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Construction work zones are a common cause of congestion, injury, and fatality. According to the Federal Highway Administration (FHWA), more than 800 fatalities and 37,000 injuries occur in the U.S. every year at construction sites along freeways and urban roads. Of the fatalities, over 400 are road workers. Increasing amounts of vehicle emissions at work zones have also become a serious environmental problem.
In an effort to more safely and efficiently manage traffic in work zones, the U.S. Department of Transportation (USDOT) has incorporated the Maintenance and Construction (MC) Management Service into the National ITS Architecture (link to our Architecture section). The MC Management Service focuses on the following ten functional areas:
- Maintenance and Construction Vehicle and Equipment Tracking
- Maintenance and Construction Vehicle Maintenance
- Road Weather Data Collection
- Weather Information Processing and Distribution
- Roadway Automated Treatment
- Winter Maintenance
- Roadway Maintenance and Construction
- Work Zone Management
- Work Zone Safety Monitoring
- Maintenance and Construction Activity Coordination
The work zone management and safety monitoring services are intended to enhance the safety and operational efficiency of work zones for all road users (e.g. motorists, pedestrians, motorcyclists, and bicyclists) as well as roadway workers. ITS applications, like traffic management, traveler information dissemination, and enhanced incident detection and management, will improve roadway safety and operational efficiency.
The kinds of ITS technologies used at work zones depend on the goals of the particular traffic management center (TMC) overseeing the zone. These goals may include providing information to travelers on traffic routing, detours, and significant incidents; minimizing congestion at work zones; and enhancing traveler safety. These goals are usually achieved through the following processes:
- Traffic data collection
- Traffic data analysis
- Traveler information dissemination
- Data archiving
The ITS technologies used to meet these goals are typically the following:
- Closed circuit television (CCTV)
- Traffic sensors and queue detectors
- Telecommunications technologies (to provide communication between road sites, road operators, and road users)
- Central server
- Highway advisory radio (HAR)
- Portable variable message signs (VMS)
- Dynamic late merge (DLM) systems
- Automatic workzone information systems (AWIS)
The above ITS technologies work together. CCTV cameras record images of incidents while traffic sensors and queue detectors collect traffic speed and congestion level information. The traffic imagery and sensor data is sent via wireless communications (link to telecommunications diagram of CCTV) to a central server at a TMC. In some cases, the central server's software will calculate traffic volume and speeds, and then automatically broadcast this information to drivers. Otherwise, a staff person monitoring the TMC manually sends incident information to travelers via VMS, HAR, and other media. VMS messages may advise or inform drivers of anticipated delays, alternate routes, and suggested travel speeds.
Recent developments in VMS technology include portable travel time prediction systems that predict and display real-time travel time for motorists before and through work zones. The systems use microwave radar sensors to detect vehicles in freeway lanes, a microcontroller to calculate traffic volume and occupancy for each lane, and radio signals to transmit this traffic information to a personal computer. The PC runs software that uses an intelligent traffic algorithm and travel-time estimation model to calculate travel times; the travel time information is then sent via radio signals to a VMS. A typical message generated by this system might read "28 MIN TO END OF WORKZONE."
Recently, the dynamic late merge (DLM) system and the automatic workzone information systems (AWIS) have been deployed. DLM is usually placed right before the lane closure point of a work zone. The DLM System is designed to better utilize early and late merge strategies, eliminating conditions where motorists typically experience conflict when merging. Through the use of portable variable message signs (PVMS) and sensing technologies, the DLM traffic control strategy dynamically changes instructions based on current traffic conditions. The strategy changes the merge point location, enabling the system to direct drivers to merge early if there is light traffic and merge late if traffic is congested.
AWIS is a traveler information system specific to drivers passing by a work zone area. A typical AWIS integrates traffic sensors and PVMS with a central controller. The central controller automatically determines, based on the detected traffic condition, messages for PVMS. Because AWIS presumably provides useful real-time traffic information to motorists as they approach or pass through a work zone, its direct benefits are assumed to include increasing safety for both motorists and construction personnel by adjusting drivers’ speeds and reducing anxiety.
ITS applications at work zones have improved driver safety and made traffic management more efficient at construction sites. The telecommunication lines connecting roadway sensors, Traffic Management Centers (TMC), and drivers have enabled an efficient exchange of information. When accurate advisory information is communicated to drivers upstream of work zones, fewer incidents (i.e. rear-end collisions and backups) result and drivers are able to make more informed choices about alternate routes. The relationships between transportation departments, the public, and other agencies have generally improved as a result of the ITS technologies network used for work zone projects. For instance, incident response teams were able to communicate better with traffic management centers because of the timely and accurate real-time traffic data they received.
- Reduced backups and delays.
- Motorists can make more informed decisions about route choice.
- ITS minimizes the impact of a full road closure.
- Reduced rate of traffic citations in the work zone (dynamic information on the number of citations issued is posted on variable message signs (VMS) upstream of the work zone; this reduces the number of traffic violations, such as speeding, in these zones.)
- Traffic data can help contractors avoid or minimize operations during peak periods.
- TMC personnel can better determine how long a backup will last.
- Rear-end collisions are reduced.
- Agencies are able to more quickly identify locations of problems (i.e. merges, ramps, or work zone configuration) and suggest the appropriate changes.
- Costs are reduced when personnel can more accurately determine the severity of an incident and how to respond to it.
- Some ITS work zones do not require full or part-time staff to monitor CCTVs or manually change VMS signs (i.e. the central server software automatically calculates traffic flows and volumes and sends predetermined traffic information messages to VMS or traffic websites.)
- Traffic information provided at strategic locations allows travelers to take alternate routes.
- Travelers are informed of backups ahead, thereby decreasing the likelihood of rear-end crashes and driver frustration.
- Delays are reduced when a TMC knows when peak travel periods occur and can avoid having a contractor on the road during those times.
The cost of applying ITS to a work zone depends on an agency's decision
to lease or purchase its system and whether the systems is temporary
or permanent.
- ITS-based work zone systems need to have a reliable telecommunications
network that can allow each component to collect and relay the
appropriate traffic information.
- Drivers must receive accurate traffic information and advisories
about the presence of work zones, potential delays, incidents
ahead, and upcoming lane merges.
- All relevant agencies need to be adequately informed of their
impending role in traffic management at a work zone in order to
ensure the efficient application of ITS at that zone.
Across the U.S., including:
- Springfield, Illinois
- Lansing, Michigan
- Albuquerque, New Mexico
- West Memphis, Arkansas
- Minneapolis/St. Paul, Minnesota
- Santa Clarita, California
Springfield, Illinois
The Illinois Department of Transportation (IDOT) reconstructed the
Lake Springfield Bridges on I-55 south of Springfield, which involved
closing the southbound bridge and diverting southbound traffic onto
the northbound bridge. A barrier wall separated traffic on the bridge,
causing drivers to reduce speeds from 55 to 45 mph. The process
was reversed when the southbound bridge was complete.
To improve traveler information and mitigate incidents in the work
zone, the IDOT operated several ITS technologies continuously for
the duration of the project. These included remotely controlled
variable message signs, traffic sensors, CCTVs, and a central server.
The CCTVs and traffic sensors collected traffic flow, speed, and
incident data, which they sent via wireless communications to the
central server (additionally, the CCTV images were archived.) The
base station server then processed this data (i.e. calculated volume
and traffic speeds) and disseminated the appropriate information
to travelers via VMS and the Internet; IDOT staff were updated via
e-mails when, for instance, longer queue lengths were detected.
After ITS was applied to this work zone, the IDOT did not report
any significant backups.
Lansing, Michigan
In 2001, the Michigan Department of Transportation (MDOT) instigated
a construction project that involved the total closure of I-496
in downtown Lansing. Full closure of this segment of the freeway
required traffic to be diverted around the construction zone. To
avoid incidents and backups, the MDOT implemented an ITS-based system
that displayed advisory messages to travelers. They used CCTVs to
capture traffic images; queue detectors to collect flow data; and
a software package to gather and process traffic data and transmit
it to drivers via VMS and the MDOT website. These ITS applications
allowed motorists in the I-496 work zone to make more informed route
decisions; the video images allowed staff to quickly identify and
locate incidents.
Albuquerque, New Mexico
From March through June 30, 2000 the New Mexico State Highway and
Transportation Department (NMSHTD) rebuilt "The Big I"
interchange in Albuquerque to make it safer, more efficient, and
more easily accessible. The NMSHTD's goals for implementing ITS
at this work zone were to provide traveler information on traffic
routing, detours, and significant incidents; to minimize capacity
restrictions due to incidents by more quickly identifying and responding
to incidents; and to enhance traveler safety.
To achieve these goals, the NMSHTD used CCTV cameras that captured
traffic images and sent them via wireless communications to a central
server. Incidents were manually identified by staff, who then alerted
a safety service patrol of the problem. The central server held
prepared advisory messages, which a staff member sent out to the
variable message signs (these messages could have been sent out
automatically as well). Information concerning the work zone was
also available to the public online (http://www.thebigi.com)
and through highway advisory radio (HAR). As a result of these ITS
applications, incident response times dropped and drivers experienced
fewer delays. The NMSHTD was also able to better assess the magnitude
of incidents and the level of response needed.
West Memphis, Arkansas
In 2000 the Arkansas State Highway and Transportation Department
(AHTD) reconstructed three miles of concrete pavement on I-40. To
avoid significant backups on the bridge located close to the work
zone, the AHTD installed queue detectors that sent traffic flow
information to a central server via wireless communications. Based
on pre-programmed traffic condition scenarios, this central server
sent out advisory messages to drivers via variable message signs
(VMS) and highway advisory radio (HAR).
The ITS technologies enhanced the safety and efficiency of the
I-40 work zone. The automatically updated VMS signs required fewer
TMC staff, and the information provided to travelers reduced the
number of rear-end collisions.
Minneapolis/St. Paul, Minnesota (DLM)
Minnesota Department of Transportation (MnDOT) deployed DLM systems at three different locations around the Minneapolis/St. Paul metropolitan area during the summer of 2004. The locations were I-494 (northbound and southbound) in Plymouth, US 52 in St. Paul, and I-35 around Lakeville.
Evaluations of the system revealed that some drivers were confused by or did not comply with the signs. This reduced the effectiveness of the system. It was also shown that DLM is not needed when volumes are consistently less than 1500 vehicles per hour per lane for a work zone with one lane open.
Santa Clarita, California (AWIS)
An AWIS system, called Computerized Highway Information Processing System (CHIPS), was deployed in June 2003 in the work zone site located in the City of Santa Clarita, north of Los Angeles, on freeway I-5. It was evaluated from June 30th, 2003 to September 6th, 2004 with respect to four specified aspects, functionality, reliability, effectiveness, and cost.
The effectiveness of the system was evaluated based on three criteria: safety, diversion, and responses from travelers. The results of these studies showed that (1) the driving environment after the use of AWIS seemed safer; (2) obvious diversion were observed on two evaluation dates, July 6th, 2003 and September 1st, 2003; (3) positive responses about the system were obtained from driver surveys. It was found that AWIS provides most functions desirable for work zone traffic management. However, reliability of the system needs to be further improved.
A
Benefit-Cost Analysis for the Use of Intelligent Transportation
Systems Technology for Temporary Construction Zone Traffic Management
on the I-496 Reconstruction in Lansing, Michigan, Submitted
by: Joseph A. Kratofil, Jr., March 2001.
Informed
Motorists, Fewer Crashes: Using Intelligent Transportation Systems
in Work Zones (FHWA brochure)
Intelligent
Transportation Systems in Work Zones: A Cross-Cutting Study, FHWA,
November 2002.
Maintenance
and Construction User Service: An Addendum to the ITS Program,
Prepared by SAIC& TransCore, January 2001
Evaluation of 2004 Dynamic Late Merge System. Minnesota Department of Transportation, Prepared by URS, December 2004.
Evaluation of Automated Workzone Information System (AWIS) – CHIPS (Computerized Highway Information Processing System). Submitted by Lianyu Chu, Hamed Benouar, Will Recker, August 2005.
Criteria for Portable ATIS in Work Zones, prepared by Vikas Lachhwani and Alan J. Horowitz, October 2005.
Author: Lauren Smith
Last Update: 10/03/06 By Xuegang (Jeff) Ban
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