Safety Assessment Tool for Construction Zone Work Phasing Plans

The Highway Safety Manual (HSM) is the compilation of national safety research that provides quantitative methods for analyzing highway safety. The HSM presents crash modification functions related to freeway work zone characteristics such as work zone duration and length. These crash modification functions were based on freeway work zones with high traffic volumes in California. When the HSM-referenced model was calibrated for Missouri, the value was 3.78, which is not ideal since it is significantly larger than 1. Therefore, new models were developed in this study using Missouri data to capture geographical, driver behavior, and other factors in the Midwest. Also, new models for expressway and rural two-lane work zones that barely were studied in the literature were developed. A large sample of 20,837 freeway, 8,993 expressway, and 64,476 rural two-lane work zones in Missouri was analyzed to derive 15 work zone crash prediction models. The most appropriate samples of 1,546 freeway, 1,189 expressway, and 6,095 rural two-lane work zones longer than 0.1 mile and with a duration of greater than 10 days were used to make eight, four, and three models, respectively. A challenging question for practitioners is always how to use crash prediction models to make the best estimation of work zone crash count. To solve this problem, a user-friendly software tool was developed in a spreadsheet format to predict work zone crashes based on work zone characteristics. This software selects the best model, estimates the work zone crashes by severity, and converts them to monetary values using standard crash estimates. This study also included a survey of departments of transportation (DOTs), Federal Highway Administration (FHWA) representatives, and contractors to assess the current state of the practice regarding work zone safety. The survey results indicate that many agencies look at work zone safety informally using engineering judgment. Respondents indicated that they would like a tool that could help them to balance work zone safety across projects by looking at crashes and user costs

Calibration of Highway Safety Manual Work Zone Crash Modification Factors

The Highway Safety Manual is the national safety manual that provides quantitative methods for analyzing highway safety. The HSM presents crash modification factors related to work zone characteristics such as work zone duration and length. These crash modification factors were based on high-impact work zones in California. Therefore there was a need to use work zone and safety data from the Midwest to calibrate these crash modification factors for use in the Midwest. Almost 11,000 Missouri freeway work zones were analyzed to derive a representative and stratified sample of 162 work zones. The 162 work zones was more than four times the number of work zones used in the HSM. This dataset was used for modeling and testing crash modification factors applicable to the Midwest. The dataset contained work zones ranging from 0.76 mile to 9.24 miles and with durations from 16 days to 590 days. A combined fatal/injury/non-injury model produced a R2 fit of 0.9079 and a prediction slope of 0.963. The resulting crash modification factors of 1.01 for duration and 0.58 for length were smaller than the values in the HSM. Two practical application examples illustrate the use of the crash modification factors for comparing alternate work zone setups

Maintenance of Traffic for Innovative Geometric Design Work Zones

Currently there are no guidelines within the Manual on Uniform Traffic Control Devices (MUTCD) on construction phasing and maintenance of traffic (MOT) for retrofit construction and maintenance projects involving innovative geometric designs. The research presented in this report addressed this gap in existing knowledge by investigating the state of the practice of construction phasing and MOT for several types of innovative geometric designs including the roundabout, single point urban interchange (SPUI), diverging diamond interchange (DDI), restricted-crossing left turn (RCUT), median U-turn (MUT), and displaced left turn (DLT). This report provides guidelines for transportation practitioners in developing construction phasing and MOT plans for innovative geometric designs. This report includes MOT Phasing Diagrams to assist in the development of MOT strategies for innovative designs. The MOT Phasing Diagrams were developed through a review of literature, survey, interviews with practitioners, and review of plans from innovative geometric design projects. These diagrams are provided as a tool to assist in improving work zone safety and mobility through construction of projects with innovative geometric designs. The aforementioned synthesis of existing knowledge documented existing practices for these types of designs

Evaluation of J-turn Intersection Design Performance in Missouri, Final Report

Research shows that a high percentage of crashes that take place on high-speed rural expressways occur at intersections with minor roads. One low-cost alternative design for improving the safety of at-grade intersections on such expressways is the J-turn. In the last few years, the Missouri Department of Transportation has converted some two-way stop controlled (TWSC) intersections into J-turns. This study evaluated the effectiveness of the J-turn intersection design in Missouri utilizing field studies, a public survey, crash analysis, and traffic conflict analysis. The field studies collected detailed video data at a J-turn site and a control site. The crash analysis included a statistically rigorous empirical Bayes before-after safety evaluation of five J-turn sites in Missouri. The J-turn design resulted in a 34.8% reduction in crash frequency for all crashes and a 53.7% reduction in crash frequency for all injury and fatal crashes. Both reductions were significant at the 95% confidence level. Annual disabling injury crashes and minor injury crashes decreased by 86% and 50%, respectively. None of the five sites exhibited a fatal crash following J-turn implementation. This five-site analysis showed that annual right angle crashes decreased from 6.3 to 1.3, a 80% reduction. One of the most severe crash types, the left turn, right angle crash, was completely eliminated by the J-turn. One conflict measure, average time to collision, was found to be four times higher at the J-turn site compared to the control TWSC site among minor road turning vehicles, indicating greater safety at the J-turn site. The average wait time at the J-turn site was half the wait time at the control site, while the average travel time at the J-turn site was approximately one minute greater than at the TWSC site. When the public was surveyed regarding trip time perceptions resulting from the J-turn, the majority said there was no adverse effect. A high percentage of minor road left turning and through movements at the J-turn site merged into the travel lanes within the first 400 feet of the acceleration lane. Public opinion regarding the J-turn at US 63 and Deer Park Rd was mixed. Frequent concerns raised by respondents included difficulty merging following the U-turn, improper use of acceleration and deceleration lanes, insufficient U-turn radius to accommodate large vehicles, and driver confusion

Investigation of Alternative Work Zone Merging Sign Configurations

This study investigated the effect of an alternative merge sign configuration within a freeway work zone. In this alternative configuration, the graphical lane closed sign from the MUTCD was compared with a MERGE/arrow sign on one side and a RIGHT LANE CLOSED sign on the other side. The study measured driver behavior characteristics including speeds and open lane occupancies. The measurements were taken at two identical work zones on I-70 in Missouri, one with the new test sign and the other with the standard MUTCD sign. The study found that the open lane occupancy upstream of the merge sign was higher for the test sign in comparison to the MUTCD sign. Occupancy values at different distances between the merge sign and the taper were similar for both signs. The test sign had 11% more traffic in the open lane upstream of the merge sign. In terms of safety, it is desirable for vehicles to occupy the open lane as far upstream from the taper as possible to avoid conflicts due to the lane drop. Thus, the test sign proved to be a good alternative to the MUTCD sign. The analysis of speed characteristics did not reveal substantial differences between the two sign configurations. The 85th percentile speeds with the MUTCD sign were 1 mph and 2 mph lower than the test sign at the merge sign and taper locations, respectively

Thoughts on the future of artificial intelligence and transportation

In this concluding chapter of the Circular, we have asked members of our committee to share with the readers their personal thoughts on the future of AI and transportation. We are pleased herein to present select quotes from the committee members, organized alphabetically, on that topic

Work Zone Speed Limits and Motorist Compliance: Tech Transfer Summary

This study sought to identify best practices for setting work zone speed limits by state departments of transportation (DOTs) and to evaluate select strategies for improving compliance with work zone speed limits. The objectives of this project were achieved by synthesizing information from a literature review, a state DOT survey, and field evaluations of select speed management strategies

Work Zone Speed Limits and Motorist Compliance

This study sought to identify best practices for setting work zone speed limits by state departments of transportation (DOTs) and to evaluate select strategies for improving compliance with work zone speed limits. This was achieved by synthesizing information from a literature review, a state DOT survey, and field evaluations of select speed management strategies. The state DOT survey found that work zone speed limits are typically established based on the characteristics and conditions of the site, including permanent speed limit, facility type, worker presence, positive protection, work duration, and type and location of work activity. Work zone speed limit reductions of 10 mph are most frequently utilized on high-speed facility types, with further reductions provided based on worker presence in the absence of positive protection (e.g., concrete barrier). While the 10 mph speed limit reduction is often viewed as effective, the use of a 45 mph work zone speed limit when workers are present may require the use of additional speed reduction countermeasures to be effective. Research studies have generally shown several types of work zone speed management strategies, such as speed display signs, law enforcement, variable (dynamic) speed limits, temporary rumble strips, and portable changeable message sign (PCMS) messages, to be effective in reducing vehicle speeds in work zones. The work zone speed management strategies most frequently implemented by state DOTs include higher fines for speeding in work zones and lights on contractor or maintenance vehicles. While DOTs generally view law enforcement with an officer present as the most effective strategy for managing work zone speeds, they also perceive the availability of law enforcement as the greatest challenge to managing work zone speeds, followed by driver indifference and distracted drivers. Based on the findings from the literature review and DOT survey, a field study was performed to assess the effectiveness of two work zone speed management strategies, which included a speed feedback trailer (SFT) and law enforcement. In general, the magnitude of the speed reduction effects were greatest in the general proximity of the SFT. A second field evaluation assessed the effectiveness of a specialized work zone enforcement strategy. The visible presence of law enforcement activities at this location reduced work zone speeds by approximately 5 to 7 mph

AMR Leader-Follower System TMA Evaluation

MoDOT project # TR202119aTo reduce worker injuries in truck mounted attenuator (TMA) crashes, the Missouri Department of Transportation (MoDOT) is piloting a Leader-Follower TMA system, which allows the worker to be removed from the follower vehicle, in two districts. The objectives of this research study are to evaluate MoDOT\u2019s pilot program for Leader-Follower TMAs in two districts, to synthesize practices of other state Departments of Transportation (DOTs) regarding Leader-Follower TMAs, and to identify obstacles to implementation faced by other state DOTs. The research methodology to meet this objective includes a literature review, DOT survey and interviews, field study, interviews with MoDOT personnel, and economic analysis. Results from field evaluations conducted in this research study and other prior research studies generally show that the system performs as expected, with some challenges related to GPS-denied environment, tight turns, and path deviations. Based on the survey results, four agencies have implemented Leader-Follower TMA systems, 19 agencies are exploring or have previously explored them, and 20 agencies are not exploring their potential use. Overall, the study findings indicate that the Leader-Follower TMA has the potential to be an effective tool in improving safety for workers in mobile work zones. A benefit-cost-ratio (BCR) of 0.83 was calculated in this research study. There is potential for the BCR to increase in the future as costs will likely decrease due to economies of scale. Challenges to implementation are both technical (e.g., GPS signal loss, need for situational awareness of hills and curves, need for performance data, and need for procedures to reset the system when there is no driver in follower vehicle) and non-technical (e.g., legislation, procurement, competing priorities, and lack of awareness of the system and its capabilities). Potential enhancements to help address some of the technical challenges include a supplementary guidance system for loss of GPS signal, a remote reset feature, additional cameras, and a remote alarm trigger

Effectiveness of Speed Management Methods in Work Zones

MoDOT project # TR202115Management of speeds is a significant component of any strategy to reduce work zone crashes. The objective of this study is to investigate the effectiveness of speed management countermeasures, such as speed display trailer, speed display trailer with red and blue lights, work vehicle with red and blue lights, and active and passive law enforcement, in managing vehicle speeds in work zones. The research methodology includes a review of the existing literature, field study, simulator study, and driver survey. The field study was conducted at a work zone on I-270 in the St. Louis region. All speed countermeasures tested in the field study achieved speed reductions. Active law enforcement was the most effective speed countermeasure for both daytime and nighttime conditions. Thirteen scenarios were studied using a driving simulator. Combining a speed display trailer and active law enforcement was the most effective countermeasure for daytime conditions. Using a speed display trailer by itself was the most effective for nighttime conditions. While respondents to both the driver and post-simulator surveys generally preferred the speed display trailer, they also admitted that the presence of law enforcement would be the most effective in causing them to slow down. Overall, the results of the study indicate that any of the tested countermeasures would help reduce speeds in a work zone. In some instances, deploying multiple countermeasures at the same site was found to be the most effective speed reduction strategy