Information from driver studies performed during the first year of the project identified several features and conditions that created confusion and anxiety in traversing the work zone. Many of these conditions represented deficiencies in the work zone traffic control from the standpoint of positive guidance principles. This report describes the efforts to tailor the application of positive guidance procedures to work zone traffic control installations reviews. Four key steps, hazard visibility assessment, expectancy violation determination, information load analysis, and information needs specification, are described in the context of traffic control at potentially complex work zones. A methodology is presented for applying these steps in a field review process to be performed as part of the work zone traffic control installation process.
Highway departments, which are responsible for maintenance of different highway facilities, have the continuing responsibility to make the highway as safe and efficient as possible. Traffic control approaching and within a work-zone is a major concern for these departments. The objective of this study was to test three traffic control devices white lane drop arrows, orange rumble strips, and the CB wizard alert system for their effectiveness in improving merging, and reducing speed and speed variance at an interstate highway work-zone in Missouri. Statistical tests were conducted on the speed related data collected along the approach to the work-zone lane closure when the devices were not in place and when they were in place. Results of implementing the white lane drop arrows and the CB wizard alert system indicate decreases in the percentage of vehicles in the closed lane, mean speed and speed variance. It also appears that the CB wizard alert system may be more effective than the white lane drop arrows. The CB wizard alert system in conjunction with the orange rumble strips did show similar reductions, but they were much smaller in comparison to the CB wizard alert system alone.
Safety hazards are increased in highway work zones as the dynamics of a work zone introduce a constantly changing environment with varying levels of risk. Excessive speeding through work and maintenance zones is a common occurrence which elevates the dangers to both drivers and motorists in the work zone. Although most work zones are controlled by reduced speed limits or state law enforcement, driver adherence to these regulations and laws in very minimal, especially in work zones. Several studies have shown a correlation between speeding in work zones and traffic crashes which lead most traffic safety professionals to conclude that excessive speeding and speed variance are the contributing factors in a large percentage of traffic crashes, injuries or fatalities. The most influential factor in achieving speed compliance in the work zone is the driver's perception of heightened risk. The main objective of this study was to determine the safest and most effective countermeasure for the reduction of vehicular speeds within construction and maintenance work zones. The purpose of the simulator experiment was to determine the effectiveness of 20 countermeasures on the reduction of speed through work zones in a controlled laboratory setting. The literature review identified several past research studies utilizing speed reduction countermeasures in work zones and under normal traffic conditions. From this review, 20 countermeasures were selected for evaluation based upon discussions with ODOT personnel.The post hoc tests indicated that the presence of construction workers, presence of construction vehicles, law enforcement, speed photo enforcement and shifting lanes were most effective at reducing speeds in work zones. The least effective speed reduction countermeasures included 3 sets of 3 rumble strips, concrete barriers, other channelizing devices and changeable message signs with speed reductions less than 10 mph.
The primary objective of the research was to identify and evaluate effective ways of improving traffic operations and safety on congested freeways. There was particular interest in finding condition-responsive traffic control solutions for the following problem areas: (1) end-of-queue warning, (2) work zones with lane closure, and (3) queue spillover at exit ramps. Available techniques considered by this research include combination of static and dynamic queue warning systems, dynamic merge control in advance of freeway lane closures, and various traffic control strategies, such as traffic diversion and ramp metering, to mitigate queue spillover at exit ramps. Three sets of evaluation studies were conducted: first, two queue warning systems deployed on IH 610 and US 59 in Houston, Texas, were evaluated based on field observations. Second, strategies to resolve a ramp spillover problem at an exit ramp in El Paso, Texas, were analyzed using traffic simulations. Third, the Dynamic Merge work zone traffic control concept was evaluated using traffic simulations, and recommendations were developed for its potential use for various work zone types with different lane closure configurations.
Periodic resurfacing, rehabilitation, restoration, and reconstruction work is needed on the aging highway system to maintain a desired level of service for the traveling public. However, temporary work zones on highways disrupt the normal flow of traffic and reduce the level of service. Freeway work zones have become a major source of traffic congestion and travelers' delays which result in reduced freeway capacity, increased driver frustration, increased traffic accidents, increased road user delay cost, and increased fuel consumption and vehicle emissions. In this research, scientific models have been created for estimation of the work zone capacity for the first time. A case-based reasoning (CBR) model has been created for freeway work zone traffic management considering work zone layout, traffic demand, work characteristics, traffic control measures, and mobility impacts. A freeway work zone traffic delay and cost optimization model has been developed in terms of the length of the work zone segment and the starting time of the work zone using average hourly traffic data. An adaptive computational model has been created for estimating the work zone capacity and queue length and delay. A neuro-fuzzy logic model has been developed for estimation of the freeway work zone capacity taking into account 17 different factors impacting the work zone capacity. An object-oriented model has been developed for freeway work zone capacity and queue delay and length estimation. The model has been implemented into an interactive software system, called IntelliZone. IntelliZone's capacity estimation engine is based on pattern recognition and neural network models incorporating a large number of factors impacting the work zone capacity. This research provides the foundation for a new generation of advanced decision support systems for effective management of traffic at work zones. The extensive parametric study of main factors impacting the work zone capacity provides quantitative and objective results of value to work zone engineers and highway agencies when creating traffic management plans for work zones.
Pavement and shoulder edge drop-offs commonly occur in work zones as the result of overlays, pavement replacement, or shoulder construction. The depth of these elevation differentials can vary from approximately one inch when a flexible pavement overlay is applied to several feet where major reconstruction is undertaken. The potential hazards associated with pavement edge differentials depend on several factors including depth of the drop-off, shape of the pavement edge, distance from traveled way, vehicle speed, traffic mix, volume, and other factors. This research was undertaken to review current practices in other states for temporary traffic control strategies addressing lane edge differentials and to analyze crash data and resultant litigation related to edge drop-offs. An objective was to identify cost-effective practices that would minimize the potential for and impacts of edge drop crashes in work zones. Considerable variation in addressing temporary traffic control in work zones with edge drop-off exposure was found among the states surveyed. Crashes related to pavement edge drop-offs in work zones do not commonly occur in the state of Iowa, but some have resulted in significant tort claims and settlements. The use of benefit/cost analysis may provide guidance in selection of an appropriate mitigation and protection of edge drop-off conditions. Development and adoption of guidelines for design of appropriate traffic control for work zones that include edge drop-off exposure, particularly identifying effective use of temporary barrier rail, may be beneficial in Iowa.
