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Public Roads - March/April 2014

March/April 2014
Issue No:
Vol. 77 No. 5
Publication Number:
Table of Contents

Creating Smarter Work Zones

by Tracy Scriba and Jennifer Atkinson

Advances in high-tech tools mean improved safety and efficiency during roadwork.


The Texas Department of Transportation deployed this portable message sign as part of an end-of-queue warning system used during a construction project on I–35. This system is one of many technologies that State and local highway agencies can use to improve safety and mobility in work zones.


Have you ever approached a work zone on a highway and found yourself in a backup that made you late for an appointment? Or driven through a work zone at night and found it challenging to navigate? Or traveled through a construction area wondering how workers stay focused with traffic driving right by their “offices?” If you drive regularly, you have likely experienced one or more of these scenarios and perhaps considered the impact that work zones have on congestion and safety.

These areas are estimated to cause 10 percent of all congestion and 21 percent of the less predictable kind of congestion that varies from day to day and makes travel times for trips unreliable. Significant congestion in urban areas can result from closing lanes during the day for roadwork, which may cause unacceptable delays to road users and businesses. This issue has led some local jurisdictions to enact policies to specify that all work on major roads must be done at night.

The conflict exists because traffic and roadwork are using the same space. A large portion of highway construction is repairing and improving existing roads. In 2008, 80.5 percent of highway capital expenditures were allocated to system rehabilitation (51.1 percent), expansion of existing roads (17.4 percent), and enhancement (12 percent) of those roads. For system rehabilitation, that amounts to about $40.4 billion.

Safety implications result from traffic and roadwork occurring in such close proximity. In 2010, more than 87,600 crashes occurred in work zones, resulting in 576 deaths and almost 26,300 injuries. More than 20,000 workers are injured in work zones each year, with 12 percent of those due to traffic incidents. Challenges to work zone safety and mobility are also exacerbated by the growing issue of distracted driving.

Roadway work zones are necessary to maintain the transportation network for mobility, safety, and productivity, so eliminating roadwork is not an option. However, various technological tools are available to help transportation professionals effectively plan for, implement, and manage work zones on all types of roadways. Technological advances in work zone safety and efficiency, in combination with other strategies, help to address specific needs while keeping workers and the traveling public safer.

Technological Solutions

The transportation community can use technology to identify and assist in remediating work zone issues. Technologies can detect and help mitigate queues, manage speeds, reduce worker exposure, gather performance data, identify and facilitate responding to incidents quickly, inform road users of traffic conditions, improve the visibility of traffic controls in work zones, improve road user and worker safety, and inform future work zone strategies.

The use of technology, including intelligent transportation systems (ITS), in work zones is one of many possible strategies that agencies can incorporate into their transportation management plans (TMPs). A TMP, as required by the Federal Work Zone Safety and Mobility Rule, lays out a set of strategies for work zone management--traffic control, public information and outreach, and transportation operations--that an agency will use to manage the impacts of a particular road project. Considering whether to deploy technology/ITS on a project and designing and deploying a system should be done as part of the impacts assessment for a work zone and the development and implementation of a TMP.


ITS applications for use in work zones, such as this smartphone app that shows realtime messages on roadway signage, can help motorists plan ahead and make more informed decisions prior to trips.


“The success stories of technology use to mitigate work zone impacts continue to mount nationally, to the point that the traveling public is now beginning to expect and even demand it,” says Gerald Ullman, senior research engineer at the Texas A&M Transportation Institute. “I believe that those agencies and contractors who learn how to best incorporate work zone technology into their decisionmaking processes and ways of doing business will be the most successful and profitable in the future.”

History and Evolution

Technology has made work zones safer, more efficient, and “smarter.” Historically, logging work zone data meant using a clipboard while watching queues onsite. Now, agencies use transportation management centers to monitor traffic; ITS to collect data and identify issues such as queues; and other technologies to relay information to motorists, manage speeds, and perform basic work zone duties.

Technological solutions once were limited to a single purpose and operated independently. For example, speed feedback signs detected the speeds of approaching vehicles and displayed those speeds to encourage motorists to slow down. Agencies did not collect this data or feed it into a larger system to monitor work zone operations or assess performance. Although speed feedback signs are still a useful, low-cost solution in some work zones, agencies now can integrate solutions over multiple platforms to analyze data and provide travelers and work zone practitioners with the knowledge they need to make informed decisions.

Another significant change when using technology in work zones is the availability of data collected by vendors. Agencies increasingly have the option to lease or purchase traffic data from companies that collect it via Bluetooth® and other technologies. This option enables agencies to leverage the technology already deployed by others and obtain useful information and capabilities without having to deploy and maintain their own sets of devices. For example, the Ohio Department of Transportation (ODOT) purchases historic and realtime speed data to monitor traffic flow, including that in work zones. One way ODOT uses the data is to plot travel speeds in work zones against historic travel speeds to identify significant delay issues to further explore in the field. “Use of this data vastly expands ODOT’s ability to monitor its work zones in a cost-effective manner,” says Dave Holstein, administrator of ODOT’s Office of Traffic Operations. “We can quickly identify issues and take steps to address them.”

Technology in work zones has typically included applying ITS solutions to create “smart work zones” or “smartzones.” Smart work zones are defined as those that use ITS to manage work zone traffic and operations. Agencies use sensors, communications, software, and electronic equipment to collect and analyze traffic flow and road conditions in real time and to provide updated, accurate information and guidance to drivers. The primary goal of a smart work zone is to improve mobility while enhancing safety for both motorists and highway workers.

Traditionally, ITS technologies were a means to provide accurate, realtime information to road users so they could make informed choices. Drivers who are knowledgeable about hazards, delays, and what actions they should take improve the safety of a work zone and reduce congestion. Today, agencies have additional uses for technology in work zones. For example, an agency can use technology to provide data for performance management and to automate some aspects of the setup of traffic controls, reducing or even eliminating the amount of time that workers are exposed to traffic.

Several common themes related to work zone issues--managing speeds and queues, reducing exposure, preventing incidents, gathering performance data and managing traffic, identifying incidents, managing traffic at nighttime, and providing traveler information--are benefitting from recent advances in technology. These advancements will help inform future work zone strategies and provide technologies that can be refined for future use.


Work Zone Technologies

Technology Description Work Zone Issue Addressed Potential Benefits and Outcomes
Managing Speeds
Automated Speed Enforcement Mobile units used in automated speed enforcement record when a vehicle’s speed exceeds a specified maximum and document the date and time of the violation. The mobile units are equipped with onboard cameras that capture images of the vehicle’s license plate and possibly the driver.
  • Crashes associated with speed and involving road workers
  • Speeding in work zones
  • Speed differentials
  • May significantly reduce fatal and severe crashes
  • Increases speed limit compliance and may reduce average speeds
Speed Feedback Signs Speed feedback signs inform approaching drivers of their current speeds and encourage them to slow down if they are traveling above the speed limit. The signs typically are portable and can be installed upstream of the work zone or within the work area when driver speed compliance is an issue.
  • Speeding in work zones
  • Can be moved to new locations as needed
  • Require minimal maintenance
  • Encourage drivers to comply with the posted speed limit
Reducing Exposure
Automated System to Install Raised Pavement Markers Automated placement of raised pavement markers reduces the need for personnel and vehicles for manual installation, while minimizing exposure to workers. A typical placement operation includes four vehicles and a six-person crew, but the Georgia Department of Transportation’s automated system requires one vehicle and only two staffers.
  • Worker exposure during installation of pavement markers
  • Reduces worker and road user exposure and increases safety
  • Reduces the need for multiple fleet vehicles to a single-vehicle operation
  • Lessens the wear and tear on vehicles associated with stop-and-go operations
  • Improves the installation rate versus traditional methods
Automated Cone Deployment System An automated machine for deployment places and retrieves traffic cones during roadway lane closures. This system can be operated by a single worker to open and close busy lanes for construction or maintenance work zones.
  • Worker exposure during setup and removal of traffic cones
  • Reduces worker and road user exposure
  • Can be operated by a single worker
Moveable and Mobile Barriers This technology allows quick barrier adjustments to create protected work spaces or to reallocate travel lanes in a work zone to match fluctuations in traffic flow. Unlike traditional barriers, which are difficult and time consuming to reposition, movable and mobile barriers are designed to be quickly moved as a unit.
  • Worker safety, particularly on highways with high speeds
  • Number, duration, and impact of needed lane closures
  • Can be moved to accommodate peak traffic flow
  • Provide positive protection in situations where a barrier might not otherwise be used
  • Can improve worker safety and efficiency
Remotely Operated Lane Closure System Installing temporary traffic control devices requires significant resources. And, as a work area changes, the locations of the temporary traffic control devices must also change, which requires personnel to enter the active roadway. A lane closure system that is remotely operated can reduce the interruption to traffic by deploying the temporary traffic control devices needed for lane closures one time and by modifying the setup from a remote location.
  • Workers in close proximity to traffic
  • Worker and traffic exposure as vehicle fleets set up signing packages
  • Impact on traffic flows associated with the installation and removal of signing
  • Can be easily installed and relocated
  • Is operated remotely
  • Uses solar power
  • Decreases the downtime associated with multiple installations of signing, which may increase the time available for construction
Work Space Intrusion Warning A work space intrusion system alerts workers when a vehicle has entered the area closed for roadwork. The system also alerts the driver.
  • Vehicles inadvertently entering the work area
  • Reduces the potential for vehicle collisions with construction equipment
  • Increases construction worker safety
Automated Flagger Assistance Device Automated flagger assistance devices are mechanically operated devices that function under the same operational principles as traditional flagging. Crews can operate the devices from a distance, which removes human flaggers from close proximity to traffic.
  • Flaggers being exposed to traffic hazards
  • Increases the safety of flaggers by removing them from the traffic lane or shoulder
Monitoring Performance and Management
Portable Traffic Monitoring Devices These devices use radar, cellular, microwave, and satellite technologies to monitor traffic conditions without a large investment of infrastructure or staff resources. The devices can detect queues and measure the average travel speed in key areas, such as in advance of and within work zone transition areas. They also store data for analysis purposes.
  • Traffic condition data in work zones to monitor and assess performance, provide traveler information, and manage traffic
  • Maximize resources by enabling easy relocation when areas experiencing issues change
  • Support policy decisions
  • Have data warehousing capabilities
  • Can facilitate data collection in locations where permanent collection devices are disabled or not feasible
Identifying and Preventing Incidents
Notification of Construction Equipment Entering and Exiting the Traffic Stream Detection technologies help to identify construction equipment entering or exiting the work area and notify motorists by changing message signage to provide an alert.
  • Vehicle collisions with construction equipment entering or exiting the traffic stream
  • Vehicles inadvertently following construction equipment into the work area
  • Reduces vehicle collisions with construction equipment
  • Increases safety of construction workers
Identifying Traffic Incidents Through Traffic Monitoring and Invehicle GPS An agency can detect when incidents have occurred by monitoring travel speeds or ITS camera images. Technologies that are primarily GPS-based and located within vehicles, such as airbag activation detection, motion sensors, navigation/GPS receivers, and other in-car control devices, provide sufficient information for identifying general traffic patterns. Such realtime information may be able to infer the occurrence of a crash. These capabilities will increase as connected vehicle technology becomes more widely deployed.
  • Delayed incident detection leading to congestion, queuing, and secondary incidents
  • May improve emergency detection and response times to the incident location
  • May enable more appropriate response equipment to be sent because of camera images
  • Reduces the likelihood of secondary crashes
  • Improves travel times through work zones
  • May be able to provide immediate incident notification through automated alerts
Managing Traffic
Use of Sequential Warning Lights to Improve Recognition of Nighttime Traffic Control Nighttime lane closures for work zones require motorists to shift into another lane despite reduced visibility. Sequential warning lights affixed on temporarily deployed cones or barrels at the work zone taper can improve driver recognition of the lane closure by clearly delineating the lane taper area.
  • Crashes and queuing resulting from delayed driver recognition of traffic patterns in work zones at night
  • Increases safety in nighttime work zones by clearly defining lane taper
  • Increases early merging
  • Can reduce average speeds
Dynamic Lane Merge Dynamic lane merge is the broad term used to describe several types of merges that agencies can use at lane closure and merge locations. The system may include traffic sensors, trailers with solar-powered flashers, equipment and batteries, dynamic message signs, and communication devices. Types of merges include the following.
  • Lane-based signal merge: A strategy that employs a signal at the proper merging point to assign the right-of-way for traffic in each lane if the approaching volume exceeds 800 vehicles per hour per lane.
  • Dynamic early merge: When traffic congestion is low, signs encourage early merging to the through lane to avoid traffic disruptions from merges at the lane drop.
  • Dynamic late merge: When traffic congestion is moderate to high, signs encourage using all lanes to the merge point to reduce queue lengths.
  • Queuing associated with lane drop
  • Aggressive driving at the merge point and associated crashes
  • Delay associated with incident response at the merge point and congestion through the work zone
  • Right-of-way confusion
  • Improves road user safety by reducing the number of aggressive merges
  • Improves travel times through the work zone associated with normalized speeds and minimizes queuing
  • Lane-based signal merge increases vehicle throughput and, as a result, reduces the average vehicle delay, stopped vehicle delay, and the number of vehicle stops under congested traffic conditions
Providing Traveler Information
Dynamic Stopped Traffic Advisory Because queue lengths can vary greatly, identifying a suitable location for advanced warning signage is sometimes difficult without regularly altering the placement. The dynamic stopped traffic advisory system can be activated only when queues exist for determined lengths or sections of roadway, which may help to reduce travel times, decrease work zone congestion, and reduce the likelihood of back-of-queue crashes. The system also can be used to warn motorists about stopped traffic in situations where sight distance is impeded by roadway geometry, such as near horizontal or vertical curves.
  • Back-of-queue crashes related to little or no warning about queuing
  • Collects realtime or near-realtime traffic data
  • Provides motorists with information about queues and delays
  • Reduces rear-end crashes
Over-Dimension Warning Work zones may cause temporary minimal width or height clearances for large vehicles using the roadway. Efforts made on behalf of the transportation agency to reroute the affected vehicles may not be effective, so over-dimension warnings give compliance notifications as large vehicles approach the work zone.
  • Congestion and traffic mobility
  • Safety
  • Alerts drivers that their vehicle is over dimension and they need to use an alternate or escape route
  • Warns drivers about their inability to continue through the work zone, providing sufficient time to use an alternate or escape route
  • Tells drivers to stop when they fail to use the designated alternate or escape route
Portable Changeable Message Signs Portable changeable message signs are useful in situations that require advance notice, such as ramp or lane closures, narrow lanes, changing geometric conditions, or realtime travel information.
  • Significant queuing and delays
  • Changing travel conditions within the work zone
  • Work zone speed variability
  • Changes in roadway alignment and surface conditions
  • Provide travelers with realtime information on work zone conditions
  • Reduce speed variance
  • Increase effectiveness at night and during inclement weather
Work Zone Realtime Information System Portable queue detectors include video cameras mounted on poles in advance of work zones. System detectors collect lane occupancy and traffic speed data and send them to a computer connected to changeable message signage. The computer processes the data and, when it determines that backups are forming, it automatically displays warning messages on the changeable message signage.
  • Variability in travel time leading to traveler uncertainty
  • Potential for increased delay
  • Reduces congestion associated with lane closures
  • Reduces rear-end crashes and fatal crashes due to excessive queuing
  • Improves communication with the motoring public
  • Provides realtime, credible information resulting in better compliance with suggested actions for travelers


This van is equipped with technology to detect and record vehicle speeds through work zones automatically. Mounted cameras take photographs of a speeding vehicle’s license plate and driver.


Managing Speeds

The use of technology for speed enforcement in work zones has the potential to increase compliance and improve the safety of road users and workers. Excessive speeding in work zones contributes to increased frequency and severity of crashes. In addition, the speed differentials between vehicles before and after they enter work zones may be a contributing factor to crashes. Therefore, increasing motorists’ compliance with speed limits has the potential to decrease the speed variance and improve safety. This technology application can take several forms.

Technology-assisted speed enforcement employs technology such as radar or LIDAR (LIght Detection And Ranging) to indicate a motorist’s speed, or uses speed-over-distance systems that photograph vehicles at both start and end points to determine whether an infraction has occurred based on the calculated average speed.

Fixed-camera speed enforcement uses an automated fixed-camera unit that detects and collects data on speed violators, such as speed, date, time, location, and license plate information, and sends a ticket to the vehicle owner--all without human interaction.

Mobile speed photo enforcement may be deployed in vehicles or as freestanding roadside units with oversight typically administered by a law enforcement officer.

In 2006, the Illinois Department of Transportation (IDOT) began using speed photo enforcement as a means to reduce fatalities and severe injuries in work zones. When speed photo enforcement is deployed in a work zone, a sign informs drivers that the system is in use. The Illinois State Police and IDOT, in conjunction with a private vendor, deploy self-contained vans outfitted with this technology. The vans log an approaching vehicle’s speed and record when that speed exceeds a specified maximum. The vans are equipped with two onboard cameras: One captures an image of the driver’s face, while the other acquires an image of the vehicle’s rear license plate. The system also documents the date and time of the violation.

Mobile speed photo enforcement in Illinois is effective in reducing average speeds and increasing compliance with speed limits in work zones. The percentage of vehicles exceeding the speed limit near speed photo enforcement decreased from about 40 percent to 8 percent for passenger vehicles and from 17 percent to 4 percent for heavy vehicles such as trucks transporting commercial goods. Illinois found that average speeds in work zones were reduced by 3 to 8 miles per hour with speed photo enforcement.

An evaluation of speed enforcement technology in the United Kingdom showed that vehicles exceeding the speed limit were reduced at both fixed-camera sites (71 percent) and mobile-camera sites (24 percent). Speed-over-distance systems, a form of technology-assisted speed enforcement, can reduce speed by more than 12 miles (20 kilometers) per hour and lessen associated crashes.

IDOT also has experience with the use of radar speed trailers with speed feedback signs. Radar speed trailers may be supplemented with enforcement to achieve speed reductions over extended periods of time. “IDOT’s Bureau of Safety began requiring the use of radar speed trailers in the 2013 construction season on the entry to all of our interstate work zones,” says Ted Nemsky, engineer of construction with IDOT District 8. “We have noticed the traffic is slowing down when we use these units.”


Production Rates for Traditional and Automated
Deployment of Raised Pavement Markers

  Production Rates Exposure
(Per 12 hours of installation)
Locations of Use
Two-Lane Roads Four- (or More) Lane Roads
Traditional Replacement 750–1,500 markers per day 1,200–2,200 markers per day 72 person-hours Widespread
Automated Replacement Unknown 2,100 markers per day 24 person-hours California, Georgia, North Carolina


Reducing Exposure

Two of the most common devices to delineate work zones, raised pavement markers and traffic cones, have two commonalities: their installation requires considerable manual effort and necessitates that workers deploy the devices very near lanes of moving traffic.


GDOT uses this machine, developed by the Georgia Tech Research Institute, to install raised pavement markers automatically.


Manual placement of raised pavement markers exposes personnel to hazards and requires extensive labor hours and fleet needs. Workers typically are separated from highway traffic by only a few inches. A standard placement operation includes a six-person crew and four vehicles consisting of lead and following trucks and operations vehicles.

The Georgia Department of Transportation (GDOT) and Georgia Tech Research Institute have teamed up to develop a way to lessen the personnel and fleet needs associated with manual installation of raised pavement markers, while reducing worker exposure to traffic. Their automated placement system reduces the personnel needed to two--a vehicle driver and an operator to load the markers and adhesive into the installation device.


MnDOT deploys a nonintrusive technology in some work zones to detect trucks entering mainline traffic from a haul road and uses changeable and static message signs to alert motorists to prepare for trucks entering the traffic flow.


GDOT uses the automated system on multilane highways to limit worker and equipment exposure. Other advantages to the automated system include the following:

  • Changes a stop-and-go stationary operation to a continuously moving operation.
  • Reduces the need for multiple fleet vehicles to a single-vehicle operation.
  • Increases installation efficiency, minimizes wear and tear on the fleet, and improves the fuel mileage required by the installation process.
  • Improves safety by removing one or more laborers from exposure to live traffic.
  • Reduces the likelihood of workers suffering burns related to the hot bitumen adhesive used in marker placement.

Similar to the installation of raised pavement markers, manually deploying traffic cones requires workers to be in close proximity to moving traffic for setup and removal. Crews can use an automated traffic cone machine in any work zone that requires traffic cones, especially those covering a significant distance. A single operator can safely and quickly open and close lanes. The system uses just one vehicle to lay down cones automatically at regular intervals and then pick them up again later. The system also can retrieve cones that have been knocked over when hit by vehicles.

Preventing Incidents

Construction contractors can employ vehicle-activated detection to warn travelers about a potential conflict or the need to slow down because of equipment entering or exiting the mainline. As construction vehicles approach a detection system, installed at locations of work area ingress or egress, invehicle sensors communicate with a system installed at the perimeter of the work zone. The detection of construction equipment triggers changeable message signs or static signage along the roadway to display warning messages to mainline motorists.

The Minnesota Department of Transportation (MnDOT) uses nonintrusive detection to notify motorists about construction equipment entering or leaving work zones. MnDOT considers applying this technology in three specific scenarios. In the first scenario, construction equipment must use the mainline roadway to accelerate upon leaving the work area. In another scenario, the average daily traffic count on the mainline roadway is so high that drivers of construction equipment cannot easily recognize a gap in traffic to safely enter, or construction equipment crosses traffic at a location with limited visibility. A third scenario is when construction equipment must use the mainline roadway to decelerate and the roadway volume is above the level where traffic can safely adjust speed or change lanes. In each scenario, MnDOT uses the detection and messaging system to reduce the probability of vehicle collisions with construction equipment and provide for increased safety of construction workers. MnDOT also uses the technology to caution drivers not to follow construction vehicles into the work area.

Gathering Performance Data and Managing Traffic

Recent advances in traffic-monitoring technologies, battery power, and communications make it possible to more easily gather realtime data on traffic conditions around work zones. Agencies can use portable traffic-monitoring devices employing radar, cellular, microwave, and satellite technologies to monitor traffic conditions actively without a large investment of infrastructure or staff resources. Portable traffic-monitoring devices can detect queues and measure average travel speeds in key areas, such as in advance of and within transition areas for work zones. The devices also can store data for later analysis.

The California Department of Transportation (Caltrans) and the California Highway Patrol have discussed using portable traffic-monitoring devices to collect average speeds through work zones in order to assess key times for targeted speed enforcement. If the devices show average speeds that are consistently above the posted speed limits within work zones, the California Highway Patrol could deploy officers to enforce the speed limit.


To discourage drivers from following construction vehicles into the work zone, MnDOT’s system displays messages alerting motorists that trucks will be exiting the roadway ahead and reminding them not to follow the trucks.


A U.S. Department of Transportation report, Final Evaluation Report: North Carolina Deployment of Portable Traffic-Monitoring Devices, notes that in many work zones, the investment required to install and maintain full-scale temporary ITS equipment may be cost-prohibitive because of the ever-changing nature of road conditions and traffic. According to the report, traffic-monitoring devices that are permanently installed might be disabled during construction, or temporary traffic lanes might shift vehicles outside the devices’ detection area during construction activities. Portable traffic-monitoring devices eliminate these issues because they are highly mobile and relatively inexpensive. Crews can easily move these devices to new locations as needed and deploy more of them when traffic conditions dictate (for example, when queues are longer than expected). Typically, procuring portable traffic-monitoring devices requires a short lead time, and because they are easy to deploy and relocate, they minimize exposure of workers to traffic. These features increase the feasibility of data collection and traffic management in more work zones.

Managing Traffic At Nighttime

Nighttime lane closures for work zones require motorists to shift into another lane under conditions of reduced visibility. However, sequential warning lights affixed on temporarily deployed cones or barrels at the work zone can improve driver recognition of the lane closure by clearly delineating the lane taper.

Using wireless communication, warning lights give the impression of a single light source traveling along the defined taper limits in the same direction as motorists are traveling. A 2011 study on this application, Cost-Benefit Analysis of Sequential Warning Lights in Nighttime Work Zone Tapers, performed by the University of Missouri indicates a positive change of nearly 12 percentage points in the number of vehicles that merged early, indicating early recognition of the work zone taper.

Other benefits of sequential warning lights include helping to maximize traffic flow by better delineating the merge area and potentially reducing work zone crashes associated with merging at lane closures and queuing, increasing safety for both road users and workers. In addition, sequential warning lights are a low-cost improvement. Each light costs approximately $100 (only slightly more costly than conventional warning lights) and has a battery life of more than 1,000 hours.

Providing Traveler Information

End-of-queue crashes are a concern in work zones where congestion tends to develop, particularly when queuing is unexpected. This type of crash is often severe because it usually involves a large speed differential between the approaching vehicles and the stopped traffic. In congested conditions, any crash is likely to increase traffic backups and lead to more crashes. However, technology such as queue warning systems can effectively reduce end-of-queue crashes.

According to MnDOT’s Guideline for Intelligent Work Zone System Selection, technologies for dynamic advisories for stopped traffic have the ability to address several issues associated with work zones. For example, queue lengths may vary greatly, even hour-by-hour, making it difficult to predict suitable locations for advance warning signage for temporary traffic control. Queue lengths also may encroach upstream beyond a motorist’s reasonable expectations for stopped traffic, and geometrics may cause poor visibility of end-of-traffic queues, shortening reaction times and causing panic stopping. In addition, queues initiated on crossroads may cause traffic conflicts and delays on mainline highways (for example, backups that go beyond the length of ramps and through or around turns at intersections). The MnDOT report cites the system’s benefits as including reduction in rear-end crashes, increased diversion of traffic to alternate routes, and ample time for motorists to respond safely.


A sensor housed within this orange barrel is part of an end-of-queue warning system that can help prevent crashes in work zones.


A queue warning system uses detection components paired with variable or dynamic message signs, or static signing with interactive flashers. Crews deploy the detection devices upstream of the work zone at successive intervals where they anticipate queues. Each detection device communicates with its own set of sign components, either activating prepopulated messages such as “Stopped Traffic Ahead/Be Prepared to Stop” or “Speed Ahead 30 MPH/Prepare to Stop,” or activating flashers on the static signing that might read “Be Prepared to Stop When Flashing.”

Because queue lengths can vary greatly, placing static warning signs is challenging. With a dynamic advisory system, messaging changes based on traffic speed and queue length. The system also can warn motorists about stopped traffic in situations where sight distance is impeded by roadway geometry, such as near horizontal or vertical curves.

“The Texas Department of Transportation [TxDOT] is using several types of technology to make the many work zones in the central Texas portion of I–35 safer and easier for travelers,” says Bobby Littlefield, Waco district engineer with TxDOT. “Systems that provide realtime monitoring of current conditions, estimates of future conditions, and localized advance warning of queues caused by lane closures have all been implemented to help travelers plan their trips and safely reach their destinations. In addition to the benefits for travelers and workers, the system is providing a wealth of data for performance monitoring.”

Using technology for queue detection and warning can be particularly effective when queues are unpredictable and therefore unexpected by drivers. When it is difficult to predict when and where queues will occur, it can be challenging and costly to use manual methods, such as to have sufficient staff available to cover extended time periods, and to keep the warning device (enforcement vehicle or truck-mounted dynamic message sign) in the proper location relative to the end of the queue.

In an analysis of a queue detection and warning system implemented at several work zones by IDOT, crash statistics from 2010 (prior to system implementation) and 2011 (after system implementation) showed nearly a 14-percent decrease in queuing crashes and an 11-percent reduction in injury crashes. These reductions occurred despite a 52-percent increase in the number of days when temporary lane closures were implemented.

Challenges and Tips to Deploying Technology

Practitioners deploying these systems have sometimes encountered challenges, such as the cost of deployment, which can limit their consideration, or can result in elimination from the project late in the design phase. As in other areas of technology, practitioners may have difficulty staying abreast of current technologies, especially if their primary expertise is design or construction. ITS staff members often do not interact with construction staff, leading to reduced understanding of work zone issues by those with the technology expertise. Similarly, design and construction staff may have limited awareness of what technology is available, a reluctance to use technology or ITS, or difficulty in using it effectively.

Further complicating these decisions is the wide range of options available, as well as barriers to choosing the most appropriate and effective applications. For example, some new products have limited performance records. And, although others may have been deployed, varying conditions make it tough to estimate performance under different work zone conditions with many variables. A lack of clear goals for using technology on a project can hinder decisionmaking and decrease the likelihood that the selected technology will meet expectations.

These challenges, however, are not insurmountable. By clearly identifying project impacts and potential issues, practitioners can develop management strategies (technology or otherwise) for work zones that will address those needs. Using a structured process, such as systems engineering, helps to define needs and develop specifications. This type of approach and tips for how to apply it are described in a recent publication from the Federal Highway Administration (FHWA) called Work Zone Intelligent Transportation Systems Implementation Guide (FHWA-HOP-14-008). When deciding whether to use technology, practitioners should consider expected impacts, duration of the work zone, performance goals, and the availability of existing equipment. Like other tools for managing traffic in work zones, technology should be used as part of an integrated set of strategies in a TMP.


MnDOT uses this stopped traffic advisory system to alert motorists when work zone-induced delay downstream is a significant concern. Changeable message signs activate in response to traffic when a queue is detected within 1 mile (1.6 kilometers) of the sign's location.


To help guide its decisionmaking, IDOT is establishing a policy for the use of different types of smart work zone systems. “One of our key lessons learned was that we need to develop a tiered statewide contract special provision for ITS that will allow for competition between all smart work zone systems and establish a policy to guide where we want to use these different types of systems,” IDOT’s Nemsky says. “In the past, it’s been decided on a project-by-project basis based on [our] knowledge of the project area, traffic incident data, and sight distance issues. We also do queuing analysis for all interstate projects. We are envisioning having three different tiers in our policy and special provisions to recommend different types of smart work zone technology based on factors such as whether a project is on an urban or rural interstate and what level of delays are anticipated.”

In addition, when considering whether to lease or buy technology, practitioners should examine factors such as the planned amount of use; how quickly the technology is likely to change; maintenance needs and expertise of staff; cost; and whether the equipment, if procured, could be permanently deployed.

Communication among design and construction staff and ITS staff within an agency can help with effectively planning, designing, procuring, and deploying technology. Practitioners also can benefit from the knowledge and experiences of their peers when making decisions about technology in work zones. FHWA sponsored a peer exchange in May 2013 to facilitate discussion on the use of technology in work zones. The findings from the peer exchange, as well as recent case studies describing States’ experiences using technology in work zones, are available on FHWA’s work zone Web site at

Tracy Scriba is the Strategic Highway Research Program 2 (SHRP2) program coordinator in FHWA’s Office of Operations. She is the former program manager of FHWA’s Work Zone Management Program, where she led many aspects of FHWA’s research, policy, and technology transfer related to work zones. She holds a B.S. in systems engineering from the University of Virginia.

Jennifer Atkinson, P.E., is a senior transportation engineer for Leidos with more than 13 years of public and private sector experience in transportation design, traffic operations, highway safety, and work zone mobility and safety.

For more information, visit or contact Tracy Scriba at or 202–366–0855.