Disagreements regarding to what degree right-turn lanes improve or worsen the safety of intersections and driveways provided the motivation and the need for this study. The objectives of this study were to: a) carry out an in-depth study to determine the safety impacts of right-turn movements in different contexts, and b) develop safety-based volume warrants for right-turn lanes if safety indeed improves. Lack of adequate study on the applicability of past warrants and guidelines for the specific context of right-turn movements made from major uncontrolled approaches at unsignalized intersections, and particularly driveways, on two-lane roadways provided the scope for this study. Five-year historical data of statewide traffic crashes reported on Minnesota's twolane trunk highways were analyzed using binary/multinomial logistic regressions. Conflicts due to right turns were analyzed by fitting least squares conflict prediction models based on the data obtained from field surveys and traffic simulations. The safety impacts of rightturn lanes were determined through crash-conflict relationships, crash injury severity, and crash and construction costs. The study found that the probabilities of right-turn movement related crash ranged from 1.6 to 17.2% at intersections and from 7.8 to 38.7% at driveways. Rear-end, samedirection- sideswipe, right-angle and right-turn crash types constituted 96% of right-turn movement related crashes. Rear-end crash probabilities varied from 13.7 to 46.4% at approaches with right-turn lanes and from 37.9 to 76.9% otherwise. The ratios of rearend/ same-direction-sideswipe crashes to conflicts were 0.759 x 10-6 at approaches with right-turn lanes and 1.547 x 10-6 otherwise. iv Overall, right-turn lanes reduced right-turn movement related crash occurrences and conflicts by 85% and 80%, respectively. Right-turn lanes also reduced crash injury severity, hence, reducing the economic cost by 26%. Safety benefits, in dollars, realized with the use of right-turn lanes at driveways were 29% and 7% higher compared to those at intersections at low and high speed conditions respectively for similar traffic conditions. Depending on roadway conditions, interest rate and construction costs, the safety-based volume thresholds ranged from 3 to 200 right turns per hour during the design hour at intersection approaches, and from 2 to 175 right turns at driveway approaches. / Civil and Environmental Engineering / College of Engineering

The huge financial and societal cost associated with traffic crashes and the fact that more than half of them occur at junctions, revealed the need for further research in the field of junction safety. This research aims to investigate the quantitative impact of junctions in relation to other selected parameters, on the frequency of road crashes in urban areas in the State of Florida. Mathematical models were developed with the use of loglinear analysis method for different traffic volumes in and out of junction. In addition, sensitivity analysis was performed in order to better understand the impact of selected parameters to the total number of crashes. The analysis has led to several conclusions such as that angle and left turn collisions have much higher probability of occurrence at junctions and that crashes which occur at junctions are much more probable for low and medium volumes compared to no-junctions. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

There is increased interest in building modern roundabouts in Georgia and in the United States because of the safety and operational benefits that can be realized from this type of intersection. With this interest comes the increasing need to be able to estimate the capacity that a roundabout can provide after it is built. In the early 2000s, a National Cooperative Highway Research Program (NCHRP) study was conducted that, among other tasks, developed single-lane and multi-lane roundabout capacity estimation equations. These equations, presented in the Highway Capacity Manual 2010 (HCM 2010), can be calibrated using locally determined values of follow-up headway and critical headway. This study was designed to calibrate the HCM 2010 roundabout capacity equation for single-lane roundabouts to driving conditions in Georgia. In order to develop estimates of the calibration parameters, video imagery was recorded for 13 approaches at six roundabouts in Georgia for approximately two hours during the peak period. A total of 29.5 hours of video was recorded. Data from three of these roundabouts forms the basis of this thesis. The videos were processed by a Java program to collect time stamps that were subsequently used in Microsoft Excel to calculate the follow-up and critical headway values required for calibration. The values of critical headway and follow-up headway that were found from the video data are presented in the results as well as the single-lane capacity equations calibrated from the data. Two types of analysis were done, one that includes exiting vehicles and one that does not include exiting vehicles. When exiting vehicles were excluded, the weighted average of follow-up and critical headway were found to be 3.46 and 4.17 seconds respectively and when exiting vehicles were included in the analysis the weighted averages of the follow-up and critical headway were found to be 2.80 seconds and 3.34 seconds respectively. It was found that exiting vehicles do have an impact on the operations at the roundabout in most cases, and including exiting vehicles in the analysis tends to increase the capacity predicted by the calibrated equations.

Intersection crashes accounted for 47 percent of the total number of crashes in the State of Georgia from 2000-2005, and as a location where crashes occur, represent the largest number of crash locations in the state. Federal legislation requires states to implement statewide safety plans to reduce fatalities, crashes, and improve safety. Intersections vary in different ways and there are individual factors that can cause an intersection to be safer or more dangerous than another. Acquiring better, uniform, and more updated information with regard to intersection crashes will enable transportation officials to prescribe policies for improving safety in an easier and more expedited manner. This thesis recommends a five-part program for intersection safety that will enable Georgia transportation officials to better analyze, identify, and implement countermeasures at intersections that are determined to be the most hazardous. The plan consists of: 1. Standardized Hazardous Intersection Identification Method 2. Statewide Public Involvement task force 3. Automated Police Crash Reporting Through Improved Technologies 4. Strategic Highway Safety Plan (SHSP) Intersection Safety Strategies (8 State Comparison) 5. Statewide Minimal Intersection Safety Equipment The five parts of this plan lead to a statewide standard method of analyzing intersections based on uniform collection methods and uniform equipment statewide.

Thesis (M. Tech.) - Central University of Technology, Free State, 2007

In the last decades, population growth has been outpacing transportation infrastructure growth, and today's transportation professionals are challenged to meet the mobility needs of an increasing population. The effectiveness of the transportation system is an essential constituent of people's daily lives as they commute between different points of interest. Studies show that at many highway junctions, congestion continues to worsen, and drivers are experiencing greater delays and higher risk exposures. Engineers have very little resources to handle this increase in population. One solution to resolve and alleviate congestion due to increasing traffic volumes and travel demands relies in implementing alternative designs. This approach will help traffic engineers determine which design will be the most appropriate for a particular location. This study compares and evaluates the Diverging Diamond Interchange (DDI), which is an unconventional design, to Partial Cloverleaf (ParClo) types A4 and B4 interchange designs by evaluating different Measure of Effectiveness (MOEs). Using microsimulation platform AIMSUN, each interchange type was evaluated for low, medium and high traffic flows. The analysis revealed that the DDI with four through lanes performed better than the ParClo A4 for unbalanced conditions, the DDI with six though lanes had similar results as the ParClo B4 for very high volumes. In terms of queue, the DDI design had a much better performance. The results from the analysis help in providing guidelines to the decision makers for selecting the best alternative in terms of performance. / by Borja Galletebeitia. / Thesis (M.S.C.S.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.

As the modern roundabout continues to grow in popularity within the United States, more states are considering or implementing statewide roundabout programs and policies. To assist states with the implementation of statewide roundabout programs and policies, an analytical review of statewide roundabout programs and policies was conducted through an examination of literature, interviews, and data pertaining to the construction of roundabouts. The roundabout policy type for each state and the District of Columbia was located, and assigned to a roundabout policy type based on the strength of the identified policy type. In addition, a series of per capita analyses of the statewide roundabout policies was performed, as was a qualitative SWOT (Strengths, Weaknesses, Opportunities and Threats) analysis. The results of the analysis show that the strength of a statewide roundabout policy is correlated to the number of roundabouts in a state, and states should consider implementing or strengthening their policies if they seek to expand the use of roundabouts in their jurisdiction. In addition, the perception of roundabouts, both by the general public and internal to the state DOTs, also continues to hinder the further implementation of roundabouts, and education should be utilized to minimize these obstacles. Furthermore, states should utilize identified successful implementation procedures, and should be cognizant of reasons for implementation failure, as they pursue the further use of roundabouts by their agency.

The accident rate at an intersection is one attribute used to evaluate the hazard associated with the intersection. Two techniques traditionally used to make such evaluations are the rate-quality technique and a technique based on the confidence interval of classical statistics. Both of these techniques label intersections as hazardous if their accident rate is greater than some critical accident rate determined by the technique. An alternative technique is one based on a Bayesian analysis of available accident number and traffic volume data. In contrast to the two classic techniques, the Bayesian technique identifies an intersection as hazardous based on a probabilistic assessment of accident rates. The goal of this thesis is to test and compare the ability of the three techniques to accurately identify traffic intersections known to be hazardous. Test data is generated from an empirical distribution of accident rates. The techniques are then applied to the generated data and compared based on the simulation results.

M.Ing. (Mechanical Engineering) / The purpose of this study was to investigate the accuracy of SOAP84-simulations of delay and percentage stops at isolated signalized intersections. In the application, capacity was distinguished in terms of lane configuration only. Results at the intersections showed SOAP overestimating both delay and percentage stops by as much as 100%. It is recommended that the same investigations be repeated with more accurate information on the capacity of the intersections.

Traditional intersections have always caused congestion, delay, and accidents. There are numerous geometric intersection designs that best fit each situation. This study performed an operational and safety comparison with unsignalized/signalized offset, Tintersections, a two-lane roundabout, and a modified roundabout to decrease the overall travel delay and increase the safety using a case study. Using data from a government source, all designs were tested in a calibrated micro simulation model and traffic signals were optimized using a signal optimization platform. Each design was tested with various balancing schemes, left turn percentages, and hourly volumes to determine the failure point. The unsignalized/signalized offset T-intersections, two-lane roundabout, and modified roundabout were compared by throughputs, travel delay, and travel time. After analysis, it was determined that the modified roundabout performed the best out of any design. All approaches had minimum travel delay while reducing the number of conflict points considerably with the modified roundabout. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection