For nearly 100 years the design of highways has incorporated safety through the application of criteria to each individual design element. Design elements are items like the horizontal curve, vertical curves, the cross-section, clear zone and roadside slopes. As a result, safety is only indirectly addressed since the design elements are developed in isolation without a good understanding on the impact of one element on another. To make matters worse, design elements communicate messages to the driver about the appropriate speed for the highway. Long straight tangent sections encourage drivers to drive faster whereas curved highway segments communicate a lower operating speed. This can lead to inconsistent message to the driver when design elements are not coordinated with each other. A new method is proposed that accounts for the interaction between design elements in such a way that the designer can estimate the frequency and societal cost of motor vehicle crashes. With this estimate of cost, the designer can base design decisions on what would minimize the societal cost of both the infrastructure improvement and safety. This method will allow designers to formulate highway designs that achieve a specific level of safety and communicate consistent information to drivers. This research provides a valuable planning and design tool for practitioners and policy makers alike. It represents an important shift in the highway design paradigm.

The objective of this research is to develop a new and efficient method of absorbing a vehicle??s kinetic energy for highway safety crash cushions. A vehicle that makes a direct impact with a rigid highway structure traveling at highway speeds can be fatal for its occupants. Crash cushions are implemented on roadways in front of these rigid structures with the intent to ??soften?? the impact. The cushion will bring a vehicle to a stop at safe rates before it impacts the rigid structure. The energy absorbing component of the crash cushion must meet four main requirements. The cushion must reduce the vehicles speed at a rate that does not allow the occupant to impact the vehicle interior at velocities greater than 12 m/s. The cushion must then bring the vehicle to a complete stop with deceleration rates below 20 g??s. A crash cushion must satisfy these requirements for an 820 kg vehicle and a 2000 kg vehicle traveling at 100 km/hr. Advanced design methodologies were applied to enable multiple, innovative design concepts. These concepts made use of the deformation of steel in structural pipe, structural angle, and structural plate to reduce the velocity of a vehicle at a safe rate. Critical design parameters were identified which allowed for efficient and effective numerical experiments to be conducted. The data collected from these experiments were then validated when compared to physical test data. After the data had been collected, each of the designs was compared to one another in order to decide upon the best design. The design selected was the deforming plate concept which makes use of steel plate mounted in a fashion that created two arms that acted similar to two cantilever beams. A wedge was forced beneath these arms deforming them upward. This design is effective because the deformation can be easily controlled by the thickness of the plate, the moment arm created by the wedge, and the geometry of the wedge. Steel plate is a readily available material that requires minimal manufacturing for installation preparation making it cost-effective, and easy to install. In the event of impact with the cushion, new parts will be inexpensive and readily available. Being reusable, easy to repair and low in cost, the energy absorbing concept presented herein is a cost effective alternative to existing energy absorbing technology. Due to replaceable parts being readily available, repair time and cost will be reduced compared to other designs that require new parts to be fabricated for replacement. This will make for a competitive design.

Driving the wrong way on freeways has been a nagging traffic safety problem since the interstate highway system was founded in the 1950s. Despite four decades of highway striping and sign improvements at freeway interchanges, the problem persists. This paper is to determine the contributing factors to wrong-way driving on freeways and to develop promising, cost-conscious countermeasures to reduce this driving errors and related crashes. Wrong-way crash data from Illinois Department of Transportation (IDOT) crash database were collected with 632 possible wrong-way crashes. The real wrong-way crashes were further identified by reviewing the wrong-way crash reports hardcopies and information from other resources. Characteristics of wrong-way driving behaviors were analyzed and statistical analyses were conducted to identify the contributing factors of wrong-way crashes on freeway. The state-of-the-art roadway safety management process recommended by the Highway Safety Manual (HSM) was adopted to diagnose the wrong-way driving behavior on Illinois freeway and develop the specific wrong-way crashes management procedures. The first three steps, network screening, diagnosis and countermeasure selection was developed in details. The whole procedure developed could be used to guide the management of freeway wrong-way crashes in the future. The specific procedure of transportation network review, candidate location identification and site ranking for freeway wrong-way crashes was established firstly. Based on the collected wrong-way crash data, the safety performance function (SPF) for wrong-way crashes on freeway was developed with the annual average daily traffic (AADT) and segment length being the independent variables. The procedures for candidate wrong-way crash sites diagnoses with crash data, historic site data, field condition and other information were described step by step. The methods for contributing factors identification were proposed and the Haddon matrix for wrong-way crashes on freeway was constructed finally. Methods for selecting wrong-way crash countermeasures from the perspective of "four E's" based on crash analysis finding, site-specific contributing factors and geographical characteristics were discussed, and research needs on wrong-way crash management in the future were recommended finally.

This research presents theoretically an automated vehicle merging control which is an important subsystem of AHS. The goal of the system is to automatically control the vehicle merging from ramp to the AHS lane in an efficient, smooth and safe manner. The entire merging process is divided the a speed adjustment stage and a lane merging stage. Three important parameters; acceptability, availability and pursuability are analyzed to characterize the AHS lane gap features. Three control guidance laws (linear, optimal and parabolic speed profile) are developed to describe the desired behaviors of the merging vehicle based on the merging quality and safety consideration. The desired states of the merging vehicle are generated through the outer loop by specified control guidance law. The tracking errors compared with desired states are eliminated by the proper design of controllers in the inner loop. Both longitudinal and lateral controller are designed using the sliding mode control theory which can handle the model nonlinearities and uncertainties of the vehicle dynamics. Two new sliding mode methods are proposed in the design of the lateral controller. The proposed system is evaluated and validated through computer simulations. The simulation results show that system performance is satisfactory under the various merging conditions for a smooth, efficient and safe merging. The system also supplies a basis for the further research on the multiple merging control system and the lane changing control system. / Ph. D.

Research conducted over the past three years in the Vehicle Analysis and Simulation Laboratory at Virginia Tech has resulted in the development and validation of algorithms for the detection of driver drowsiness. Specifically, the goal of the research has been to develop the best possible drowsiness-detection algorithms using measures that can be computed while a vehicle is in motion with minimal interference with the driver. The results of these studies, which have been previously reported, generally support the feasibility of drowsy-driver detection and indicate that further analysis and refinement of the algorithms is warranted. This thesis researches several methods of refining existing driver-status algorithms, the integration of driver-performance deterioration measures, and the selection of appropriate alarm thresholds to be used in test and evaluation study. The results of five algorithm optimization refinements are described. Chapter 2 reports that the elimination of outlier dependent measure data prior to algorithm development was found not to improve algorithm accuracy. Chapter 3 describes that the addition of cross product and squared terms to the algorithms did not provide consistent improvement in algorithm accuracy. Chapter 4 reports that, although time-on-task variables were found to have some improved capability, they did not consistently add to the accuracy of the algorithms. / Master of Science

Roundabout installations are becoming common practice among DOTs and other local governments due to their superior safety attributes compared to other conventional at-grade intersections, especially stop-control and uncontrolled intersections. Current U.S. national guidelines for roundabout illumination recommend systematic illumination for all roundabouts. This recommendation might become a potential hindrance to desired widespread installations due to implied financial costs, especially in rural areas because the competing stop-control and uncontrolled intersections can be kept unlit. Interestingly rural roundabouts in most countries around the world are not illuminated as indicated by a recent survey of international roundabout illumination policies and standards from 45 countries. Also, review of intersection safety literature does not identify any publication that supports a systematic illumination policy of U.S. roundabouts. In fact, despite this recommendation there is no quantitative research on influence of illumination levels on nighttime safety at roundabouts and little on conventional intersections. Conversely, the literature shows a significant number of published studies which have indicated that currently recommended illumination levels on roadways can be reduced without compromising nighttime safety. This dissertation evaluates the link between roundabout crashes and different illumination levels. At the beginning of this dissertation research, there was no available repository of quantitative intersection illumination levels which could be used in highway safety research. Also, existing protocols for measurement require expensive light meters and are extremely time consuming to follow, making them impractical to use to study a large number of intersections. Consequently, this dissertation first evaluates the relationship with the best available data. The best available intersection illumination data was obtained from the Minnesota data contained in the Highway Safety Information System (HSIS). Minnesota crash and illumination data from 2003 to 2010 were analyzed. This illumination data was a qualitative description of intersection illuminating schemes and/or luminaire arrangement. Therefore, this dissertation also developed a cost-effective, accurate, and rapid method for measurement of quantitative intersection illumination data, and applied the developed protocol to a case study in Georgia. The measured intersection illumination was analyzed together with crash data obtained from GDOT for 2009 to 2014. The results of a naive analysis on the best available data indicated among other findings that the presence of lighting can provide approximately 61 percent lower total nighttime crash rate compared to the unlit condition. Also, providing illumination to the roundabout circle alone can yield about 80 percent of the benefits (55 percent reduction from unlit condition) of illuminating both the roundabout circle and approaches (66 percent reduction from unlit condition). Field test results for the camera calibration indicate that the average intersection illuminance derived from the protocol is within 4 percent difference of the actual average intersection illumination estimated from following the existing protocols. Next, despite limited roundabout data and potential issues of selection bias which could not be addressed in this dissertation, a cautious roundabout illumination specific crash modification factor was estimated with a negative binomial regression model. The model results showed that an increase of 1 lux in average roundabout illuminance will result in a 4.72 percent reduction in expected number nighttime crashes. The results of this work are useful in creating a sound framework for DOTs and other transportation agencies to determine the most appropriate level of illumination for roundabouts. This study also makes a number of significant contributions to highway safety research. First, this work is the first quantitative study on the impact of illumination on safety at roundabouts. The status-quo for highway safety research regarding the impacts of illumination had been to treat road lighting as a binary (Lit/Unlit) variable. However, even in most places without purposely-built road lighting there is usually ambient lighting from abutting facilities such as a gas stations or a store. Second, this dissertation is the first documented application of the photographic method to roundabouts. It is also the first documented application of the photographic method’s camera specific constant calibration approach to transportation field measurements. Previous documented application of the photographic method to transportation field measurements used an exposure specific calibration approach. Unlike the camera specific constant calibration approach, the exposure specific approach is rigid and field measurements must always be done at the exposure settings used in calibrating the camera. Thirdly, this work demonstrates the first developed procedure to developing uniformity (contour) plots from the photographic method. Next, this work can serve as the basis for initial efforts to create an illumination specific quantitative crash modification factor. Currently, the Highway Safety Manual is lacking in this important safety parameter. Last, but not the least this work offers procedures for collecting luminance data from the field and also documents a database of intersection illumination levels and intersection characteristics which can be used by future research.

Master of Science / Department of Civil Engineering / Sunanda Dissanayake / Kansas experienced about 60,000 crashes annually from 2013 to 2016, 25% of which occurred at urban intersections. Hence, urban intersections in Kansas are one of the most critical locations in terms of frequency of crashes. Therefore, an accurate prediction of crashes at these locations would help identify critical intersections with a higher probability of an occurrence of crash, which would help in selecting appropriate countermeasures to reduce those crashes. The crash prediction models provided in the Highway Safety Manual (HSM) predict crashes using traffic and geometric data for various roadway facilities, which are incorporated through Safety Performance Functions (SPFs) and Crash Modification Factors. The primary objective of this study was to estimate calibration factors for different types of urban intersection in Kansas. This study followed the crash prediction method and calibration procedure provided in the HSM to estimate calibration factors for four different urban intersection types in Kansas: 3-leg unsignalized intersections with stop control on the minor approach (3ST), 3-leg signalized intersections (3SG), 4-leg unsignalized intersections with stop control on the minor approach (4ST), and 4-leg signalized intersections (4SG). Following the HSM methodology, the required data elements were collected from various sources. The Annual Average Daily Traffic (AADT) data were extracted from Kansas Crash Analysis & Reporting System (KCARS) database and GIS Shapefiles downloaded from Federal Highway Administration website. For some of 3ST and 3SG intersections, minor-street AADT was not available. Hence, multiple linear regression models were developed for the estimation of minor-street AADT. Crash data were extracted from the Kansas Crash Analysis and Reporting System database, and other geometric data were extracted using Google Earth. The HSM requirement for sample size is 30 to 50 sites, with at least 100 crashes per year for the study period for the combined set of sites. In this study, the study period for 3ST, 3SG, and 4SG intersections were taken as 2013 to 2015, and 2014 to 2016 for 4ST, based on the availability of recent crash data at the beginning of the calibration procedure for each facility type. The sample size considered for calibration was 234 for 3ST, 89 for 3SG, 167 for 4ST, and 198 for 4SG intersections. Out of the 234 3ST intersections, minor-street AADT was estimated using multiple linear regression models for 106 intersections. For 3SG intersections, minor-street AADT was estimated for 21 out of the 89 intersections. The calibration factors for these facility types were estimated to be 0.64 for 3SG, 0.51 for 3ST, 1.17 for 4SG, and 0.61 for 4ST when considering crashes of all severities. Considering only the fatal and injury crashes, the calibration factors were estimated as 0.52 for 3SG, 0.40 for 3ST, 2.00 for 4SG, and 0.73 for 4ST. The calibration factors show that the HSM methodology underpredicted crashes for 4SG, and overpredicted crashes for other three intersection types. The reliability of the calibration factors was assessed with the help of Cumulative Residual plots and coefficient of variation. The results from the goodness-of-fit tests showed that the calibration factors were not reliable and showed bias in the prediction of crashes. Hence, calibration functions were developed, and their reliability were examined. The results showed that calibration functions had better reliability as compared to calibration factors, with more accuracy in crash prediction. The findings from this study can be used to identify intersections with a higher probability of having crashes in the future. Suitable countermeasures can be applied at critical locations which would help reduce the number of crashes at urban intersections in Kansas; thus increasing the safety.

Travelers experience different transportation-related problems on roadways ranging from congestion, delay, and crashes, which are partially due to growing background traffic and traffic generated by new developments. With regards to congestion, metropolitan planning organizations (MPOs) pursue a variety of plans for mitigating congestion. These plans include, amongst other measures, imposing impact fees. The current research evaluates how delay and safety can be incorporated in the mitigation process as special impact fees. This study also evaluates traffic projection methodologies used in traffic impact studies. Traffic volume is a critical factor in determining both current and future desired and undesired highway operations. Highway crashes are also influenced by traffic volume, as a higher frequency of crashes is expected at more congested locations and vice versa. Accurately forecasted traffic data is required for accurate future planning, traffic operations, safety evaluation, and countermeasures. Adhering to the importance of accurate traffic projection, this study introduces a simplistic traffic projection methodology for small-scale projection utilizing three parameters logistic function as a forecasting tool. Three parameters logistic function produced more accurate future traffic prediction compared to other functions. When validation studies were performed, the coefficient of correlation was found to be above 90 percent in each location. The t-values for the three parameters were highly significant in the projection. The confidence intervals have been calculated at a 95 percent confidence level using the delta method to address the uncertainty and reliability factor in the projection using logistic function. A delay mitigation fee resulting from increases in travel time is also analyzed in this research. In regular traffic flow, posted speed limit is the base of measuring travel time within the segment of the road. The economic concept of congestion pricing is used to evaluate the impact of this travel time delay per unit trip. If the relationship between the increase in time and trip is known, then the developer can be charged for the costs of time delays for travelers by using that relationship. The congestion pricing approach determines the average and marginal effect of the travel time. With the known values of time, vehicle occupancy, and number of travel days per year, the extra cost per trip caused by additional trips is estimated. This cost becomes part of the mitigation fee that the developer incurs as a result of travel time delays for the travelers due to the development project. Using the Bureau of Public Road (BPR) travel time function and parameters found in 2000 HCM (Highway Capacity Manual), the average and marginal travel times were determined. The value of time was taken as $7.50 per hour after reviewing different publications, which relate it to minimum wage. The vehicle occupancy is assumed as 1.2 persons per vehicle. Other assumptions include 261 working days per year and 4 percent rate of return. The total delay impact fee will depend on the number of years needed for the development to have effect. Since the developer is charged a road impact fee due to constructions cost for the road improvement, the delay mitigation fee should be credited to the road impact fee to avoid double charging the developer. As an approach to incorporate safety into mitigation fees, the study developed a crash prediction model in which all factors significantly influencing crash occurrences are considered and modeled. Negative binomial (NB) is selected as the best crash modeling distribution among other generalized linear models. The developed safety component of the mitigation fee equation considers scenarios in which the proposed new development is expected to increase crash frequency. The mitigation fee equation is designed to incorporate some roadway features and traffic characteristics generated by the new development that influence crash occurrence. Crash reduction factors are introduced and incorporated in the safety mitigation fees equation. The difference between crash frequency before and after the development is multiplied by the crash cost then divided by the trips to obtain crash cost per trip. Crash cost is taken as $28,000/crash based on literature review. To avoid double charging the developer, either the road impact fee is applied as a credit to the delay mitigation fee or vice versa. In summary, this study achieved and contributed the following to researchers and practitioners: ... Developed logistic function as a simplified approach for traffic projection ... Developed crash model for crash prediction ... Developed safety mitigation fee equation utilizing the crash modeling ... Developed delay mitigation fee equation using congestion pricing approach

Doctor of Philosophy / Civil Engineering / Sunanda Dissanayake / Rural roads account for 90.3% of the 140,476 total centerline miles of roadways in Kansas. In recent years, rural fatal crashes have accounted for about 66% of all fatal crashes. The Highway Safety Manual (HSM) provides models and methodologies for analyzing the safety of various types of highways. Predictive methods in the HSM were developed based on national trends and data from few states throughout the United States. However, these methodologies are of limited use if they are not calibrated for individual jurisdictions or local conditions. The objective of this study was to analyze the HSM calibration procedures for rural multilane segments and intersections in Kansas. The HSM categorizes rural multilane segments as four-lane divided (4D) and four-lane undivided (4U) segments and rural multilane intersections as three-legged intersections with minor-road stop control (3ST), four-legged intersections with minor-road stop control (4ST), and four-leg signalized intersections (4SG). The number of predicted crashes at each segment was obtained according to the HSM calibration process. Results from calibration of rural segments indicated that the HSM overpredicts fatal and injury crashes by 50% and 65% and underpredicts total crashes by 48% and 64% on rural 4D and 4U segments, respectively. The HSM-given safety performance function (SPF) regression coefficients were then modified to capture variation in crash prediction. The adjusted models for 4D and 4U multilane segments indicated significant improvement in crash prediction for rural Kansas. Furthermore, Kansas-specific safety performance functions (SPF)s were developed following the HSM recommendations. In order to develop Kansas-specific SPF, Negative Binomial regression was applied to obtain the most suitable model. Several additional variables were considered and tested in the new SPFs, followed by model validation on various sets of locations. The Kansas-specific SPFs are capable of more accurately predicting total and fatal and injury crashes on multilane segments compared to the HSM and the modified HSM models. In addition to multilane segments, rural intersections on multilane highways were also calibrated according to the HSM methodology. Using crash modification factors for corresponding variables, SPFs were adjusted to obtain final predicted crash frequency at intersections. Obtained calibration factors indicated that the HSM is capable of predicting crashes at intersections at satisfactory level. Findings of this study can be used for improving safety of rural multilane highways.

The author of the Highway Safety Manual (HSM) Part B developed a predictive method for safety management. A software tool for highway safety system analysis called the SafetyAnalyst is developed basing on HSM Part B. The author describes an effort to evaluate the feasibility of SafetyAnalyst in Oregon. Seven sample highway sections in Oregon are selected to demonstrate the SafetyAnalyst network screening application. The purpose of this research is to assess if the SafetyAnalyst is compatible with current Oregon Department of Transportation (ODOT) databases such as the Highway Inventory Detail Report, Lane Report, etc. The author also presents an effort to identify current data deficiencies and identify a feasible solution for addressing these deficiencies. SafetyAnalyst requires hundreds of input variables. Not all of these variables are included in the current Oregon database. Those input variables that require additional data collection are described as well. This thesis also includes a sensitivity test for input variables to prioritize required variables. Finally, the author determines that the SafetyAnalyst can be used in Oregon. This research also provides a variable priority for the SafetyAnalyst users. / Graduation date: 2012