Project Details
TPF-5(367)
05/01/19
07/31/23
University of Nebraska at Lincoln
Researchers
About the research
Concrete barriers (CBs) are widely used to direct vehicular traffic in construction work zones. For bridge applications, CBs have a critical role to prevent vehicles from departing the travelway until permanent barriers can be installed. For roadway applications, they not only provide the flexibility of guiding the flow of traffic, but also protect the construction personnel and equipment from potential accidents. A critical aspect to ensure the proper performance of CBs is to leave ample empty space behind the barrier. This space is essential to accommodate the lateral deflection of the barrier when it is subjected to vehicle impact loads. While a “less than sufficient” space may magnify the consequences of accidents for motorists and construction workers, a “more than sufficient” space will take away the much needed work area for construction activities. To avoid the listed issues, the required space is determined based on the design of the barrier and how it is connected to the supporting structures/surfaces. One category of design is free-standing temporary barriers, which can be conveniently installed, repositioned, and removed. While the issue of connection to the ground surface is completely eliminated in such barriers, they suffer from the excessive impact-induced lateral deflections that cannot be accommodated in the most of practical cases. To limit the lateral deflection of barriers, especially where limited space is available, anchoring, pinning, or bolting techniques must be used to restraint the barrier to the underlying ground. This, however, may cause significant damage to the bridge deck or pavement (1) at the time of installation, (2) when an accident occurs, and (3) at the time of removal. This is one of the main motivations of the project, which aims at identifying the potential CBs that do not require, or significantly reduce, anchoring to the supporting structures/surfaces.
Researchers
Ali Kamyab
Stephen Andrle
About the research
Moving work zones have fewer traffic control devices than stationary work zones and provide no buffer space for vehicles that encroach on a work zone. To improve the safety of moving operations, the Iowa Department of Transportation (Iowa DOT) created a six-inch fluorescent yellow-green (FYG) background for the work zone signs that are mounted on the back of work zone vehicles.
Undoubtedly the FYG background creates a clear contrast between the orange sign and an orange Iowa DOT truck that follows a moving work area. This study examined the impact of the sign?s improved visibility in encouraging drivers to make an early merge to the open lane prior to a lane closure.
The analysis of data indicates that overall right-lane traffic volumes, recorded during the seven days of data collection after the background placement, were two percent less than the traffic observed in the “after” condition. The study concludes that the difference between the right-lane traffic observed in the “before” and “after” conditions is indeed statistically significant at the 95 percent confidence level.
Project Details
05/01/02
12/31/02
University of Nebraska at Lincoln
Researchers
Ali Kamyab
About the research
As traffic volumes increase above the roadway capacity, traffic backups occur. These backups typically begin just prior to the merge point and grow until the volume through the work zone is less than the volume approaching the work zone. The ROADHOG sensors detect the presence of traffic backup prior to lane closures at work zones by the decreases in the speed and headway and increases in the volume and lane occupancy. Based on the preset system parameters, the RPU then activates display devices to provide visual warning to approaching motorists. By providing drivers with advance warning, it is assumed that traffic will approach the end of the queue more cautiously, avoiding high speed rear-end collisions.
Researchers
Ali Kamyab
Tom McDonald
About the research
As traffic-related work zone crashes continue to increase across the nation, safety of road users and workers has become a top priority for transportation agencies. Since inattention and irresponsible behavior by drivers are surmised to contribute to the frequency of work zone crashes, a program featuring extraordinary presence of and enforcement by law officers has been implemented in many states to address this concern. A literature search of such programs and related research was conducted. While the overall benefits of these activities have been found positive, much of the evidence has been anecdotal. To assess the scope of extra work zone enforcement programs, a survey was developed and distributed to state departments of transportation across the nation. This survey sought information regarding these efforts such as criteria for selection of target work zones, methods of enforcement operations, and beneficial results. A special survey was also designed and distributed to enforcement agencies in Iowa and other selected states. In addition to the surveys, personal contacts and office visits were conducted by the research team staff.
The study found that use of extra enforcement in work zones is a common practice in many states and these activities appear to be increasing. Current literature, survey responses, and interviews have all indicated a prevalent opinion for the benefits of increased law enforcement presence and activity in work zones. Very few comments offered conclusions of negative impacts, such as additional congestion, from these efforts. However, the beneficial effects of focused enforcement have not been intensively quantified. In addition, procedures for the use of law officers in work zones are quite inconsistent across the nation, as is the general implementation of specific legislation addressing work zone traffic violations. Similar variation can be found in funding levels and sources for enforcement activities in work zones among the states. Training of law officers prior to work zone duty does not appear to be commonly required, though the value of focused training is being recognized in some states.
As crashes and deaths continue to rise annually in our nation?s work zones, it is imperative that demonstrated beneficial programs such as the expanded use of law officers in these locations be continued, refined, and expanded. Future study is needed to supplement the knowledge base and provide guidance to agencies when considering the use of law enforcement to calm traffic, ensure compliance with traffic laws, and thus provide for safer work zones.
Researchers
Patrick McCoy
About the research
None available for this project