Traffic Control Tools
Traffic control tools range from the traditional tools such as signs and traffic signals to ITS tools as discussed earlier in this primer. Where available, both types of traffic control tools should be used. Since ITS has already been discussed, this section focuses on the more traditional means of controlling traffic and how they might be used in an evacuation. A complete listing of traffic control devices applicable to incident and emergency management may be found in the Manual on Uniform Traffic Control Devices (MUTCD). A link to the MUTCD is included in the “Other Information Resources” section of this primer.
TIM Assets—Many States and localities have TIM programs. TIM allows for collaboration across government and the private sector, including between transportation and public safety, to ensure that response to incidents is quick to minimize disruptions to the flow of traffic. Good TIM during an evacuation is especially important as even a minor accident could delay the clearance of an area by several hours. Personnel and assets assigned to TIM programs such as motorist assistance teams may form the base of an EOT or provide operational support to an EOT during an evacuation. TIM personnel are usually trained in ICS.
Traffic Counting Devices—Most State and local transportation agencies have a routine traffic counting program that enables them to record the number of vehicles, types of vehicles, travel direction of vehicles, and the time of day of vehicle travel. Personnel in the field may do these counts manually, by portable counting tubes placed across the roadway, or by permanent sensors placed in the roadway pavement. The value of this data in an evacuation is providing information about the progress of the evacuation, the number of vehicles evacuating and their destination, so that those executing the evacuation and those receiving the evacuees can be better prepared.
Traffic Signals—Traffic signals at intersections may be stand-alone devices or interconnected through a computerized signal system. When computerized, the timing of the traffic signal cycles can be easily modified for an evacuation, changing the signal timing to give longer “green time” in the direction of the evacuation and on evacuation routes assisting in moving more vehicles in a shorter amount of time. The signal timing must take into account other travel needs such as the ingress of emergency vehicles and equipment. Some traffic signals may be placed in “flash mode” to allow more through travel or may be operated manually by a law enforcement officer at an intersection. Traffic signal timing adjustments may also be needed to support re-entry operations. Some communities have installed an uninterruptible power supply (UPS) on their traffic signal system or have equipped key intersections with generators to ensure the traffic signals continue to operate if power is lost in the area.
Traffic Signal Timing Plans—Many locations plan in advance for the modification of their traffic signal timing for an evacuation. This allows signal timing to be changed quickly and law enforcement to know what to expect in terms of changing traffic patterns. Signal timings are often developed in advance for detour routes that may also be needed in the event of an emergency. This information should be incorporated into evacuation plans and SOPs.
Traffic Signal Pre-emption—Some locations have installed pre-emption devices on some traffic signals. These pre-emption devices allow an approaching emergency vehicle to change the traffic signal timing pattern to allow them to proceed unimpeded through the intersection.
Ramp Meters—Some locations have ramp meters, which are traffic signals on freeway entrance ramps that stop traffic at certain intervals to allow for the timed entry of vehicles on the ramp into the main flow of traffic.
Ramp Gates—A few locations have installed gates at freeway entrance and exit ramps that can be used to prevent traffic from entering and exiting the freeway at certain locations. These may be especially useful if contraflow is being used for an evacuation.
Traffic Signs—All highways have some form of traffic control signs to control speed and provide other regulatory information. Signs are also used to provide information to motorists. In an evacuation, these signs may be used to designate an evacuation route or show the location of shelters, or perhaps contraflow traffic patterns. In some locations, flip down signs have been installed that can be flipped down to provide emergency information and flipped up when an evacuation is not underway. Some locations have installed signs on the back of other traffic signs that can only be seen during contraflow operations.
Pavement Markings—All highways have some type of pavement markings to designate travel lanes, emergency lanes, High Occupancy Vehicle (HOV) lanes, merge locations, etc. Some locations use pavement markings to show that the road is an evacuation route or that emergency lanes can be used as travel lanes in an evacuation, or have mileage markers or exit numbers allowing those doing aerial monitoring of an evacuation to pinpoint specific locations.
HOV Lanes—Some cities have designated HOV lanes that are usually used to speed rush-hour traffic for those willing to share the ride. In emergencies, some locations use the HOV lanes as an extra lane for evacuation or as an ingress lane for emergency vehicles and supplies.
Frontage Roads—Some cities have frontage roads along limited or controlled access roadways. These frontage roads can provide a means to circulate emergency vehicles during an evacuation.
Reversible Lanes—In some locations, highways and bridges have been built with reversible lanes both on freeways and arterials. These lanes can be modified to switch the direction of travel during peak hours to accommodate rush-hour traffic. Reversible lanes could also be employed in an evacuation as necessary.
TMCs—The mission of TMCs is to facilitate the safe movement of people and goods, with minimal delay, throughout the roadway system. TMCs achieve their mission by: (a) maximizing the available capacity of the area-wide roadway system; (b) minimizing the impact of roadway incidents (accidents, stalled vehicles, and debris); (c) contributing to the regulation of demand; (d) assisting in the provision of emergency services; and (e) creating and maintaining public confidence in the TMC.