TRAFFIC CONTROL CONCEPTS FOR INCIDENT CLEARANCE
5.0 ROLE OF TRAFFIC CONTROL DEVICES AS WARNINGS FOR APPROACHING TRAFFIC
An incident scene should be considered a temporary work zone: an area of impact that must be secured and that must be balanced with the need to control traffic flow. Reducing the incident duration is also important because that will reduce the risk of secondary incidents. There are various traffic control devices available to incident responders. Guidelines for application, use, and placement can be found in Part 6 of the MUTCD. 2 Some of the devices are used during the initial traffic control as a temporary measure; others are set up with longer term traffic control in mind. Whatever their intended duration, these traffic control devices help to secure the incident scene and provide protection for incident victim, responders, and the motorists passing by the incident.
- Traffic control components at an incident, same as in standard maintenance of traffic work zones, can be broken into four major areas: 2
- Advance warning area (advance warning signs, cones, flares, or emergency vehicles)
- Transition area (strategic use of tapers)
- Activity area (channelizing devices)
- Buffer space (protected by energy absorption or attenuation devices or official vehicles)
- Work or incident area (responders)
- Termination area (strategic use of tapers)
Figure 1. Component Parts of a Temporary Traffic Control Zone 2
The traffic control setup calls for various types of devices and configurations within these zones. The following are some devices that are used either in the initial traffic control and/or for longer duration periods.
Personal Protection Equipment (PPE)
All responders, inclusive of fire-rescue personnel, emergency medical service ( EMS) crews, law enforcement, department of transportation (DOT) personnel, and tow truck operators, face inherent risks when responding to an incident. For obvious reasons, including public recognition of roles and responsibilities, conspicuity, and personal safety, Section 6D.03 of the MUTCD 2 recommends that all workers should wear bright, highly visible clothing when working in or near moving traffic. This includes fire-rescue personnel, EMS crews, DOT personnel, law enforcement, and tow truck drivers.
Federal regulation (23 CFR 634), in effect by November 24, 2008, mandates the requirement for all emergency responders working in the right-of-way of a federal-aid highway to wear high-visibility clothing that meets the requirements of American National Standards Institute (ANSI) / International Safety Equipment Association (ISEA) 107; 2004 edition class 2 or 3. 22
These new requirements stipulate entity specifics, type, minimum material coverage, color, retroreflective performance, and material dimensions and placement.
Vehicle Lights and Flares
Flashing lights (red, white, amber, blue, and / or green) on emergency vehicles are used to enhance the safety of response personnel and incident victims and are essential in the initial response stage. The National Highway Traffic Safety Administration and Federal Motor Carrier Safety Administration of the Federal DOT have the authority to establish these vehicle lighting requirements; however, the allowable light colors for emergency response vehicles are normally spelled out in individual state code.
Warning light applications are being advanced with the development of light emitting diode technology and include relatively new features, such as wig-wag, oscillating, and strobe capabilities. There are also a limited number of states, such as Texas, that allow blue auxiliary lights along with standard amber lights on DOT maintenance and freeway service vehicles used in high-risk activities. 23
Flashing lights, high–intensity rotating, flashing, oscillating, or strobe light systems, mounted outside as well as inside emergency response vehicles, provide visibility and give immediate information to the traveling public of an emergency situation. However, once at the scene, and as the traffic control is being addressed, it is recommended that only amber, rather than red color, warning lights be used and that the number of lights be minimized to avoid creating a glare for motorists and reduce “rubber necking” behavior.
There is also evidence that suggests too many warning lights can be confusing to drivers. Flashing lights should, therefore, be used with discipline and discretion to minimize the impact on traffic flow. Their use should be reduced once good traffic control is established at the incident scene with particular attention to forward-facing emergency lighting, especially on divided highways.
In addition to using emergency vehicle placement as an initial traffic control setup, the responders should carry enough emergency flares that can be used to set up a temporary lane closure taper until other efforts, such as traffic cones, can be placed. Flares are especially useful in night time incidents to warn motorists of lane changes as the bright red lights of the flares tend to visually merge. They also can be used to supplement the visibility of traffic cone placement under night conditions. When the flares are placed near the cones, they not only warn up stream traffic, but the light also illuminates the cones. 24
Arrow boards are additional advance warning traffic control devices used where a lane(s) is closed and traffic must merge with other traffic in an adjacent lane. The effective placement of arrow boards is contingent on sight visibility; attention must be paid to the road geometry and speed of the roadway when determining placement. For multiple lane closures, the arrow board should be placed at the beginning of the taper. Figure 2, taken from the MUTCD, shows the various panel displays that are acceptable. However, there are restrictions on the use of an arrow board on a two-lane, two-way highway; only the “Caution” display should be used for this type of facility. 2
Figure 2. Arrow Board Displays 2
While trailer mounted arrow boards are required for certain work zone traffic control setups applicable to intermediate and long term incident traffic control, the immediate availability of the boards and transport to the scene of an incident can be a logistical issue. Some DOTs are now mounting arrow boards on their maintenance or other work vehicles, not only for use in routine maintenance activities, but also to have immediately available for emergency response. These vehicle mounted boards can be used to provide supplemental displays to support traffic control. Some of the devices have the capacity not only to display the arrows, but also text and other symbol messages. It is important that the responders receive training in the actual operational requirements of the arrow board as well as in the development of appropriate message sets to fully utilize the available board functions at the incident scene.
Figure 3. Traffic Control Example of the Use of a Truck Mounted Arrow Board 25
Changeable Message Signs
Changeable message signs (CMS), either portable or those placed permanently at critical major decision points of the road system, can be used to provide notice and information, such as lane changes and available alternate routes as well as to alert motorists to detour or expect delays in advance of the incident. The earlier the information can be provided, the greater the opportunity to reduce traffic demand at and approaching the scene as well as reduce motorist frustration. Because these signs are a powerful communication means with motorists, information should be as real-time as possible. The portable trailer mounted CMS can be procured with remote communication capabilities, such as cell phone, radio, or internet; the permanent signs are normally operated via a traffic management center. While the CMS text capability is limited as to the amount of information provided, this form of communication is very effective. Information relayed can include:
- Specific incident location
- Expected incident duration
- Alternate route details
- Diversion directions, including non-standard motorist actions (such as temporarily driving on the shoulder) 2
States such as Minnesota have developed and published guidelines to assist determining the appropriate use as well as appropriate and consistent incident management message development.26
Heavy trucks or trailers, often with rear-mounted energy adsorption attenuation equipment, become a traffic control device when parked to protect a work zone or incident area. It should be placed with the traffic 100 to 250 feet up-stream from the incident work space with the wheels cut toward the shoulder. It should not be occupied by anyone as its purpose is to protect the work area by taking any hit before an errant vehicle can enter the zone where people may be otherwise unprotected. 24
Initially, manual traffic control may have to be provided by qualified trained personnel during the initial phase of the response; this is normally the responsibility of the responding law enforcement personnel, but could also be other emergency responders, such as DOT or freeway service patrols, fire or tow operators. Flagmen may be used to guide traffic when:
- Travel lanes are partially blocked,
- Shoulder must be used to pass by the incident, or
- Only one direction of traffic is available.
It is important that the flag person knows to always face traffic and direct the traffic away from and safely around the incident, using large, extended, and consistent gestures to convey the required actions to drivers. 2
Figure 4: Flagging Methods 2
These responders should be properly trained. While some agencies, such as DOTs, offer their own flagger training and certification program, the most common commercially available programs are offered through the American Traffic Safety Services (ATSSA) and the National Safety Council. ATSSA also offers training specifically for law enforcement personnel.
A resource for additional information on individual state requirements and available courses and programs is the National Work Zone Clearing House Web site available at http://www.workzonesafety.org/training/flagger_training. 27
The Towing and Recovery Association of America also offers a three level National Driver Certification for tow truck operators, which includes incident management training. 28
First responders such as DOT personnel, law enforcement, and fire-rescue, may also carry flexible, roll-up signs with specific incident messages that can be set up quickly using portable light weight spring stands at an incident site. The color of fluorescent pink has been designated as an option to orange by the MUTCD as the color to indicate an emergency incident. However, there are some jurisdictions, such as the state of Minnesota, that continue to use orange colored signs and have not adopted the fluorescent pink signs. 29 At locations where there are historically recurring incidents, there may be consideration to permanently mount this type of roadside signage that only has to be uncovered during the time of an incident. The signs for incident management may be of the mesh or fabric type. Chapter 6I of the MUTCD 2 has details on specific roll-up sign designs for incidents. They have a black legend and are on a fluorescent pink background. Incident responders can carry these signs in their vehicles and have them available during the initial traffic control setup. Cones, barricades, and other devices are supported by signs when informing motorists of actions needed to merge or otherwise adjust for lane tapers and closures.
Figure 5: Incident Management Signs 2
Highway Advisory Radio
Highway advisory radio (HAR) may be a portable AM unit brought out to the incident scene or a permanent roadside installation that can be used to disseminate incident information in advance of an incident so that motorists can adjust their travel choices and avoid any traffic queue resulting from the incident. Remote communication links to the HAR allow the operators the ability to activate and modify the broadcast messages as required for the incident. Like the CMS, HAR is most effective for motorists who are still at least one interchange or other decision point away from the scene of the incident. The earlier information can be provided, the greater the opportunity to reduce traffic demand at and approaching the scene as well as reduce motorist frustration. HAR message content is similar to that shown on CMS, except it can be provided in much greater detail. HAR cannot, however, always be relied upon because not all motorists will tune in to the emergency broadcasts. There are also issues regarding the range and quality of broadcast because of a variety of interference factors.
Traffic Cones and Barridcades
Traffic cones and barricades are used to set up lane closures and their associated tapers to control traffic moving past the incident scene. 2 Incident responders may be able to carry a limited amount of cones or barricades; however, the “standard” amount needed for regulation tapers and closures usually arrives when transportation agency personnel arrive on-scene to support with longer-term lane closures. The “standard” length of taper and placement of the cones and barricades are dictated by the offset (or width of the required shift of the traffic lane) and speed of the facility as prescribed in normal work zone directives. Such a set up is normally required if, in the judgment of the ICS team commander, the estimate of the affect on the travel lanes will exceed a 30 minute time frame.
Cones may be carried as standard equipment by first responders. Since limited storage is a consideration, one solution to carrying this device is to use the “collapsible” cones, cones that can be compressed for storage and “pop up” to the correct height when needed. 24
Emergency vehicles may be parked in such a way as to protect incident responders and secure the scene before more permanent traffic control devices arrive. However, the vehicles should be placed in a way that minimizes their impact on traffic flow. Preferably all emergency vehicles should be parked on the same side of the roadway, in the same direction of the incident. For example, law enforcement and fire-rescue vehicles can be parked to provide some security for the incident scene; however, if they unnecessarily block lanes, they will cause significant disruption to traffic flow and lengthen the time needed to restore normal traffic flow. As soon as these vehicles complete their response function, the incident commander can require their relocation out of the travel lanes
North Carolina DOT has developed a convenient Emergency Responder Reference Card 30 which provides a quick reference to how and where emergency vehicles should be parked at the scene. Tools such as these are extremely helpful as a reminder especially for new first responders or when there is confusion in the field.