

• rock fall areas or avalanche zones (seasonal)
• blind corners, hill crests, or entrances and exits of tunnels
• lengthy or steep grades
• danger trees
• dark or remote areas
• heavy congestion or commercial areas
• wildlife

Spacing Between TCP and Traffic Control Person Ahead Sign

Appropriate spacing between the Traffic Control Person Ahead (C-28) sign and the TCP is essential to ensure motorists receive enough warning to allow them to slow and prepare to stop. However, too much space reduces the effectiveness of these advanced warning signs. Field studies have demonstrated that the further away this sign is from the appropriate position, the less effective it becomes.

Too Close:

If not enough space is left between the advanced warning sign and the TCP, motorists will not have enough time to react to the sign (decision sight distance). The spacing outlined in the Traffic Control Manual for Work on Roadways factors in this need.

• Example: The average vehicle traveling at 90km/h on flat, dry ground requires a minimum of 168 metres to stop. If you only leave 120 metres, the vehicle may not be able to stop on time.

Too Far:

All signs should be no closer than the distance specified in the manual and no further than 15-20 seconds away – with special attention to the C-28.

Studies have shown that motorists will react positively to signing and alter their driving pattern for approximately 15 seconds. If in this time they do not see additional signing or supporting evidence for continuing with the "altered driving pattern", they will gradually resume their previous pattern of driving.

This resumption of the previous driving pattern may be due to motorists questioning the validity of the sign, assuming it has been accidentally left up, assuming they have passed the work area without noticing it, or simply forgetting what they were directed.

Note:  The suggested layout in the Traffic Control Manual for Work on Roadways allows for the spacing between the TCP and the C-28 to be in excess of 1.5 km. In this case, the TCP must ensure that motorists have enough decision sight distance according to the posted speed and driving conditions.

Line of Sight for Approaching Vehicles

It is imperative that both motorists and TCPs are able to see each other with enough time to react.

The reaction time of the motorist is dependent on the speed, road conditions, amount of deviation from the normal pattern of traffic and driver’s ability. The distances in the Traffic Control Manual for Work on Roadways are based on research that balances reaction time with effectiveness under optimum driving conditions. These distances may need to be adjusted due to weather conditions or site impediments (such as blind corners or crests, shoulder obstacles, etc.). However, distances should not differ significantly without being thoroughly assessed to ensure they are appropriate and are the best method available.

• Example: Due to a winding road the TCP may want to increase the sign spacing to provide more room for the traffic queue. However, when the queue is short the spacing is too long. A remedy to this may be to add another sign to the set up or double up a sign.

Note: The C-28 should never be doubled up and no other signing should come between the sign and the TCP. We want motorist’s sole focus on locating the TCP.

Competition for Motorists' Attention

From a motorist’s perspective, there are many things competing for their attention while driving through a work zone. The TCP and other devices may not always be the biggest "attention grabber".

Therefore, when deciding on a position for both TCPs and traffic devices, assess the area to determine if there are other things that will distract motorists. Billboards, equipment, vehicles, work activities, and changeable message boards tend to overshadow standard signs and TCPs, if located in the same area.

Also, positioning TCPs in the immediate area of other workers wearing hi-viz. vests is distracting for motorists and makes identifying the TCP difficult. TCPs and signing should be set apart from competitors. This may require moving TCPs away from the immediate work area. Communication may need to be achieved through radio usage or hand signals. The need for communication should not be used as an excuse to position workers in a poor location.

Ability To Make Evasive Maneuvers

TCPs must be located in a position that will permit them to make evasive maneuvers required to avoid being struck by a vehicle. Although many TCPs use their vehicles as refuge, they should not be positioned in such a way that the presence of their vehicle or other equipment reduces the options for evasive maneuvers. The same principle applies to working near equipment, other physical barriers, or opposing traffic.

For the most part, TCPs should:

• be positioned in the shoulder of the road or in the closed lane when stopping traffic.
• ensure their sole focus is on the vehicles they are directing.

TCPs should not:

• stand in the traveled portion of roadway, even after the first vehicle is stopped; an accident at the end of the queue could force the first car forward and strike the TCP.
• stand in the path of the vehicle or on the traveled portion of roadway with their back to the vehicles they are directing; if they don’t see the vehicle coming, they cannot move out of the way.

Shanna Mason
Ministry of Transportation
Thompson-Okanagan / Kootenay Regions

November 2000