Control Strategy Optimization for Two-Lane Highway Lane-Closure Work Zones

Pakistan has a population of over 199 million and total road network of approximately 264,400 kilometers that serve about 16.2 million vehicles of all types. According to WHO estimates, there were approximately 30,000 annual Road Crash Fatalities (RCF) in Pakistan in year 2010. Work zone crashes account for significant proportion of all traffic crashes in Pakistan due to higher crash rate as compared to other parts of the highway network. Highway work zone is referred to road area where highway construction, maintenance or activity related to utility maintenance takes place. Workers in highway work zone are exposed to a variety of hazards and face risk of injury and death from construction equipment as well as passing motor vehicles. Safety measures and better understanding of risks involved while moving through the work zone have significant effects on the overall safety climate at work zones. Mismanaged work zone traffic increases the travel time delays, safety issues, vehicle operating costs (VOC) and other associated costs. Performance measures for the work zone traffic management includes user costs (travel time delay, crash cost, VOC), incident response and clearance time, queue length and community complaint. Different work Zone Traffic Management methodologies are being practiced worldwide and extensive research has been carried out at international level on country specific highway work zone safety but in Pakistan very few studies have been carried out on highway work zones. This research aims to critically analyze the impacts of the different Work Zone Traffic Management methods and recommend the best option for Expressways / Motorways in Pakistan. For the purpose of research, the author has selected a section of Motorway (M-2). Two different work zone traffic management methods are being followed in rehabilitation of M-2 .i.e. Parallel / Adjacent Method and Median Cross-Over Method. Performance measures selected for purpose of analysis are Travel Time Delay, Crash Cost (Safety) and VOC and data collected on section of M-2. After critical analysis, it is concluded that Parallel/ Adjacent Method results in lesser Travel Time delay and lesser VOC due to higher operating speeds and thus has higher savings, whereas Median Cross over Methods yield more Crash Cost savings. Keeping in view the driving habits / skills, poor maintenance of vehicles in Pakistan and risk of fatal accidents involved in parallel /adjacent method, median cross over method is preferred.

Speeding in highway work zone: An Evaluation of methods of speed control

In order to evaluate the driving risk of the highway construction and maintenance work zone, identify the dangerous sections and improve the level of road traffic safety, considering the traffic conditions, speed and deceleration were used to evaluate the driving risk by cloud transformation and cloud reasoning technology. Based on the traffic flow theory, the traffic volume, speed and deceleration were chosen as the three evaluation indexes, and determine the certainty degree of evaluation index in the concept of cloud model, and the rule base of driving risk evaluation in highway was established and the risk could be evaluated by this method. The research results quantify the impact of traffic volume, speed and acceleration on the driving risk at the highway construction and maintenance work zone, which provides a good reference value for the future road safety design.

Evaluation of emission level increment in urban and sub urban highway work zones

Law enforcement presence in work zones has long been recognized as one of the most effective speed-reduction methods available to transportation officials. Unfortunately, the design of many work zones makes effective enforcement difficult. Work zones that have no emergency shoulders on either side of the roadway are especially problematic. Incorporating enforcement pullout areas into construction phasing plans has been suggested as a way to improve enforcement activities. However, no guidance had been available on how frequently such enforcement areas should be incorporated. Research was conducted to determine law enforcement and contractor opinions on acceptable spacing criteria for pullout areas in a highway work zone. Two sets of surveys were made by using the Delphi method to solicit the opinions of law enforcement officers and roadway contractors regarding the relative difficulty or effectiveness of pullout areas located at various spacings through a long work zone. The Delphi method was used to quickly bring these groups to consensus. Construction contractors generally were against placing pullout areas closer than 2 mi apart. By contrast, law enforcement officers indicated that at spacing greater than 3 mi, the pullout area would not be useful for traffic enforcement. The results indicate that enforcement pullout areas in work zones should be spaced approximately every 2 to 3 mi or, as an alternative, work zones that eliminate emergency shoulders that are adequate for enforcement purposes should be no longer than 3 mi.

In this study, the traffic parameters were collected from three work zones in Iran in order to evaluate the queue length in the work zones. The work zones were observed at peak and non-peak hours. The results showed that abrupt changes in Freeway Free Speed (FFS) and arrival flow rate caused shockwaves and created a bottleneck in that section of the freeway. In addition, acceleration reduction, abrupt change in the shockwave speed, abrupt change in the arrival flow rate and increase in the percentage of heavy vehicles have led to extreme queue lengths and delay. It has been found that using daily traffic data for scheduling the maintenance and rehabilitation projects could diminish the queue length and delay. Also, by determining the bypass for heavy vehicles, the delay can be significantly reduced; by more than three times. Finally, three models have been presented for estimating the queue length in freeway work zones. Moreover, the procedure shown for creating a queue length model can be used for similar freeways.

Highway work zone safety has been a concern nationwide and will likely draw ever increasing attention as more highway funds are invested in the maintenance of existing highways. To improve work zone safety, the Indiana Department of Transportation (DOT) established a special fund for work zone patrolling, and this study was commissioned to help the Indiana DOT achieve the maximum safety benefits within its budget constraint. With help from the Indiana DOT, a survey of project engineers was conducted to collect work zone information. The findings from the survey were linked with other available data. A random-effect negative binomial model was developed to identify the contributing factors and to estimate crash frequency in highway work zones. The results from the model provided insight for better understanding of crashes in work zones. Various factors, including roadway information, traffic volume, work zone–specific features, and police presence, were identified as things that affect crash frequency in work zones. These and other findings will be used to plan police enforcement activities in future Indiana DOT work zones.

Emphasis on work zone safety and improving the identification of work zone problems has been increased by recent legislation and federal programs. There is a critical need for better data related to highway work zone safety. Results are presented of an investigation to (a) determine what is known about the magnitude of highway work zone crashes, (b) examine characteristics of highway work zone crashes using the Highway Safety Information System, (c) investigate how work zone accidents are reported on police accident report forms and within state accident report systems, (d) identify critical voids in the knowledge of the relative safety of work zones, and (e) examine possible ways to address unfulfilled information needs related to work zone safety. Deficiencies of data reporting practices and issues of data needs pertaining to work zone safety are discussed. Recommendations to improve data collection and fulfill information needs are presented, including suggested data elements to be added to police accident report forms.

Advancing safety in short-term utility work zones: Assessing the role of work zone intrusion alert technologies (WZIATs)

This paper investigated the headway distribution of platooning vehicles in work zones with and without automated Speed Photo Enforcement (SPE). Data from two work zones were collected and analyzed. The portion of vehicles traveling with a very short headway (less than 0.7 sec) was also examined. In addition, the behavior of vehicles near the law enforcement vehicles was analyzed in terms of applying brakes and changing lane in one of the work zones. The results indicated that the mean headway of cars in the median lane significantly increased in both work zones when the SPE van was present compared to the base condition. For trucks, the mean headway increase was significant only in the shoulder lane when the SPE was present. This is a beneficial effect and indicates that drivers had a longer time to react to the lead vehicles. It was also found that the proportion of cars traveling with a very short headway in the median lane significantly decreased when a SPE van was present at one work zone (I-64). In the shoulder lane, no very short headway was observed when SPE was implemented. The difference in braking behavior was not significant when SPE was compared to police car presence. However, lane changing behavior was significantly different for cars traveling in the median lane and also for trucks traveling in the shoulder lane. The proportion of cars changing lanes was 5 percent with a police car present and increased to 8 percent when the SPE van was present. A significant number of trucks changed lanes from the shoulder to the median when the police car was present to comply with state law.

The study examined Measures of Effectiveness (MOE) of vehicle speeds and its comparison with posted speed limits in Advance Warning Zone (AWZ), Working Zone (WZ) and Terminal Transition Zone (TTZ) on NH-8 in India. Results indicate that (1) except slow moving vehicles, all the fast moving vehicles exceeded the posted speed limit of 40 km/h in AWZ and WZ; (2) 85th percentile speeds of Cars/Jeeps, Two-wheelers, Standard Trucks, Mini Trucks, and Buses are much higher than speed limit in AWZ and WZ; (3) mean speeds of fast moving vehicles are more than speed limit in AWZ and WZ; (4) there is no significant difference in the speed of vehicles in AWZ, WZ and TTZ at 95% confidence interval. This study strongly recommends the use of active traffic calming measures like Rumble Strips on Highway Work Zones.

Previous studies have investigated various factors that contribute to the severity of work zone crashes. However, little has been done on the specific effects of light conditions. Using the data from the Enhanced Tennessee Roadway Information Management System (E-TRIMS), crashes that occurred in the Tennessee work zones during 2003–2015 are categorized into three light conditions: daylight, dark-lighted, and dark-not-lighted. One commonly used decision tree method—Classification and Regression Trees (CART)—is adopted to investigate the factors contributing to crash severity in highway work zones under these light conditions. The outcomes from the three decision trees with differing light conditions show significant differences in the ranking and importance of the factors considered in the study, thereby indicating the necessity of examining traffic crashes according to light conditions. By separately considering the crash characteristics under different light conditions, some new findings are obtained from this study. The study shows that an increase in the number of lanes increases the crash severity level in work zones during the day while decreasing the severity at night. Similarly, drugs and alcohol are found to increase the severity level significantly under the dark-not-lighted condition, while they have a limited influence under daylight and dark-lighted conditions.

In highway work zones, lane-changing behaviour near bottlenecks is more urgent than in general segments, referred to as delayed mandatory lane-changing (DMLC). This study proposes an enhanced cellular work zone automata model (DMLC-EWCA) that incorporates DMLC position probability distribution for micro-simulation. Analysing 12 cases from China, the study shows that lane-changing behaviour varies by lane and is influenced by traffic flow and work zone configuration. Extreme value theory is applied to model DMLC position distribution, and lateral lane-changing rules in DMLC-EWCA are improved. The results highlight that traffic flow, speed, and transition area length are key factors influencing vehicle DMLC position. The DMLC-EWCA outperforms the previous CA model at both microscopic and macroscopic levels. A case study applying the DMLC-EWCA optimised transition area length, enhancing innermost lane usage and overall traffic efficiency. The DMLC-EWCA offers a more accurate approach for modelling traffic flow in work zones.

This paper presents the development of a four-regime speed–flow relationship for highway work zones and the effects of police presence (police) and speed photo enforcement (SPE) on the speed–flow relationship and capacity. The base data were collected when signage typical of that shown in the Manual on Uniform Traffic Control Devices for an Interstate highway work zone with no lane reduction was present. Police and SPE data were collected, respectively, when a police patrol car and an SPE van were added to the typical work zone. From each data set, the step-by-step progression from a three-regime model based on least-squares regression to a four-regime speed–flow curve is presented. The four-regime model comprises four equations: (a) horizontal line for free-flow regime that covered the volume levels up to 900 passenger cars per hour per lane, (b) fourth-degree spline for the upper transition part of the speed–flow curve, (c) another fourth-degree spline for the lower transitions part, and (d) equation in the form of power function for the highly congested part of the speed–flow relationship. The speed–flow curve for the base case had a free-flow speed (FFS) of 61.3 mph and a capacity of 1,850 per car per hour per lane (pcphpl). In the police case, however, the FFS and capacity were reduced by 6.3 mph and 50 pcphpl, respectively. For the SPE case, the FFS and capacity were also reduced by 6.8 mph and 100 pcphpl, respectively. The new curves provided the more accurate speed and work zone capacity estimations required for efficient operation.

Highway work zones are associated with significant adverse impacts on safety. Mitigating these impacts can be achieved by implementing several countermeasures. This paper uses controlled experiments in a driving simulator to investigate the effects of physical and digital temporary traffic control countermeasures on work zone safety. These include variable message signs, dynamic speed displays, rumble strips, and lane widths. 116 participants were recruited for the experiment. A linear mixed-effects model was developed to capture the effects of these countermeasures on average travel speed and standard deviation of speeds in the advanced warning area and within the work zone itself. The results reveal that rumble strips installed within the work zone cause the strongest reduction in speeds. Narrower lanes cause smaller speed reductions. In general, the effects of temporary traffic control countermeasures on speeds were local and were not retained beyond their proximity.