Sequential Warning-Light System for Work-Zone Lane Closures

The late merge traffic control strategy has been proposed as a way to improve flow at work zone lane closures by maximizing queue storage space and creating more orderly merging. The late merge instructs drivers to use all lanes to the work zone taper and then take turns proceeding through the work zone. There is little information available on when the late merge should be used, however, and a limited understanding of the factors that influence its performance. This paper discusses the results of a simulation study of the late merge concept using microscopic traffic simulation. The late merge concept was evaluated by comparing it with traditional traffic control, through a full factorial analysis. Results of the computer simulations showed that the late merge produced a statistically significant increase in throughput volume versus the traditional merge for the three-to-one lane closure configuration across all combinations of analysis factors. Although the two-to-one and three-to-two configurations did not show significant improvement in throughput overall, it was found that as the percentage of heavy vehicles increased, the late merge did foster higher throughput volumes than traditional traffic control. The results of the simulations indicate that the late merge may not provide as much of a benefit as previous studies had indicated and that the area of application for the late merge may be limited to situations where heavy vehicles constitute more than 20% of the traffic stream.

A series of field evaluations were conducted within work zone lane closures on rural freeways in Michigan to determine 1) the optimal positioning of a speed feedback trailer (SFT) approaching an active work area, 2) the effectiveness of a digital speed limit (DSL) sign for posting work zone speed limit reductions, and 3) the effectiveness of a speed feedback panel paired with a DSL. Speed trajectories were collected for vehicles traversing each work zone using a series of handheld light detection and ranging (LiDAR) guns operated by a team of technicians seated in unmarked vehicles within each lane closure. The SFT was found to be increasingly more effective at reducing speeds of vehicles approaching and entering the work area as it was positioned closer to the work area. Positioning the SFT 200 ft from the start of the work area, which was determined to be the optimal position, reduced speeds entering the work area by 3.1 mph compared with when the SFT was positioned further upstream. This SFT position helps ensure that motorists receive timely feedback within sight of the work area while providing sufficient deceleration time to maximize speed reductions as drivers enter the work area. The use of a DSL to reduce the work zone speed limit from 60 mph to 45 mph reduced vehicle speeds by 3.7 mph near DSL. Furthermore, activation of the speed feedback panel that was on the same assembly as the DSL reduced vehicle speeds by an additional 1.8 mph.

The reduction of upstream end-of-queue (EOQ) crashes at work zone lane closures has been a focus of the Texas Department of Transportation, Austin, for several years. An ongoing widening effort on Interstate 35 through central Texas prompted officials to examine and implement technologies to mitigate the impacts of EOQ warning crashes. An EOQ warning system was established, which consisted of a highly portable work zone intelligent transportation system of easily deployable radar speed sensors linked to one or more portable changeable message signs and highly portable transverse rumble strips. The EOQ system was deployed upstream of nighttime lane closures, where queues were expected to develop. Although the sample sizes were relatively small, the trends did suggest that the systems were having a positive effect to reduce crashes. Overall, the EOQ warning system was estimated to have reduced crashes 44% from what they otherwise would have been if the system had not been used. The crashes that did occur were less severe, which was most likely because fewer of them were of the high-speed, rear-end-collision variety. With traditional societal crash cost values updated to 2014 dollars, the use of the EOQ warning system at nighttime lane closures reduced crash costs by $1.36 million over the analysis period. This figure equated to $6,313 in crash cost savings per night of deployment. Compared with the approximate costs of procurement and deployment of these systems, a break-even point was achieved after 95 to 190 nights of use.

Research conducted to explore the effects of natural diversion on traffic conditions and travel patterns upstream of temporary work zone lane closures on high-volume urban freeways in Texas is described. Specific objectives were to explore how natural diversion affects traffic volumes at the exit and entrance ramps upstream of the lane closures and the interrelationships between the freeway and frontage road operating conditions that develop at a closure and the amount of natural diversion that occurs. The field studies showed that the rate of queue growth upstream of the short-term lane closures diminished significantly after the first hour at each site. Eventually, the queues approached a balanced state in which the upstream end of the queue became almost stationary. This stabilization was due to significant reductions in entrance ramp volumes both upstream of the freeway queue and within the limits of queuing, as well as to changes in exit ramp volumes within the queue. As a result of these ramp volume changes the constrained flow rate within the queue increased as a function of the distance upstream of the actual lane closure. Using the theory of shock waves in a traffic stream it was shown that the changes in ramp volumes and resulting impact on constrained freeway flow rates within the queue were consistent with the queue stabilization process observed at each site.

Estimation of the capacity of work zones is vital to manage the possibility of traffic flows exceeding capacity and resulting in unbearable queues during work zone lane closures. A plethora of research papers have studied several ways to estimate work zone capacity, with the Highway Capacity Manual (HCM) having its own methodology to estimate capacity based on various site characteristics. However, HCM always recommends validating its model with local data to reflect the actual driving behavior of the region. This study considered work zone capacity as a function of queue discharge rate (QDR), defined as the 15-min average flow rate immediately after breakdown, also known as postbreakdown flow rate. By collecting data from 10 different work zones within the state of Louisiana, the study estimated QDR and its corresponding duration at breakdowns. An average QDR of 1,664 pcphpl and an associated queue of 120 min average duration was found. Analysis of variance showed that average QDRs across all sites were not significantly different. The QDR prediction model revealed that a closed right lane and a work zone on linear roadways significantly increased the discharge rate. However, the presence of nearby exit ramps, daytime scenarios, and an increase in the speed ratio and truck percentages were found to decrease the discharge rate. A separate model for the duration of queue or breakdown found the time of day, change in the speed ratio, presence of entry ramp, location of work zones, and annual average daily traffic of the roadway to be significant variables.

The study proposes the association between work zone types and work zone lane closure types used in the construction of South Korean expressways through the use of the text mining and association analysis techniques. Of the factors that greatly affect the capacity of work zones, work zone lane closure types and night work were analyzed. Words were extracted from the narrated work types using the text mining technique, and the associations among the words, lane closure types, and night work variables were identified. The analysis revealed a significant difference between the work types associated with main lane closure and shoulder lane closure. It is expected that this study can be effectively applied to establishing transportation management plans (TMPs) for work zones.

Passenger road transport plays an important role in the functioning of the state. This thesis can be substantiated by the fact that passenger road transport performs an important social task — the transportation of passengers. Passenger road transport is fully integrated into the transport system of the country and its subjects. The article considers three main types of activities in which passenger road transport is involved. The authors refer the commercial transportation of passengers to the first type, the transportation of passengers for the own needs of the carrier company to the second, and the use of passenger road transport as a means of individual mobility to the third. If we consider these groups from the point of view of the openness of information on them in various databases, then the first type of activity is the most informative, and the second and third are the least informative. Currently, there is no tool for qualitative and quantitative assessment of the impact of passenger road transport on gross regional products (GRP) and their components. This leads to inadequate reactions in the control system, for example in the field of passenger transportation. Increasing the validity of the development of passenger road transport systems by improving the accuracy of assessing its impact on the socio-economic development of regions is an urgent scientific and practical task. The working hypothesis is that passenger road transport is one of the key factors influencing the development of the subjects of the Russian Federation. Finding the relationship between the qualitative and quantitative assessment of the impact of passenger road transport on GRP and their components will create an understandable and informative tool for assessing the socio-economic condition of the subject in particular, and the country as a whole. The work uses methods of system analysis, mathematical statistics, in particular, correlation and regression analysis. When analyzing the data and processing the results, the authors used the discovery of information databases. The aim of the work is to create theoretical prerequisites for an analytical platform for managing the structure of the passenger vehicle fleet in the regions. The scientific novelty of the study lies in the revealed relationship between the number of passenger vehicles and the gross regional products of the constituent entities of the Russian Federation (correlation coefficients from 0.57 to 0.79), as well as parts of gross regional products by industry (correlation coefficients from 0.07 to 0.9). For the first time, an indicator of the number of conditional passenger motor transport units in the region is proposed, which gives an integral assessment of the methods of passenger motor transport correspondence, taking into account the categories and classes of vehicles. The practical significance of the study lies in the creation of a modern tool for managing passenger transportation in the constituent entities of the Russian Federation by improving the process of operating passenger road transport and managing the number, categories and classes of passenger vehicles. Directions for further research are to apply the above methodology to the integrated management of transport systems of the constituent entities of the Russian Federation.

The paper provides methodologies for microscopic simulation modelling of freeway work zones with lane closures in the proximity of interchanges. In addition, the research presents simulation results using calibrated modelling parameters to determine the capacity available for mainline flow under various operating conditions. The results will help researchers or practitioners with designing and studying freeway work zone sites under various lane configurations using better estimates of delays and queue sizes in the proximity of interchanges. Additionally, a 2 to 1 on-ramp merge condition was explored to predict the merge ratios under both demand and service flow conditions. The paper illustrates how ramp demand affects the share of segment capacity available to mainline traffic to reveal strategies for controlling this demand (via ramp metering for example) in order to maintain a prescribed freeway capacity through the work zone. The overall study result indicates the degree to which the presence of a work zone with lane closures decreases the proportion of mainline flow and shows the degree to which differences in work zone lane configurations affect merge and weave scenarios.

The impact of work zones on mean travel time and travel time reliability has gained attention as agencies focus on performance measurement. Travel time reliability in work zones often has been difficult for agencies to quantify because of the time and expense required to collect travel time data. Several private-sector companies have begun to sell travel time data; this availability has created an opportunity to examine cost-effectively work zone impacts on travel time reliability on a broader basis. The Virginia Department of Transportation recently acquired probe vehicle-based travel time data for 2010 from a private-sector data provider. These data were used to calculate measures of travel time reliability at 15 work zones and to examine factors that affected travel time reliability. Travel time reliability was quantified with 95th percentile travel time, a buffer index, and a planning time index. The work zones experienced a statistically significant degradation across all measures of travel time reliability as compared with baseline conditions. Work zone mean buffer index, planning time index, and 95th percentile travel time rates were higher by 48%, 18%, and 16%, respectively. Although lane closures occurred during off-peak periods, work zones that involved lane closures experienced increases in their mean buffer index, planning time index, and 95th percentile travel time with rates of 67%, 23%, and 22%, respectively. Annual average daily traffic per lane and the number of access points per mile were found to have the most obvious relationships with declines in reliability at work zones.

This paper examines risks associated with peak period lane closure during construction or maintenance work on urban freeways. In accordance with recently implemented policy by the Colorado Department of Transportation, lane closure would be allowed if reserve capacity were available. A relatively minor accident in the work zone caused substantial delays during the peak period that virtually paralyzed traffic in the Denver, Colorado, metropolitan area. This occurrence caused reexamination of the existing lane closure policy. Generally speaking, if a contractor is allowed greater flexibility in establishing work schedules, including the ability to work through peak periods, a lower bid can be expected. This paper compares savings in the cost of construction related to allowing lane closure during peak periods with the cost of potential incident-related delays in the framework of a quantitative risk analysis.

Freeway work zones with lane closures can cause traffic disruption and congestion with increased travel time, safety risks, and emissions.Variable speed limit (VSL) control has been widely studied to mitigate the negative impacts of work zone lane closures.To ensure effective VSL control, accurate detection of traffic conditions is important.However, stationary sensors from distant upstream or merging areas of a work zone can only provide location-based detections, which may not be sufficient for effective VSL control.Therefore, this study proposes a VSL control system for a smart work zone with a weighted traffic density estimation algorithm using data from stationary sensors and connected vehicles (CV).With location-based traffic detections from distant upstream and merging areas of a smart work zone, data from CVs in locations between the stationary sensors are used to obtain the weighted density.This weighted density is then fed to a feedback VSL controller, which can dynamically define the appropriate speed limits to reduce the negative impacts of the work zone closures.The proposed VSL controller was implemented and evaluated under a calibrated freeway work zone environment using the traffic simulator SUMO.The results show that the system can provide accurate traffic density estimation and effectively improve traffic mobility, safety, and environmental sustainability near the work zone area.

This study explored the impact of in-vehicle messages relative to roadside messages to alert drivers to events within a simulated work zone, in order to determine if these messages can improve driving performance within the work zone. Safety risks in work zones are usually mitigated by design standards and clear signage to communicate work zone information to drivers. Due to distraction and other driving task demands, these signs are not always noticed by motorists, nor are they always followed when they are noticed. The driving simulation tested drivers in two different types of work zones, shoulder work, and lane closure. Participants drove through these work zones three times, each with different messaging interfaces to communicate hazardous events to the driver. The interfaces included a roadside, portable changeable message sign, a smartphone presenting only auditory messages, and a smartphone presenting audio-visual messages. There was significantly better driving performance on key metrics including lane deviation for the in-vehicle message conditions relative to the roadside signs. Furthermore, drivers directed visual attention toward the roadway for the in-vehicle message conditions relative to the roadside sign condition. The results indicate that in-vehicle messaging could provide benefits to primary task performance in driving if the message content is appropriately designed. The findings provide support for a design framework to support in-vehicle communication to drivers approaching work zones and other environments to safely alert them to hazards.

Objective: To assess driving behavior when presented with different work zone features such as signs. Driving behavior upstream of a work zone is of interest since this is the point where drivers need to slow or react to upcoming conflicts such as lane closures, congested traffic, or presence of workers and equipment.Methods: Using 299 time series traces from four-lane roadways with both shoulder and lane closure scenario from the naturalistic driving study, this study analyzed driving behavior by detecting response points within the advance warning area from the first sign to the start of work zone. Response point was defined as the point where drivers reduced speed by a certain threshold. A mixed effect logistic model was developed to assess the relationship between driver response and work zone characteristics.Results: Results indicated the first work zone sign a driver encountered in the immediate area upstream of the work zone was not significantly likely to elicit a driver response. The model found lane ends, speed limit, and active changeable message signs (CMS) as statistically significant. Since more than one sign can be legible to the driver at the same time, the effect of overlapping signs was evaluated, but was not found to have significant effect on the driver response. In general, drivers were more likely to show a response to the signs the closer they got to the start of the work zone. Static work zone speed limit and dynamic speed feedback signs were both found to be more likely to elicit a response as compared to normal speed limit signs (non-work zone related). Drivers who were traveling over the posted speed limit were more likely to show response at any given work zone signs with the exception of the first sign. In addition, driver distraction, and driver information like age, gender, experience and other environmental factors were not found to be significant in the model.Conclusions: Overall, drivers were likely to show a response at the lane ends, work zone speed limit signs, and speed feedback signs.

This paper presents an approach to estimating the operational impacts of freeway work zones. The focus is on significant work zones on freeway corridors as defined by FHWA. The methodology is based on deterministic freeway capacity concepts described in the Highway Capacity Manual and allows the analyst to test impacts of a range of work zone configurations in an extended time–space domain. The focus on extended facilities refers to the analysis of multiple segments of various types, including basic freeway, ramp, and weaving segments. The cost-effective and time-efficient analysis approach can model effects of work zones such as lane closures, lower speed limits, capacity reduction, and the implicit effects of traffic diversion, peak reduction, and other intelligent transportation system strategies. Performance measures include total delay, queuing impacts, average running speed, and the potential to estimate user cost. The methodology focuses on a corridor-based analysis of work zones on freeways. It is not appropriate for network analysis, for long corridors, for signalized arterials, or for cases in which congestion on the arterial network significantly affects freeway operations. In these applications, a simulation-based analysis is more appropriate. However, the methodology presented in this paper is more cost-effective and less data intensive than simulation analysis and can readily be calibrated with local or regional data. This is a key advantage in challenging economic times, when agencies struggle to balance a constrained budget with the need to analyze multiple construction projects within their jurisdiction.

Transportation professionals view the setting of appropriate regulatory speed limits on public roads, including those under repair or reconstruction, as an important tool in promoting safe and efficient operations. The Ohio Department of Transportation sponsored a study to evaluate its work zone speed zoning processes. Researchers observed motorists' speed choices upstream of and adjacent to several combinations of work zone conditions and factors that were used to justify reduced speed limits in Ohio work zones. Researchers also observed motorists' speed choices upstream of and within pilot variable work zone speed zones. Researchers confirmed that motorists reduced their speed only if they clearly perceived a need to do so. Therefore, whenever possible, the first work zone speed limit sign should be installed within view of a work zone condition. In general, the speed reduction downstream of the first nonvariable and variable work zone speed limit signs ranged from 1 to 6 mph and 3 to 11 mph, respectively. In addition, researchers found that the speed reduction on entering a lane shift, within a lane closure, and on entering a median crossover ranged from 4 to 15 mph. On the basis of previous research and the results of the studies documented in this paper, the research team developed work zone speed zone guidelines for multi-lane highways with original posted speed limits greater than or equal to 55 mph. Researchers also made recommendations for where variable work zone speed zoning should be considered.