ITS Safety and Mobility Solutions Improving Travel Through America’s Work Zones
“ITS Safety and Mobility Solutions – Improving Travel Through America’s Work Zones” provides an overview of the commonly used ITS applications that are easily implemented into any work zone. This brochure is intended to aid design/traffic engineers, transportation agencies, and construction contractors on the ITS tools which are competitively available to help increase the mobility and safety through any work zone. For more information on Work Zone ITS, contact the American Traffic Safety Services Association (ATSSA) at 1-800-272-8772 or visit www.ATSSA.com.
Acknowledgments Andrew Kramer National Capital Industries, Inc. President
Joseph M. Jeffrey Road-Tech Safety Services Vice President
Brian Nicholson ADDCO, Inc. CFO & COO
Steve Kite, P.E. North Carolina DOT Work Zone Traffic Control Project Engineer
Jim Babcock Stay Alert Safety Services, Inc. General Manager
Jacques Legault Sales Manager Daktronics
Douglas A. Bernard Quixote Transportation Safety Director of Government Relations
Tracy A. Scriba Federal Highway Administration Operations Core Business Unit
Rob Bushman International Road Dynamics, Inc. Advanced Applications Engineer
Ken Smith Ken Smith & Associates President
Michael Granger Street Smart Rental, Inc. Owner
Marvin L. Sohlo, P.E. Minnesota DOT Work Zone Standards Engineer
Jeff Grossklaus, P.E. Michigan DOT Work Zone Quality Engineer
Martin Weed Washington DOT/Traffic Operations State Work Zone Engineer
Thomas Hicks, P.E. Maryland SHA Director, Office of Traffic & Safety
William W. Wellman Solar Technology, Inc. National Sales Manager
Jon Jackels, P.E., PTOE Minnesota DOT Work Zone & Pavement Marking Engineer
Kenneth C. Wood FHWA - Midwest Resource Center Traffic Operations Engineer
The typical intelligent work zone layout illustrations were provided to ATSSA for its use in the “ITS Safety and Mobility Solutions” publication through the courtesy of Mn/DOT.
Table of Contents
Introduction........................................................................................................4 Typical System Components.............................................................................6 Definitions of Terms..........................................................................................8 Resources............................................................................................................9 Changeable Speed Limits................................................................................10 Alternate Route Systems................................................................................12 Travel Time......................................................................................................14 Expected Delay................................................................................................16 Dynamic Lane Merge Control System............................................................18 Automated Work Zone Speed Enforcement......................................................22 Oversized Load Detection.................................................................................24 Construction Vehicle Entering and Exiting the Project......................................26 Work Space Intrusion......................................................................................28 Stopped or Slowing Traffic Warning...............................................................30 Excessive Speed Warning Systems..................................................................32 Water Over Pavement Detection System.........................................................34
Introduction Roadway work zones can impede traffic flow and reduce the predictability of driving conditions. Traffic congestion and the resulting delays through work zones are a major complaint of users of America’s roadways. In response, the Federal Highway Administration (FHWA) has amended regulations to better respond to issues surrounding work zones. (FHWA Work Zone Safety and Mobility Rule. For information and discussion, visit http://ops.fhwa.dot.gov/wz/resources/final_rule.htm.) The FHWA Work Zone Safety and Mobility Rule was developed to reduce congestion and road user delay and to encourage broader consideration of safety and mobility impacts of work zones beyond the project itself to address corridor, network, and regional road user mobility.
Work Zone ITS systems may be designed to notify drivers of: • Traffic delays and their causes • Adverse environmental condi tions such as rain, fog, or ice • Unexpected road hazards • Possible detours and alternate routes • Changes in speed limits • Lane closures • Unsafe travel speeds
Many well-developed Work Zone ITS systems are capable of: • Minimizing driver frustration in congested work zone queues • Providing adequate time for road users to respond to the message conveyed and to take the appro“Work Zone Intelligent Transportation Systems priate action (ITS)” refers to using technology to support • Increasing roadway capacity more traditional work zone management and • Aiding law enforcement in work operational techniques. A Work Zone ITS sys zones tem should be portable, automated, and reliable. • Allowing transportation agencies It should analyze traffic flow in real-time and to accurately measure and evaluprovide updated, accurate information and guid- ate roadway mobility provisions ance to drivers. for contractor incentives/disin centives Work Zone ITS systems may integrate work zone equipment with computers, communiWhen these systems are integrated into the work cation, and sensor technology. Components zone, many benefits are achieved, which may include input devices such as traffic detectors, improve safety of both drivers and road workers information processing devices such as comput- while also increasing mobility. ers and output devices that display road user information, such as changeable message signs. The development of this publication was made possible through funding provided by ATSSA. The primary benefit of a Work Zone ITS system ATSSA’s core purpose is to advance roadway is to improve mobility while improving safety for safety. We believe that if a single life can be both the motorist and the highway worker. These saved through this project, the effort will have systems provide accurate, real-time information to been worthwhile. road users so they can make informed choices.
Consider for Use
REAL-TIME INFORMATION SYSTEM
Typical System Components After extensive research and product development, today’s Work Zone ITS components can withstand and properly operate in the most demanding of work zone environments. Wireless communication allows data to be collected and transmitted between components. System installation and maintenance can be performed by trained staff members, without the need for an electrical engineer or manufacturer’s representative to be on site. The availability and decrease in cost of electronic components, and the increase in manufacturers producing Work Zone ITS systems has made these systems affordable. Today, the benefits far outweigh the cost. Work Zone ITS components perform the following functions: • Collect data such as vehicle speeds and vehicle presence • Verify the accuracy of data • Transmit the data to other system components • Store and manage data for other contract performance requirements • Analyze the data to provide the proper instructions or information to give road users • Provide real-time video of the work zone to aid decision making regarding lane closures or incident management response Detection components used to collect roadway data may include: • Acoustic • Piezo-electric • Global Position Systems (GPS) • Pneumatic road tubes • Infrared • Radar • Magnetic • Ultrasonic • Microwave • Video Data exchange between components may be transmitted using: • Cellular telephone • Radio frequencies • Hard wired cable • Satellite • Optical • Wireless access points Instructions or information may be relayed to road users and workers by many means, including, but not limited to: • In-vehicle GPS • 511 system • Permanent ITS systems • Audible alarms • Portable changeable message signs (PCMS) • Broadcast e-mails • Public media announcements • CB radio channels Visual alarms • Highway Advisory Radio (HAR) • • Internet Web sites
Consider for Use
SOLAR-POWERED, TRAILER-MOUNTED MICROWAVE DATA COLLECTOR
Definitions of Terms Advisory Speed: A recommended speed for vehicles based on the current roadway conditions or operating characteristics. Advisory speeds are not enforceable. Benefits: Anticipated affects on mobility and safety when the system is properly designed and deployed. Mobility and safety measures may be within the work zone or surrounding network, and may include the public, the workers, or the constructability of the project. Changeable Message Sign (CMS): A sign that is capable of displaying more than one message. This sign is changeable manually, by remote control, or by automatic control. The device is considered “portable” when trailer mounted. The device may be operated in one of two modes: • Standard Mode: The message is programmed to remain displayed until changed by the operator or via a timer . • Dynamic Mode: The message is programmed to respond to traffic operating characteristics or roadway conditions. Devices (components): The individual parts or subsystems that make up a working Work Zone ITS system. Examples include: cameras, various detectors, signs, data monitoring or recording equipment, communication systems, work zone devices, and remotely activated alarms. Options: Various options may be available for portions of the Work Zone ITS systems. The options should be considered when they achieve satisfactory results with lower levels of “system complication” and cost. Speed Limit: The speed applicable to a section of highway, as established by law. Static Sign: A message for the motorist is printed on a standard sign, either regulatory, warning or guide signs. Static signs may be ground-mounted or mounted on portable sign structures. System: A combination of devices integrated to monitor traffic operating characteristics or roadway conditions and react with a predetermined response. Travel Delay: The estimated amount of extra time the motorist will incur due to traffic conditions in a work zone located downstream. Generally useful for spot locations at a great distance away from the motorist’s current location, which provides alternate route possibilities. Travel Time: The estimated amount of drive time from the motorist’s current location to an identified location, generally limited to approximately 10 miles maximum distance. Work Zone ITS System: An automated system of devices that provides motorists and/or workers with real-time information for improved safety and mobility through a work zone. The devices are integrated to monitor traffic operating characteristics or roadway conditions and react with a predetermined response.
Resources FHWA Intelligent Transportation http://www.ops.fhwa.dot.gov/wz/its/index.htm AAASHTO ITS in Work Zones http://www.transportation.org/?siteid=42&pageid=1939 Automated Work Zone Information Systems http://www.itsbenefits.its.dot.gov/its/benecost.nsf/0/F1F2919AE17E081285257172005C85 69?OpenDocument&Query=BApp Guide of Intelligent Work Zone System Application Selection Minnesota Department of Transportation http://www.dot.state.mn.us/trafficeng/workzone/iwz/MN-IWZToolbox.pdf Midwest States Smart Work Zone Deployment Initiative: MwSWZDI Technology Evaluations Year One - Chapter 5: Nebraska - SpeedGuard Radar Speed Reporting System http://www.itsbenefits.its.dot.gov/its/benecost.nsf/0/004EE2E7933C311685256D34004BA6 FF?OpenDocument&Query=BApp National Cooperative Highway Research Program - Guide to Contracting ITS Projects By: Kenneth R. Marshall Philip J. Tarnoff Edwards and Kelcey and Independent Consultant Baltimore, MD Rockville, MD NCHRP Report 560 Guide to Contracting ITS Projects - Speed Reduction Effects of Speed Monitoring Displays with Radar in Work Zones on Interstate Highways http://www.itsbenefits.its.dot.gov/its/benecost.nsf/0/8F2306948210535B8525726000748E7 2?OpenDocument&Query=BApp Portable Non-Intrusive Traffic Detection System (PNITDS) - Research Of Existing Portable Systems (September 18, 2003) Prepared by: Minnesota Department of Transportation and SRF Consulting Group, Inc. Office of Traffic, Security and Operations One Carlson Parkway, Suite 150 395 John Ireland Boulevard, MS 725 Minneapolis, MN 55447 St. Paul, MN 55155-1899 (763) 475-0010 (651) 284-3438 Use of Innovative Traffic Control Devices to Improve Safety at Short-Term Rural Work Zones http://www.itsbenefits.its.dot.gov/its/benecost.nsf/0/F61943DF4661F59E85257260007508B 4?OpenDocument&Query-BApp Variable Speed Limits http://www.itsbenefits.its.dot.gov/its/benecost.nsf/0/F3678455A0AF3277852572600064861 9?OpenDocument&Query=BApp
Changeable Speed Limits Selecting the appropriate work zone speed limit for a work zone is a challenge. For driver compliance, the posted speed limit needs to be reasonable, and if drivers do not see a need to reduce their speed, they will not. This is especially true for long-term work zones with commuter drivers. When activities require workers to be near open lanes of traffic and unprotected by a barrier, when lane closures are required, or when geometric conditions of the open roadway change, reductions in work zone speed should be considered. The Work Zone ITS system allows the posted speed limit value to be changed to an appropriate, enforceable “work zone speed limit” during the work activity. When the activity stops, the speed limit is changed back to the normal posted speed for the roadway. During a 24-hour period, the speed limit may change several times. Before implementing changeable speed limits, check state and/or municipal speed limit administrative procedures.
Benefits • . • • •
Allows speed limits to be changed quickly using wireless technology to match the requirements of the work activity Are portable and can be moved to new areas were speed management is needed. Are often recognized better by drivers than static regulatory speed limit signs due to the use of modern electronic displays. Drivers must see the speed limit in order to comply. Encourages compliance of the speed limit. This reduces variations in speeds, which increases roadway capacity and may reduce crashes within the work zone.
Consider for Use • • • •
When the project is long term in duration, requiring multiple phases, with each having variable affects on the travel way. When closed lanes are reopened at the end of the work day with no lasting effects on the travel way. When the location of the day’s work activities do not always require a reduction in speed. When manually covering or removing speed limit signs is unsafe.
Alternate Route Systems Work Zone ITS systems that monitor delay through a work zone can provide valuable trip planning information on a regional basis. Good communication along a particular roadway corridor can help drivers make informed decisions about their travel plans. To do this, the cities and transportation districts inform each other when lane closures are planned, and then share this information with roadway users by way of internet web sites, 511 traveler informational systems, public media announcements, highway advisory radio (HAR), and permanent ITS systems. It is common that a work zone, using traditional work zone applications, on a major roadway linking two major destinations, can result in lengthy delays upwards of one or two hours. Queue buildups can result in rear-end and secondary crashes, which can cripple the roadway corridor. Wasted fuel, excessive emissions, and unproductive driver time add to this inefficient equation. A Work Zone ITS system’s software can monitor queue length and process speed detection data along the roadway corridor. Various types of communication technology can be used to distribute real-time information that can be displayed on permanent ITS message boards or portable changeable message boards. The information can also be broadcast on HAR along the route. This traveler information can be included on many GPS systems, including those used by interstate trucking companies. Messages may include the location of the expected delay, anticipated delay time, and/or possible alternate routes.
Benefits • Provides real-time information so road users can better plan their routes and travel times. • Advises drivers to seek alternate routes. • Reroutes traffic in order to: • Reduce work zone traffic congestion, which decreases fuel consumption and emissions. • Reduce traffic demands on roadway sections under construction. • Allow for more efficient material delivery, which expedites work progress. • Reduce the potential for work zone crashes. • Helps relieve driver anxiety by providing increased knowledge of the situation.
Consider for Use • •
When roadway accommodates long-distance, regional travelers who desire an alternate route that provides the lowest travel time to the next major populated area or major roadway interchange. When a viable alternate route exist that can help absorb travel demand through the work zone.
Travel Time Travel time/expected delay information systems provide real-time travel information to motorists to allow them to make informed decisions and to help relieve their frustration. Moreover, these systems provide the user with a sense of awareness related to the traffic congestion ahead. Work Zone ITS systems can provide real-time information to road users in two ways: travel time information and expected delay information. Both of these methods are based on congestion and delay within and approaching the work zone. These systems should be considered whenever a work zone may cause additional travel time when compared to a typical travel day. States and/or municipalities may set their own threshold of extra estimated travel time before considering using a system, but 10 to 15 minutes are general thresholds used. Travel Time Information System • Travel time systems calculate the time to travel from the motorist’s current location to a point beyond the work zone congestion. • Time calculations for travel time systems are considered to be accurate on a route up to approximately 10 miles long. Therefore, changeable message signs providing the travel time information should be located within 10 miles of the destination point (generally the end of the work zone). • Travel time systems are limited to restricted access roadways with no traffic signals or any significant all-way stop intersections. • Typically, information from travel time information systems is considered a better fit for commuter traffic since regular users will notice time differences on a daily basis. • When travel time cannot be determined, the expected delay system should be used.
Benefits • •
Informs drivers of the estimated travel time between their current location and a specific destination beyond. Provides drivers with sufficient travel information. This may calm drivers tempers and ease frustration associated with travel delay.
Consider for Use
When driver delay is anticipated to exceed 10 to 15 minutes. When project creates excessive delay in an urban area.
Expected Delay Expected Delay Information • Estimated delay time systems calculate the increase in time due to a work zone. • Time calculations for travel delay systems can be estimated for any work zone delay. The changeable message signs providing the travel delay information may be placed anywhere in advance of the work zone, but should not be used interchangeably with travel time systems. • Because “travel time” is a better choice for direct distances less than 10 miles long, the “estimated delay” system is generally used for posting times for work zones located much beyond 10 miles from the motorist’s current location. • Estimated delay time systems do not consider “normal” or “estimated” travel times to arrive at the work zone congestion location, therefore, in-route traffic signals and time variables are eliminated. • Multiple PCMS locations may be deployed depending upon the availability of alternate routes. • Delay time information is considered better for non-commuter traffic, including travelers from outside of the area, because previous knowledge of the total trip time is not required.
Benefits • •
Informs drivers of the expected delay time between their current location and a specific destination beyond. Provides drivers with information that will allow them to decide whether to change routes or notify others of their estimated arrival time. It may also provide drivers with sufficient information to calm tempers and ease frustration.
Consider for Use • • •
When road user delay is anticipated to exceed 10 to 15 minutes. When causing traffic congestion on a roadway used extensively by interregional traffic. When an accurate travel time cannot be accurately determined to an individual cross street or destination.
Dynamic Lane Merge Control System The traditional merging lane closure method is well understood by road users. This operation normally works well during most of the day when traffic demand is less than the capacity of the open lane. However, when the demand exceeds the capacity, congestion develops and road rage intensifies. Aggressive drivers remain in the closed lane up to the actual merge point. In response, sign-abiding drivers do not let the aggressive drivers merge. The resulting traffic backup continues to grow and typically will extend upstream beyond the advance lane closure signs. When this happens, drivers unfamiliar with the lane closure approach the end of the queue at high speed. This increases the likelihood of rear-end crashes. There are two new work zone techniques that use Work Zone ITS technology to address these problems. The first is the early merge, which is intended to encourage the aggressive drivers to merge into the open lane sooner than they would with the traditional merging lane closure. The second method is the late merge, which encourages all drivers to remain in their lanes until they reach the merge point. Dynamic merge control systems aim to improve driver behavior by providing a clear way to understand the traffic control method. This concept ensures that some vehicles are not waiting for a long time while others, familiar with the lane closure, find a way to get in front to reduce their delay. The “fairness” of the systems has been found to reduce road rage or other aggressive driving actions. Using Work Zone ITS technology, the safest and most efficient merging operation can be implemented by dynamically switching from the conventional merge to either the early merge or late merge when congestion is detected.
Early Merge System The objective of the early merge is to move vehicles out of the closed lane upstream as soon as possible. The dynamic early merge system uses ITS sensors to monitor traffic in the open lane on the approach to a work area. As vehicles begin to slow down and queues start to develop, advance warning signs with the message “Do Not Pass When Flashing” are activated. These signs are installed adjacent to the closed lane at ¼ to ½ mile intervals in advance of the lane closure. When slow or stopped vehicles are detected in the open lane next to the sign, a wireless signal is transmitted to activate the next sign upstream.
Benefits • • • • •
Matches the length of the Early Merge System application to the upstream roadway demand. Reduces aggressive driving and unsafe merge maneuvers. Provides significant advanced warning so drivers have adequate distance to merge. Gives drivers positive instructions on lane usage and merging points, which helps reduce road rage and misunderstandings between drivers. Compliance to lane assignment may be enforceable by law enforcement.
Consider for Use • • • • • •
When the work zone requires a two-to-one or three-to-two lane drop. When peak hour traffic demand is between 2,000 and 3,000 vehicles per hour for a two-to-one lane closure and between 3,000 and 3,800 for a three-to-two lane closure. When the length of queue is not expected to extend beyond the start of work zone signing. When there is commuter traffic and sufficient project duration to allow adaptation to the system. When travel speed is high. When aggressive, repeat drivers attempt to “jump the queue” by remaining in the dropped lane up to the merge point.
Dynamic Lane Merge Control System Late Merge System The dynamic late merge is the opposite of the early merge. It is intended to encourage drivers to use all available lanes until they reach the beginning of the merging taper. When congestion forms, changeable message signs are activated to provide the following lane use instruction: • Located upstream of the taper beyond the estimated maximum queue length: “Stopped Traffic Ahead” alternating with “Use Both Lanes”. • Located upstream of the taper at the estimated queue length when the dynamic late merge will be activated: “Merge Ahead” alternating with “Use Both Lanes”. • Located at the desired point of merge: “Take Turns” alternating with “Merge Here”. Using ITS technology, the safest and most efficient merging operation can be implemented by switching between the conventional merge and the late merge when congestion is detected.
Benefits • • • •
Alerts drivers that they are approaching slow or stopped traffic. Allows queue to “stack” in multiple lanes, which reduces the overall queue length by approximately half. Reduces the differential in speed between lanes, providing for safer lane changes. Gives drivers positive instructions on lane usage and merging points, which helps reduce road rage and misunderstandings between drivers.
Consider for Use • • • •
When the work zone requires a two-to-one lane drop. When traffic demand exceeds the capacity of the open lane. When traffic demand could create an extensive queue length which may affect other access points or may extend beyond reasonable placement of advance warning signage. When congestion caused by lane closures varies many times throughout a work day.
Automated Work Zone Speed Enforcement Excessive speed through roadway work zones continues to be a safety concern for workers, transportation agencies, and law enforcement agencies. Over the last decade, in an attempt to increase awareness of speed limits within roadway construction projects, many states have enacted “Double Fines in Work Zones” laws. Yet, without enforcement, these laws did little good. Enforcement that is evident to the driver allows them to realize that speed limit signs are important and must be obeyed. While traditional speed enforcement can be effective, it can be dangerous to both road users and law enforcement officers. Work zone environments may restrict the ability of officers to set up radar. Violators may have difficulty finding a safe place to pull over, since work zone environments sometimes have limited shoulder space. Additionally, speed enforcement may create traffic congestion and increase the potential for work zone crashes. Automated speed enforcement using ITS technology is one tool that can be used to reduce work zone speeds and crashes. These systems combine radar and image-capturing technologies to detect speeding vehicles and collect digital photographic evidence. The owner of the vehicle is then mailed a citation including a photo of the vehicle, vehicle license plate, and the detected vehicle speed. The process is similar to systems that catch road users running red lights. ITS automated speed enforcement systems are being used in several states. Prior to installing any automated enforcement system, be sure to check local statutes to see if they are allowed.
Benefits • • • •
Increases driver awareness of the work zone. May increase 24-hour compliance to work zone speed limits without law enforcement officers present. Allows law enforcement officers to focus on other job duties. Eliminates officer’s exposure to hazardous roadside traffic stops.
Consider for Use • • •
On roadways where the temporary traffic control zone has narrowed shoulders and limited roadway exit points for speed violators and law enforcement to safely exit the travelway. When 24-hour speed enforcement is desired. On projects where law enforcement availability is limited.
Oversized Load Detection Overheight or overwidth loads can create mobility challenges and worker safety issues through our nation’s work zones. Unfortunately, those that cause the greatest havoc are typically unpermitted loads traveling at night. Damage may be minor, like hitting portable temporary traffic signals, or major, like the load getting wedged under a bridge structure. This can cause several hours of delay and congestion while working to remove the load and repair the damage. When project construction phases require pavement work that decreases bridge clearance heights or significantly reduces lane width, the use of a non-intrusive Work Zone ITS oversized detection system can identify oversized loads and then display warning instructions on a portable changeable message sign or activate flashing beacons to direct the driver to use an alternate or escape route. Variations of these systems may provide auditory or vibratory alarm systems that can be placed near or on the workers in the work area to alert them that the oversized load system has been activated.
• • •
Provides dynamic alert message to the driver that their load is oversized and they are required to use an alternate route or must stop. Provides warning to roadway workers that an oversized load is approaching that may intrude into their work space. Helps prevent damage to roadway structures and work zone devices.
POLE MOUNTED OVERHEIGHT DETECTION SENSOR
Consider for Use • • •
When work activities reduce height clearances below minimum requirements. When roadway corridor is frequently used by unpermitted, illegal oversized loads. On roadways with high truck volumes.
Construction Vehicles Entering and Exiting the Project Haul Trucks Exiting or Entering the Roadway Roadway construction projects require large quantities of offsite materials to be transported into and from the work area. Haul trucks exiting the roadway to enter the work activity area or reentering the roadway can cause a disruption to the traffic flow. Typically, the work area entrance and exit points are short openings in the barrier wall or small gaps in the line of channelizing drums with little or no area for trucks to decelerate to exit, or accelerate to reenter, the roadway. Ideally, motorists react by slowing down or changing lanes, but many motorists are caught unaware of the truck’s speed or maneuvers, and they must react immediately by panic braking or swerving into other lanes. It is also not uncommon for drivers to follow haul trucks exiting the roadway, and is more common in nighttime projects. Using Work Zone ITS systems located near the haul road entrance or exit point, a portable changeable message sign located upstream with the appropriate driver message such as “Truck Entering/ Exiting Roadway, Reduce Speed” can be activated to warn motorists of approaching truck traffic only when trucks are detected. Real-time messages gain motorists’ trust and respect.
Haul Trucks Crossing the Roadway When haul trucks cross a roadway, the Work Zone ITS system can warn approaching drivers that a truck crossing is ahead and that a truck is crossing. This system may or may not give right-of-way to the truck, but at a minimum, it informs the approaching traffic that they need to pay attention and possibly slow down to allow the haul truck to safely cross.
Benefits • . • • • •
Alerts drivers of slowly accelerating trucks preparing to enter or cross the roadway. Alerts drivers of decelerating trucks preparing to exit the roadway and warns drivers not to follow the trucks. Provides real-time information to road users so they can slow down, change lanes, or prepare to stop. Decreases tailgating when the system is activated. Reduces crashes involving haul trucks and secondary crashes upstream.
Consider for Use • •
On work zones where site distance is limited, especially for high speed, rural roadways. In areas where there is an increase in the potential conflicts between construction vehicles and the motoring public.
Work Space Intrusion Work Zone ITS intrusion warning devices provide both errant drivers and road workers effective warning indications. Vehicle detectors identify errant vehicles which have entered the closed lane. Detection systems throughout the entire work zone could improve reaction to errant drivers who enter the zone at any point. When an intruding vehicle is detected, changeable message signs are activated to display “Stop Now,” and sirens and horns will sound in the work zone. Wireless interconnection between vehicle detectors, dynamic message signs, sirens, or horn alarms allows the work zone to extend the buffer space for an errant vehicle to safely decelerate and stop once they realize their mistake. From the worker viewpoint, the extended buffer space allows more time to escape the work area if the errant vehicle continues to proceed. An alternative type of alarm is an “on body” pager worn by workers. When an errant vehicle is detected, a wireless signal is sent to the pager which activates an auditory or vibratory alarm. Using Work Zone ITS technology, vehicle detectors can be located at positions not used by work crews, material hauling trucks or equipment; yet at the proper location to detect an intruding vehicle. This increases the reliability of the system by reducing “false alarms,” which were common in many early-generation intrusion alarm systems. Continued research into these Work Zone ITS systems is expected to further enhance our understanding and mitigation of work space intrusion. Research and development of these systems is encouraged and seen as a viable method to reduce death and injury in our nation’s work zones.
Benefits • • •
Improves work production and quality by allowing on-foot workers to focus on their work rather than watching vehicles passing near their work site. Detects vehicles and warns workers of the danger before the errant vehicle is seen by the work crew. This is important during nighttime work, because drowsy or impaired drivers are more likely to intrude into a work zone. Allows workers longer time to escape through early detection and warning of errant vehicles entering the work space.
Consider for Use • • •
When the work activity area is near the edge of the traveled way. When the work activity area is near an exit or entrance ramps. Often, drivers are focused on the task of entering or exiting the roadway and they errantly enter the work activity area. When work is performed at night.
Stopped or Slowing Traffic Warning Slowing and stopped traffic is one of the most common causes of work zone crashes. A single driver’s reaction to activities in the work zone environment can have immediate effects on the highway upstream, well beyond the limits of the work zone. When drivers have to suddenly transition from posted speeds to a stopped position, they may behave unpredictably and erratically. Work Zone ITS queue detection tools monitor the speed of vehicles within and upstream of the work zone. When reduction in travel speed is detected, changeable message signs or other warning systems are activated to warn approaching drivers that they should be prepared to stop. The upstream effects of slowed or stopped traffic vary day to day and hour by hour. However, Work Zone ITS tools allow real-time collection of data, resulting in current messages being displayed to drivers.
Benefits • • •
Alerts drivers of slowing or stopped traffic so they can safely stop. Reduces rear-end and secondary crashes. Helps reduce driver anxiety by giving advanced warning of stopped or slowed traffic, reducing the need to apply the brakes.
Consider for Use • • • • •
When stopped traffic is not expected, particularly when visibility is restricted or when transitioning from a rural to urban driving environment. When lane closures are required on high volume roadways, especially during peak hours. When work is being performed near high volume entrance or exit ramps on high speed roadways. When work is performed at night on a high volume roadway. On roadways where stopped or slowing traffic occurs daily, especially during peak hours, when sight distance is limited.
Excessive Speed Warning Systems Excessive speed warning ITS can warn individual drivers of their unsafe speed. The system displays a message to the driver that they are exceeding a predetermined threshold speed which is considered to be unsafe for the roadway condition or geometry. Example messages such as “Slow Down, Sharp Curve Ahead,” or “Exceeded Speed Limit, Reduce Speed Now” can be customized to match the traffic control application. This system can also be combined with a dynamic speed display (more commonly referred to as a “your speed is” system). Excessive speed warning ITS gives the work zone designer an additional tool to get the driver’s attention when traditional temporary applications such as static warning and speed limit signs are unsuccessful.
Provides real-time warning aimed at an individual driver. Helps reduce crashes or intrusions into the work area.
Consider for Use • • •
When changes in roadway alignment require temporary sharp curves, or limited sight distance. When other Work Zone ITS systems are being used, such as “Water Over Pavement Detection” or “Stopped or Slowing Traffic,” the excessive speed warning system can be coordinated to warn a speeding driver to slow down and prepare for changes in pavement conditions or congested traffic ahead. When an individual driver needs to take immediate action to reduce their speed to avoid a severe consequence.
Water Over Pavement Detection System The combination of flooded pavement, high speeds, obstructed vision, and the element of surprise can have deadly results in a work zone environment. During major reconstruction projects, it is often necessary to detour travel lanes to accommodate the various phases of work. For example, bridge widening on a divided freeway may require a median cross over, with both directions of travel sharing one side of the freeway. These changes in geometry and the addition of a temporary barrier to separate traffic can adversely affect roadway drainage, increasing the potential for unexpected vehicle hydroplaning. A single out-of-control vehicle can cause a multi-vehicle chain reaction crash with deadly consequences. For projects where drainage issues are a concern, a hydroplane detection/alert system using Work Zone ITS technology is the solution. This system uses water detection sensors to determine if water is present, and if needed, measure the depth of the water. Then, roadside controllers and wireless communications activate appropriate driver warning messages on a PCMS. When the pavement is wet and the water level is below a predetermined level, the PCMS message can be “Wet Pavement Ahead; Observe Speed Limit”. When the water exceeds the predetermined level, the PCMS message can display “Standing Water Ahead; Reduce Your Speed”.
Benefits • • •
Provides real-time information to warn drivers of water over the pavement. This is especially important during the night. Provides advanced warning messages, typically slowing traffic speeds and increasing following distances, which may reduce the potential of multi-vehicle crashes. Notifies the contractor when high water is present using a pager system so corrective measures can be taken.
Consider for Use
When roadway drainage could be potentially slowed due to the installation of a temporary barrier or changes in pavement cross slope. On projects with extensive excavation near drainage structures.
WATER/ICE DETECTION SYSTEM