Wrong-way Driving Countermeasures Research Articles

Leveraging text mining approach to explore research roadmap and future direction of wrong-way driving crash studies

This study delves into the wrong-way driving (WWD) research performed in the United States over the past five decades. The study employs a text network to summarize and synthesize major themes, data sources, and collaboration efforts from 123 previously published WWD articles collected from various online databases. The analysis shows that the majority of WWD studies were conducted between 2014 and 2020. Throughout the entire period, the primary focuses have been on WWD countermeasures, freeways, exit ramps, contributing factors, driver behavior, and detection systems. Over time, there has been a noticeable shift in the key themes, whereby earlier studies focused on freeways and driver behaviors, while the latter delved into exit ramps, limited access, and contributing factors among others. Most studies were from Florida, Texas, Illinois, and Alabama, with little collaboration of researchers across the States, except for Alabama and Illinois. Further, across the four States, there observed variations in the interests. Studies from Texas and Florida were centered on WWD countermeasures, detection systems, and the use of connected vehicles, while Illinois and Alabama investigated WWD crashes on exit ramps and interchanges. Despite the development and deployment of various countermeasures, there is still a need to develop crash modification factors to examine the effectiveness of the countermeasures. Furthermore, as technology continues to advance, connected and autonomous technology is expected to play a significant role in mitigating the WWD problem. The findings are essential for transportation agencies to evaluate the mitigation efforts and direct resources toward the right course of action.

Identification of high-risk roadway segments for wrong-way driving crash using rare event modeling and data augmentation techniques

Wrong-Way Driving (WWD) crashes are relatively rare but more likely to produce fatalities and severe injuries than other crashes. WWD crash segment prediction task is challenging due to its rare nature, and very few roadway segments experience WWD events. WWD crashes involve complex interactions among roadway geometry, vehicle, environment, and drivers, and the effect of these complex interactions is not always observable and measurable. This study applied two advanced Machine Learning (ML) models to overcome the imbalanced dataset problem and identified local and global factors contributing to WWD crash segments. Five years (2015–2019) of WWD crash data from Florida state were used in this study for WWD model development. The first modeling approach applied four different hybrid data augmentation techniques to the training dataset before applying the XGBoost classification algorithm. In the second model, a rare event modeling approach using the Autoencoder-based anomaly detection method was applied to the original data to identify WWD roadway segments. A third model was applied based on the statistical method to compare the performance of ML models in predicting the WWD segments. The performance comparison of the adopted models showed that the XGBoost model with the Adaptive Synthetic Sampling (ADASYN) method performed best in terms of precision and recall values compared to the autoencoder-based anomaly detection method. The best-performing model was used for the feature analysis with an interpretable machine-learning technique. The SHapley Additive exPlanations (SHAP) values showed that high-intensity developed land use, length of roadway, log of Annual Average Daily traffic (AADT), and lane width were positively associated with WWD roadway segments. The results of this study can be used to deploy WWD countermeasures effectively.

Statewide Application of Wrong-Way Driving Crash Risk Modeling and Countermeasures Optimization Algorithm to Identify Optimal Locations for Countermeasure Deployment on Florida Limited Access Facilities

Wrong-way driving (WWD) crashes can have significant impacts on freeway safety and operations. Deploying intelligent transportation systems (ITS) WWD countermeasures at freeway exit ramps can effectively reduce WWD crash risk (WWCR), but these countermeasures are expensive. In this paper, a WWCR segment model and WWD countermeasures optimization algorithm are developed for all Florida limited access facilities (56 roadways with 1,375 exits) to identify the optimal locations for ITS countermeasure deployment. These were previously developed for specific toll-road networks within Florida, but never for a statewide network. Multiple WWCR models were investigated, with the final Poisson model using four-exit segments and 5 years of WWD event data. This model showed that more WWD events and higher crossing road traffic volumes increased WWCR, while certain interchange designs increased or decreased WWCR. Sixty-three segments containing 169 exit ramps without ITS WWD countermeasures were identified as WWD hotspots; these ramps were compared with the 169 ramps with the highest WWCR selected by the optimization algorithm. The algorithm selected 96 ramps not in the hotspots (improved resource utilization of 56.8%) and provided a 38.6% increase in WWCR reduction. Comparing WWD detection and turnaround data from 31 sites with rectangular flashing beacon ITS countermeasures to the optimization indicated a significant positive association between WWCR and turnaround percentage (higher WWCR at sites with lower turnaround percentage), verifying the accuracy of the optimization. By showing the transferability, scalability, accuracy, and benefits of this approach, this paper can help agencies reduce WWD and improve freeway safety and operations.

Estimating Fatality and Injury Savings Because of Deployment of Advanced Wrong-Way Driving Countermeasures on a Toll Road Network

Limited access facility wrong-way driving (WWD) crashes are typically more severe than other crashes. Deploying advanced WWD countermeasures, such as rectangular flashing beacon (RFB) and light-emitting diode (LED) technologies, at exit ramps can reduce WWD crashes, injuries, and fatalities. No previous research has developed a methodology to quantify the potential fatality and injury savings because of future countermeasure deployments. This paper developed such a methodology and applied it to Florida’s Turnpike Enterprise (FTE) toll road network. From 2011–2016, there were 53 FTE WWD crashes, resulting in 16 fatalities and annual injury costs of $37 million. The proportion of these crashes occurring during night-time was 87%. RFB and LED life-cycle injury savings and costs were determined for all 216 FTE exits. The total savings were $424 million for RFBs (benefit–cost [B/C] ratio of 23.20) and $144 million for LEDs (B/C ratio of 13.13). Deploying countermeasures at the 103 exits with the highest B/C ratios would provide 70% of the total possible savings by equipping 40% of the ramps. For the same capital investment, RFBs provide more savings than LEDs. Spending $1 million to deploy RFBs will provide similar savings as spending $3.4 million to deploy LEDs. Evaluating the existing FTE RFB and LED ramps shows that RFBs are more effective at night-time and can provide three times the savings of LEDs. The results of this paper show the improved performance of RFBs over LEDs and provide an example that other agencies could follow to identify savings and cost-effectively deploy advanced WWD countermeasures.

Benefit–Cost Analyses of Rectangular Flashing Beacon Wrong-Way Driving Countermeasures on Toll Road Exit Ramps in Florida

In recent years, rectangular flashing beacons (RFBs) and other technologies have been used as wrong-way driving (WWD) countermeasures on limited access facilities. Studies have shown that these devices effectively reduce WWD, but no research has compared the financial benefits and costs of these countermeasures. Three different methodologies were used to conduct benefit–cost analyses for RFB WWD countermeasures installed on Central Florida toll road exit ramps. The studied benefits included savings from reductions in WWD crashes, non-crash events, and injuries, whereas costs included equipment, installation, and maintenance costs. For the first two methodologies, the reduction in WWD crash risk (WWCR) at the RFB-equipped ramps was determined. This WWCR considered non-crash WWD events, interchange design, and traffic volumes. Different measures of effectiveness (turn-around percentage of detected wrong-way vehicles at the RFB ramps and reduction in WWD 911 calls and citations at the RFB interchanges compared with similar comparison interchanges without RFBs) were used in these two methodologies to estimate the WWCR reduction and associated savings. For the third methodology, the relationship between WWD crashes and non-crash events was used to determine the average savings for WWD 911 calls and citations. Before–after analyses were then conducted to determine the individual reductions in WWD 911 calls and citations. Applying these three methods resulted in life-cycle benefit–cost ratios ranging from 2.49 to 4.10 (crash savings) and from 4.77 to 7.20 (injury savings). Other agencies could use these methodologies to determine the benefits of WWD countermeasures or other technologies with limited crash data.

An optimization approach for deployment of intelligent transportation systems wrong-way driving countermeasures

The nature of wrong-way driving (WWD) crashes on limited access facilities makes it difficult for agencies to combat them effectively. WWD countermeasures equipped with Intelligent Transportation Systems (ITS) technologies, such as warning lights and detection devices, have been proven to reduce WWD. However, agencies often cannot deploy these ITS countermeasures at all exit ramps due to their expense. This paper discusses an innovative WWD countermeasure optimization approach to help agencies identify the optimal deployment locations based on available resources. The approach consists of a WWD crash risk (WWCR) model and a WWD countermeasures optimization algorithm. The WWCR model uses non-crash WWD events, interchange designs, and traffic volumes to predict the number of WWD crashes on multi-exit segments of limited access facilities. Then, the optimization algorithm uses the model results to identify the best exits for ITS countermeasure deployment based on WWCR reduction, available resources, and other applicable constraints. This approach was applied to the Florida’s Turnpike Enterprise (FTE) toll road network. Twenty-four segments were identified as WWD hotspots due to high WWCR. Three different optimization scenarios were tested to show how different constraints affect the results. These scenarios resulted in 38% to 41% of the maximum possible WWCR reduction by equipping only 39 of the 196 FTE ramps (20%) and could help FTE better utilize its investment by 36% compared to only equipping ramps in the identified 24 WWD hotspots. Other agencies could personalize this approach based on their available resources, and preferred WWD countermeasures to achieve similar benefits.

Comparison of two intelligent transportation systems Wrong-Way driving countermeasures currently deployed on Florida toll roads

Wrong way driving (WWD) crashes on high-speed limited access facilities often cause severe injuries and deaths. Conventional “Wrong Way” signs can reduce WWD events but can be insufficient in some cases. Intelligent Transportation Systems (ITS) WWD countermeasures can more effectively notify wrong-way drivers of their mistake. This paper compares the safety performance of two types of ITS WWD countermeasures implemented in Florida: Light-Emitting Diode (LED) signs in South Florida (which include one set of signs and one camera) and Rectangular Flashing Beacon (RFB) signs in Central Florida (which include two sets of signs and three cameras). The reduction in WWD events (911 calls and citations) and the percentage of wrong-way drivers who self-corrected their WWD behavior were used as surrogate safety performance measures instead of crashes, since WWD crashes are rare. Chi-squared tests revealed a significant reduction in WWD events at the LED and RFB treated sites compared to control sites without these countermeasures. Comparison group analyses indicated that the LED and RFB countermeasures reduced WWD events by 48.1% and 69.4%, respectively. Additionally, photographs taken by cameras on the countermeasures and/or closed-circuit television cameras monitored by the traffic management centers showed that over 16% of the 72 detected wrong-way vehicles self-corrected at the LED sites and 81% of the 353 detected wrong-way vehicles self-corrected at the RFB sites. The methods and results in this paper can help transportation agencies throughout the United States identify the most suitable WWD countermeasures and evaluate their performance.

Characteristics of Law Enforcement Response to Wrong-Way Driving Events in Florida

Wrong-way driving (WWD) can result in severe crashes. By responding quickly to WWD dispatch calls, law enforcement officers (LEOs) could stop the wrong-way vehicle before a crash occurs. This paper analyzed law enforcement (LE) response times to WWD dispatch calls in Florida between January 2003 and April 2018 to determine significant effects. The average LE response time was much lower for 2013 onward than before 2013. Average response time was lower during nighttime and in urban areas and was higher for county roads and toll roads. Two ordinal logit models were also developed. These models found that dispatch calls closer to regional traffic management centers or rest areas, in urban areas, or on state roads or local roads typically had lower response times than calls not in these locations. In addition, WWD dispatch calls on toll roads had lower response times than calls on non-toll limited access facilities. Intelligent transportation system (ITS) WWD countermeasures with flashing signs, detection devices, cameras, and direct communication with traffic management centers also help LEOs respond quickly to detected WWD events and more accurately identify the vehicle’s location. As of June 2018, these technologies located at 70 toll road exit ramps in Florida have prompted 307 wrong-way drivers to turn around, possibly preventing nine crashes and saving LEOs over 116 h. The results of this research can help identify locations where increasing LEO presence or installing ITS WWD countermeasure technologies could help reduce WWD response time and WWD crashes, potentially saving lives.

Closed-Course Study to Assess the Conspicuity of Wrong-Way Driving Countermeasures

Alcohol has been found to be the primary contributing factor in many wrong-way crash studies. Thus, Texas A&M Transportation Institute researchers conducted a night-time closed-course study to assess the conspicuity of select signing and pavement marking wrong-way driving countermeasures from the perspective of alcohol-impaired drivers. Lowering the sign height, making the sign larger (i.e., oversized), adding red retroreflective material to the sign support, or adding flashing red light-emitting diodes around the border of the sign did not improve the ability of the alcohol-impaired drivers to locate WRONG WAY signs in a search task. However, in post-task assessments it was the opinion of the participants that the oversized sign, red retroreflective material, and flashing lights made it easier to find the WRONG WAY sign. The participants also thought that these three countermeasures caught their attention more than the standard size WRONG WAY sign mounted at 7 ft. Researchers did not find a significant difference in the recognition time between standard and modified wrong-way arrow marking designs. The modified arrow had a narrower head that provided equivalent recognition while potentially reducing maintenance costs. The participants also similarly assessed the ease at which they could find the two arrow designs among the other markings. Thus, it appears that the modified design performed as well as the current design. Researchers recommend implementing the modified wrong-way arrow design as existing wrong-way arrows are replaced.

A Wrong-Way Driving Crash Risk Reduction Approach for Cost-Effective Installation of Advanced Technology Wrong-Way Driving Countermeasures

Wrong-way driving (WWD) is hazardous on high-speed limited access facilities. Traditional signage and pavement markings will not always prevent intoxicated or confused drivers from entering these facilities the wrong way. To better alert wrong-way drivers, agencies can consider WWD countermeasures equipped with advanced technologies (including warning lights and detection devices) on exit ramps. However, these countermeasures can be expensive for agencies to install on entire roadways or corridors. This paper develops an innovative WWD crash risk (WWCR) reduction approach consisting of a WWCR segment model and an optimization algorithm that can be used to help agencies decide where to install WWD countermeasures. The approach examines segments of limited access facilities to determine the interchanges where advanced technology WWD countermeasures will provide the greatest reduction in WWCR based on an agency’s available resources. A hypothetical example application of this approach is shown for the Central Florida Expressway Authority toll road network. This example shows how the WWCR reduction approach can help agencies identify the optimal investment level and high-risk locations. It also shows how the optimization algorithm can provide significant cost savings compared with equipping entire roadway segments (57% savings) or corridors (83% savings). Agencies can customize the algorithm by adding constraints to represent various scenarios and make the algorithm applicable for networks ranging from single roadways to statewide systems. This WWCR reduction approach could be utilized by agencies nationwide to help them save resources and prioritize investment.

Evaluating Wrong-Way Driving Characteristics, Countermeasures, and Alert Dissemination Methods through Driver and Law Enforcement Surveys

Wrong-way driving (WWD) on limited-access highways is a serious driver error that could be fatal for both the wrong-way driver and right-way drivers. Agencies and law enforcement officers (LEOs) can spend valuable time and resources responding to WWD events. A survey of 247 LEOs found that despite being dispatched multiple times per year in response to WWD, most issue fewer than one WWD citation per year. In the survey, LEOs also gave their perspectives on the characteristics of WWD events and the influences behind WWD. Agencies typically use dynamic message signs (DMS) for notifying right-way drivers of WWD events, but little research has considered solutions that are less costly and potentially farther-reaching. A survey of 900 Florida toll-road drivers found that drivers rely on navigation devices, apps, or both, significantly more than DMS for traveler information. Drivers were receptive to receiving WWD alerts through navigation services and indicated that they would react to WWD events in a way that is beneficial to highway safety. Crowdsourcing technologies were considered to generate WWD information and quickly disseminate alerts to drivers and officers. Additional survey questions answered by a combined group of 2,052 drivers, LEOs, and agency officials determined that among advanced WWD countermeasures, most preferred two sets of “Wrong Way” signs equipped with rectangular flashing beacons over one set of signs with light emitting diodes. Combining advanced countermeasures with innovative right-way driver notification methods could enhance law enforcement efficiency, reduce WWD crashes, and provide safer conditions for both drivers and officers.

Analysis of Performance Data Collected from Two Wrong-Way Driving Advanced Technology Countermeasures and Results of Countermeasures Stakeholder Surveys

Wrong-way driving (WWD) often leads to severe collisions that cause serious injuries and deaths. Conventional “Wrong Way” signs can reduce WWD events, but can be insufficient in some cases. In areas with many WWD events, transportation agencies can be proactive by considering the use of countermeasures with advanced technologies to actively warn motorists of WWD violations. This paper analyzes recent performance data collected from two types of advanced technology WWD countermeasures implemented in Florida: light-emitting diode (LED) signs in South Florida and rectangular flashing beacon (RFB) signs in Central Florida. The 17 LED sites experienced a 38% reduction in WWD citations and 911 calls after the signs were installed. Images taken by the on-site cameras were examined to see how many vehicles turned around for both the RFB and LED treatment sites. Over 77% of the 170-detected wrong-way vehicles self-corrected their wrong-way movement at the RFB sites (each with two sets of signs and multiple cameras) and 14% self-corrected at the LED sites (each with one set of signs and one camera). Surveys were also conducted regarding these two WWD countermeasures. More than 73% of the 2,052 respondents preferred RFBs over LEDs, mainly due to the double set of RFB signs and their flashing pattern. The performance and survey results show that both the LEDs and RFBs have effectively reduced WWD movements. However, modifications could be made to both countermeasures to improve their detection ability and make wrong-way drivers more likely to turn around.

Assessment of countermeasure effectiveness and informativeness in mitigating wrong-way entries onto limited-access facilities

Wrong-way crashes are a major cause for safety concerns along freeways and limited-access facilities. Although wrong-way crashes account for a relatively small portion of total crashes, the impact between two cars crashing into each other at high speeds in opposite directions often results in severe injuries or fatalities compared to any other type of crash. To seek solutions for mitigating wrong-way driving (WWD), multiple field tests involving a number of countermeasures using Intelligent Transportation Systems (ITS) technologies have been conducted in Florida. This study was aimed to evaluate these WWD countermeasures in Florida and develop recommendations regarding the most effective and informing WWD countermeasures through (1) analysis of existing data and studies, (2) field WWD testing using focus groups, (3) a public opinion survey, and (4) capturing human factors elements using simulation via a driving simulator. The results proved that red Rectangular Rapid Flashing Beacons (RRFBs) are the top countermeasure for mitigating WWD at freeway off-ramps, with wigwag flashing beacons as the second best, and detection-triggered blank-out signs and detection-triggered LED lights around “WRONG WAY” signs (tie) as third best. Red flush-mount Internally Illuminated Raised Pavement Markers (IIRPMs) were found to be statistically significantly effective for possible consideration as a supplemental countermeasure for mitigating WWD at freeway off-ramps. The countermeasure of delineators along off-ramps was found to be the least effective and was not considered for recommendation for deterring WWD at freeway off-ramps. This study further confirms that the newly-developed signing and pavement marking standards in Florida are a positive countermeasure on arterials to mitigate wrong-way entries onto freeway off-ramps.

Identifying Wrong-Way Driving Hotspots by Modeling Crash Risk and Assessing Duration of Wrong-Way Driving Events

Because wrong-way driving (WWD) crashes are often severe, it is important for transportation agencies to identify WWD hotspot segments appropriate for potential implementation of advanced WWD countermeasures. Two approaches to identify these hotspot segments were developed and applied to a case study of limited-access highways in Central Florida. The first approach used a Poisson regression model that predicted the number of WWD crashes in a roadway segment based on WWD citations, 911 calls, traffic volumes, and interchange designs. Combining this predicted crash value with the actual number of WWD crashes in the segment gave the WWD crash risk of the segment. Ranking roadway segments by WWD crash risk provided agencies with an understanding of which segments had high WWD crash frequencies and high potential for future WWD crashes. This approach was previously applied to South Florida; the research presented here extended this approach to Central Florida. The second approach was based on operational data collected in traffic management centers and could be used if accurate WWD 911 and citation data with GPS location were not available or as a supplement to the first approach. The approach identified and ranked WWD hotspots on the basis of the reported duration of WWD events. In Central Florida, the results of the two approaches agreed with each other and were used by agencies to decide where to implement advanced WWD countermeasures. Together, these approaches can help transportation agencies determine regional WWD hotspots and cooperate to implement advanced WWD countermeasures at these locations.

The odds of wrong-way crashes and resulting fatalities: A comprehensive analysis

The United States of America and other nations are grappling with the incidence of wrong-way driving (WWD). The issue is as important today (NTSB, 2012) as it was a half-century ago (Hulbert and Beers, 1966). In the absence of a comprehensive analysis, any effort to implement WWD countermeasures can be counterproductive. Hence, this effort began with the express intent to identify the factors that cause WWD crashes and fatalities. This work is sizeable in that it evaluated one million complete crash records from Florida. The methodology comprised (a) administering a survey on the perceptions about WWD; (b) developing binomial logistic models for computing the odds of WWD crashes, and of fatal crashes within the WWD space; (c) analyzing the contributing variables; and (d) comparing perceptions with crash analysis results. The study parameters included driver's age, gender, licensing state, physical defect, blood alcohol concentration, vehicle use, seatbelt compliance, day and time of crash, roadway lighting, facility type, weather conditions, road geometrics, and traffic volumes. Individual variable analysis of 23 parameters and the model development process included the determination of odds ratios and statistical tests for the predictive power and goodness-of-fit. The results of this work are generally consistent with expectation, yet surprising at times. This work concludes with decision-making inputs to the scientist, policy-maker and practitioner on the need for effectively engineering the roads, actively educating people about wrong-way driving, and strictly enforcing traffic laws, rules and regulations.

Addressing wrong-way driving as a matter of policy: The Florida Experience

Wrong-way driving (WWD) incidents garner considerable interest from the media, elected representatives, and policy makers. Almost a half-century after Hulbert and Beers (1966), the National Transportation Safety Board and others continue to research WWD countermeasures. The recent increase in WWD re-kindled a national discussion in the United States of America, and is bringing about a significant change in the approach to addressing this crash type. The main purpose of this work is to present a policy-oriented framework toward addressing WWDs in a systematic manner and to suggest a systemic discipline for transforming policy objectives to actionable outcomes. To accomplish this goal, the leadership of the Florida Department of Transportation played a pivotal role in converting strategy to reality by promoting organizational linkages and active collaboration. The method included: (a) implementing pilot projects; (b) conducting a statewide study with crash evaluation and field reviews, identifying interchange types, and developing countermeasures; (c) evaluating and deploying experimental devices specifically approved by the Federal Highway Administration; (d) conceptualizing a human factors study; (e) transforming recommendations to design guidance; (f) discussing with planners on interchange types susceptible to WWDs; (g) retrofitting exit ramps with the recommended countermeasures; and (h) leveraging the media to promote awareness and to educate the public about the dangers of driving under the influence. The result of this policy push is that, from an engineering view point, design changes were made; from an education perspective, WWD awareness was prioritized; and from an enforcement angle, the Florida Highway Patrol proactively detects and addresses WWD crashes.

Wrong-Way Driving Prevention

Wrong-way driving (WWD) crashes are rare on Central Florida roadways. However, WWD is a severe hazard, especially on high-speed limited access roadways. This research developed the first driver survey to obtain details about unreported WWD events on Central Florida toll roads and freeways. This phone survey asked participants about WWD events witnessed either by the participant or by a family member, friend, or acquaintance. The 400 completed surveys showed that State Road 408 (SR-408) and Florida's turnpike (SR-91) experienced the most WWD events. Fourteen percent of the WWD events resulted in a crash, and only 10% of the WWD events witnessed by participants were reported to law enforcement or roadway agencies, even though 50% of the events caused the survey participants to feel a high risk of danger. These results show that WWD is more frequent than indicated by crashes or 911 calls. On the basis of these results, the Central Florida Expressway Authority (formerly known as the Orlando–Orange County Expressway Authority) is pilot testing and evaluating the use of rapid rectangular flashing beacons (RRFBs) as a WWD countermeasure. This test will be the first use of RRFBs to combat WWD. Elsewhere, Florida's Turnpike Enterprise is installing flashing “Wrong Way” signs along the Homestead Extension (SR-821) and Sawgrass Expressway (SR-869) in South Florida, and the Florida Department of Transportation is implementing a variety of WWD countermeasures at I-10 ramps in Tallahassee in North Florida.

Wrong-Way Driving

Wrong-way driving (WWD) is one of the most dangerous driver errors or behaviors on limited access facilities. Previous studies focused on analyzing WWD crashes but discovered that WWD crashes were extremely rare. Using WWD 911 calls and WWD citations, which occur much more frequently than WWD crashes, to help predict WWD risk allows roadway agencies to be proactive and implement WWD countermeasures at problem areas instead of waiting for serious WWD crashes to occur. This study developed a model to determine WWD risk according to WWD crashes, citations, and 911 calls. For the development of this novel model, a market basket analysis was used to determine the overlap between the three WWD data sets (crashes, 911 calls, and citations for the years 2011 and 2012 on Florida Interstates and toll roads). The independent WWD events were then used to develop a generalized Poisson regression model that allowed the WWD 911 calls, citations, and crash frequencies to be converted to WWD risk values. WWD risk densities were also calculated by using either vehicle miles traveled or roadway length to consider exposure. The counties and roadways were then ranked with respect to WWD risk values and densities; these rankings indicated that Miami–Dade was a problematic county because it was ranked highest by WWD risk value and its nine Interstates or toll roads were ranked in the top 15 by WWD risk density. The developed model and macroscopic rankings are very useful to help identify counties and roadways where WWD countermeasures should be implemented.