Organizational Unit:
School of Civil and Environmental Engineering
School of Civil and Environmental Engineering
Permanent Link
Research Organization Registry ID
Description
Previous Names
Parent Organization
Parent Organization
Organizational Unit
Includes Organization(s)
Organizational Unit
Organizational Unit
Organizational Unit
ArchiveSpace Name Record
Publication Search Results
Now showing
1 - 10 of 35
-
ItemESTIMATING THE EFFECT OF VEHICLE SPEEDS ON BICYCLE AND PEDESTRIAN SAFETY ON THE GEORGIA ARTERIAL ROADWAY NETWORK(Georgia Institute of Technology, 2020-07-09) Arias, Daniel F.Despite a decreasing trend in overall crashes, bicyclist and pedestrian fatalities have increased steadily since 2009 in the United States (Cicchino & Hu 2016). A large body of research suggests vehicle speeds are a key contributing factor for crashes (Elvik et al. 2019). Furthermore, vehicle impact speed has been identified as the principal determinant of severity and death in the event of a pedestrian crash (Tefft 2013). However, there have been few studies of bicycle or pedestrian crash probability that incorporate detailed vehicle speed data. Newly available probe vehicle data in the state of Georgia makes it possible to study the relationship between bicycle and pedestrian crashes and speed across the network of Georgia arterial roadways. The analysis uses INRIX® speed data and the Georgia DOT crash database and relates these data in a Negative Binomial crash count model for the year 2017. Models using speed percentiles (85th, 50th and 15th) and models using speed differences (85th - 50th and 50th - 15th percentile) are compared. A small set of covariates are included. This study shows that the high speed difference (85th - 50th percentile) is a robust indicator of bicycle and pedestrian crash frequency on Georgia arterial roadways. The high speed difference outperformed the low speed difference (50th - 15th percentile), suggesting that the high end of the distribution is more important to crash prediction than the low end. Additionally, speed percentile models showed no clear, intuitive relationship to bicycle and pedestrian crashes. In light of these results, planners and policymakers should identify arterial roadways with high speeds, high spread of speeds at the top end of the distribution, and high bicyclists and pedestrian activity. To do so, a complete bicycle and pedestrian count data collection effort is needed. These target roadways should be considered for treatments which prioritize the reduction of the fastest speeds and limitation of exposure for unprotected road users. Finally, the practice of setting the speed limit at the 85th percentile speed (NTSB 2017) should end. Road user safety must supplant vehicle throughput and access to create a sustainable, equitable and just transportation system in Georgia.
-
ItemSafety analysis of centerline rumble strips along rural two-lane undivided highways in Georgia(Georgia Institute of Technology, 2017-12-14) Pena, Marisha S.Vehicle crashes involving crossing over the roadway centerlines are among the most severe types of collisions nationwide. To address this issue, the Georgia Department of Transportation (GDOT) started implementing centerline rumble strips (CLRS) in rural locations across Georgia in 2005 and 2006. CLRS produce both an audible and tactile warning to alert drivers of impending lane departure into the lane of oncoming traffic. As of 2015, approximately 200 miles of CLRS have been installed by GDOT as a countermeasure for crossover crashes along rural two-lane undivided highways. This study evaluates the safety impacts of CLRS deployments in Georgia by analyzing two years of before and two years of after periods to evaluate the safety impacts associated with nine treatment sites and a control group of comparison sites with similar traffic and physical characteristics. The study dataset consisted of 154 target crashes along 126.46 miles of CLRS treatment sites and 1,391 crashes along control group sites. The empirical Bayes method was used to develop a crash modification factor for CLRS of 0.66, indicating a 34% reduction in crashes involving centerline crossings associated with the installation of centerline rumble strips. The sample size of fatal and injury crashes was too small to obtain separate crash modification factors for fatal crashes and injury crashes. The favorable crash modification factor (0.66) found in this study supports wider use of centerline rumble strips as a safety measure to address crashes involving vehicles that cross the centerline of the roadway. In addition to the safety analysis, this study also provided insights into the crash reporting process by conducting a comprehensive manual review of more than 17,000 crash reports. Approximately 6% of target crashes were found to be misclassified due to coding errors.
-
ItemAnalysis of trucking variability in roadway network energy using basic safety message data(Georgia Institute of Technology, 2017-12-11) Bolen, JohnThis experiment uses VISSIM to replicate the message broadcasted by connected vehicles and plugs it into an energy calculator in order to determine how the energy usage of a vehicle fleet changes as the truck percentage of the fleet changes. By replicating the connected vehicle message, it also allows researchers to determine the extent to which connected vehicle data can be used in future experiments. This experiment began with the building of a microscopic simulation traffic model the North Avenue Corridor in Atlanta, GA, modeling the signal timing, traffic volumes, and overall characteristics of all 19 signalized intersections within the three mile corridor. With this done, the model was run ten different times for each of seven different fleet compositions, each with a different percentage of single unit delivery trucks and tractor trailers. The data files directly outputted into VISSIM were then processed in such a way that they mimicked the standardized message broadcasted by connected vehicles. After this, the processed files were run through the energy calculator in order to determine the energy for each vehicle type as well as for the entire fleet. From this experiment, it was determined that adding more trucks to a vehicle fleet has a small but definite change in the per-vehicle energy for passenger cars. The per-vehicle change for trucks was larger than that of cars, but due to extreme variability in the truck results, the extent to which increasing truck percentage affects trucks is inconclusive. Future research into this topic should include much larger sample sizes than ten runs per fleet composition, and should include more fleet compositions in the range of 10% trucks to 50% trucks. Future research may also include sampling the connected vehicle replica data to determine the expected sample error from various connected vehicle market penetration rates.
-
ItemSensitivity analysis of operational performance under conventional diamond interchange and diverging diamond interchange(Georgia Institute of Technology, 2017-12-11) Park, Sung JunRapidly growing traffic volumes and changes in traffic patterns over time have forced many intersections and interchanges into sub-optimal operation. Diverging diamond interchange (DDI) is one of many innovative interchange designs currently being proposed and implemented to better accommodate these changes. This study compares the operational performance of a conventional diamond interchange (CDI) and a DDI at different traffic volumes and turning movement combinations, and explores conditions for which one interchange design may be more advantageous over the other. To achieve this objective, traffic simulation models built using the microscopic simulation software, VISSIM, and procedures involving the Critical Lane Volume (CLV) method were used to conduct sensitivity analyses at different traffic conditions and to explore differences in delay, travel time, queue length, number of stops, and volume-to-capacity ratio between the two interchange designs studied. The results of the study show that the DDI will have better operational performance at high cross street traffic volumes with high left-turn ratio (above 50%), while the CDI will perform better at low cross street traffic volumes with low left-turn ratio (below 30%). The through/left proportion where the CDI and DDI has similar performance is dependent to the cross street cross sections. This study is one of the first to examine in detail the parameters and conditions that are best accommodated by the DDI related to conventional interchanges. Findings from this study can support planning and decision making processes associated with the implementation of DDIs.
-
ItemDeveloping freeway merging calibration techniques for analysis of ramp metering In Georgia through VISSIM simulation(Georgia Institute of Technology, 2016-05-03) Whaley, Michael T.Freeway merging VISSIM calibration techniques were developed for the analysis of ramp metering in Georgia. An analysis of VISSIM’s advanced merging and cooperative lane change settings was undertaken to determine their effects on merging behavior. Another analysis was performed to determine the effects of the safety reduction factor and the maximum deceleration for cooperative braking parameter on the simulated merging behavior. Results indicated that having both the advanced merging and cooperative lane change setting active produced the best results and that the safety reduction factor had more influence on the merging behavior than the maximum deceleration for cooperative braking parameter. Results also indicated that the on-ramp experienced unrealistic congestion when on-ramp traffic was unable to immediately find an acceptable gap when entering the acceleration lane. These vehicles would form a queue at the end of the acceleration lane and then be unable to merge into the freeway lane due to the speed differential between the freeway and the queued ramp traffic. An Incremental Desired Speed algorithm was developed to maintain an acceptable speed differential between the merging traffic and the freeway traffic. The Incremental Desired Speed algorithm resulted in a smoother merging behavior. Lastly, a ramp meter was introduced and an increase in both the freeway throughput and overall speeds was found. Implications of these findings on the future research is discussed.
-
ItemA methodology for separation of multiple distributions in arterial travel time data(Georgia Institute of Technology, 2015-05-15) Anderson, James MillerMultiple distribution travel time data has been observed in signalized corridors as well as freeway corridors. This behavior is typically caused by congestion, uncoordinated signals, or routes through a coordinated corridor that are not a priority. On the SR140 corridor near the Jimmy Carter Boulevard / I-85 Interchange, it was found that the travel times recorded on the corridor contained multiple distributions and thus a methodology was sought to properly separate the distributions in order to perform more robust statistical analysis. Next, an R statistical language library was found, called “mixtools”, which contained a multiple gamma distribution fitting function called “gammamixEM”. Gamma distributions were chosen for this application as typical travel time distributions tend contain a one sided tail. This function was used in conjunction with a monte-carlo approach to find fits for one to six distributions. The accuracy of the fit was confirmed through visual inspection of the plotted distributions. Then, the Akaike Information Criteria were used to compare the fits to determine the best fit number of distributions. This thesis contains a detailed outline of the algorithm as well as results from the algorithm for the combined Tuesday dataset from this project. It was found that the approach worked well for 60 out of 70 cases. In the 10 cases that were not ideal, the distributional fits make sense on a statistical level, however, for the purposes of the before and after project the next best Akaike Information Criteria value fit may need to used. These 10 cases tended to split obvious single distributions into two distributions, which is not desirable in a before and after analysis where one is not only testing individual distributions before and after construction but also determining if distributions were created or removed as a result of the change in operation of the interchange.
-
ItemComprehensive on-street bicycle facilities: an approach for incorporating traffic signal operational strategies for bicycles(Georgia Institute of Technology, 2015-05-15) Curtis, Eddie J.Less than 1% of work and school trips are completed by bicycle in the United States. Comprehensive bicycle facilities improve bicycle ridership by including a diverse set of strategies that accommodate the bicycle mode and seek to minimize the Level of Traffic Stress experienced by riders. Traffic Signal Operational Strategies for Bicycles (TSOSB) are an integral component of comprehensive bicycle facilities. This research presents a methodology to identify critical zones for implementation of TSOSB. After identifying critical zones a process for assessment of gaps in bicycle safety and comfort and convenience for signalized intersections within the critical zones is conducted. The outcome of the methodology is a prioritized list of signalized intersection that could benefit from the application of Traffic Signal Operational Strategies for Bicycles
-
ItemReal-time road traffic information detection through social media(Georgia Institute of Technology, 2015-05-15) Khatri, Chandra P.In current study, a mechanism to extract traffic related information such as congestion and incidents from textual data from the internet is proposed. The current source of data is Twitter, however, the same mechanism can be extended to any kind of text available on the internet. As the data being considered is extremely large in size automated models are developed to stream, download, and mine the data in real-time. Furthermore, if any tweet has traffic related information then the models should be able to infer and extract this data. To pursue this task, Artificial Intelligence, Machine Learning, and Natural Language Processing techniques are used. These models are designed in such a way that they are able to detect the traffic congestion and traffic incidents from the Twitter stream at any location. Currently, the data is collected only for United States. The data is collected for 85 days (50 complete and 35 partial) randomly sampled over the span of five months (September, 2014 to February, 2015) and a total of 120,000 geo-tagged traffic related tweets are extracted, while six million geo-tagged non-traffic related tweets are retrieved. The classification models for detection of traffic congestion and incidents are trained on this dataset. Furthermore, this data is also used for various kinds of spatial and temporal analysis. A mechanism to calculate level of traffic congestion, safety, and traffic perception for cities in U.S. is proposed. Traffic congestion and safety rankings for the various urban areas are obtained and then they are statistically validated with existing widely adopted rankings. Traffic perception depicts the attitude and perception of people towards the traffic. It is also seen that traffic related data when visualized spatially and temporally provides the same pattern as the actual traffic flows for various urban areas. When visualized at the city level, it is clearly visible that the flow of tweets is similar to flow of vehicles and that the traffic related tweets are representative of traffic within the cities. With all the findings in current study, it is shown that significant amount of traffic related information can be extracted from Twitter and other sources on internet. Furthermore, Twitter and these data sources are freely available and are not bound by spatial and temporal limitations. That is, wherever there is a user there is a potential for data.
-
ItemTraffic management alternatives for business improvement districts(Georgia Institute of Technology, 2014-05-19) Harris, Darren SamuelWhen a vehicle enters an intersection with insufficient space to exit on the opposite side the result is often the obstruction of pedestrians and other vehicles, this phenomenon is usually referred to as "blocking the box." The purpose of this study was to determine different characteristics of blocking that might be considered in determining the installment of a "Don't Block the Box" (DBTB) campaign. This study identified potentially problematic intersections in Atlanta, Georgia and collected information, such as the number of vehicles that block the intersection (box junction), the amount of green time with blocking, and the percentages in which approaches were blocked. Based on the results it was found the characteristics of the number of blockers, percentage of green time with blocking, and the percentage of lost capacity are excellent indicators for a possible DBTB campaign. Organizations interested in potentially starting a DBTB should consider these characteristics part of the determination of suitability of DBTB for an intersection. Within this study is was found that the intersections of Peachtree Road & Highland Drive, Peachtree Road & Stratford Road, Peachtree Road & Lenox Mall Entrance, and 10th Street & Williams Street showed to be potential candidates for a DBTB campaign in Atlanta, Georgia. During the study period these intersections had high percentages of lost capacity, high number of blocks, and high percentages of green time with blocking. In conjunction with the DBTB data analysis a "DBTB survey" was developed. The objective of this survey was to help gain a better understanding of the current trends in DBTB campaigns around the United States. The "DBTB Survey" received 75 responses from 415 organizations around the nation, a 18.1% response rate. Six (60%) of the ten participants that currently have a DBTB campaign found a sufficient level of improvement in traffic operations and 46 of the total respondents (60%) proclaimed that if DBTB campaigns were shown to be an economical alternative for traffic management they would consider starting one to help congestion and safety.
-
ItemSafety impact study of centerline rumble strips in Georgia(Georgia Institute of Technology, 2014-01-13) Sin, Jerome Ga NokWithin the last decade, centerline rumble strips have become increasingly prevalent as a safety countermeasure on undivided roadways throughout the United States. Within the state of Georgia, nearly 200 miles of centerline rumble strips have been installed in an effort to address the severity and frequency of crashes involving the centerline. With several thousands of miles of new installations throughout the nation in the last decade, much literature on this subject is still being amassed. This paper will compile and summarize existing literature in order to provide a thorough overview of the latest information from around the United States regarding the safety, usage, and impacts of centerline rumble strips. Furthermore, this paper seeks to comprehensively determine the safety impacts of centerline rumble strips on undivided, rural highway facilities in the state of Georgia. This portion of the study will prepare an updated inventory of centerline rumble strip installations in Georgia and perform a before-after study using three methods: a direct before-after analysis, a comparison before-after analysis, and a comparative analysis. These analyses will incorporate data from crash databases, police records, and traffic records to produce results unique to Georgia. Lastly, this paper will determine the current status of centerline rumble strips and the potential short- and long-term safety, physical, and unintended effects of centerline rumble strips both in the state of Georgia and throughout the United States through a survey sent to all fifty state transportation agencies. Through literature compilation, safety analyses, and findings on the effects of centerline rumble strips, this paper will aid in the future of centerline rumble strips within Georgia and the United States.