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ASSESSING CRASH OCCURRENCE ON URBAN FREEWAYS USING STATIC AND DYNAMIC FACTORS BY APPLYING A SYSTEM OF INTERRELATED EQUATIONS
Title
ASSESSING CRASH OCCURRENCE ON URBAN FREEWAYS USING STATIC AND DYNAMIC FACTORS BY APPLYING A SYSTEM OF INTERRELATED EQUATIONS.
Creator
Pemmanaboina, Rajashekar, Abdel-Aty, Mohamed, University of Central Florida
Abstract / Description
Traffic crashes have been identified as one of the main causes of death in the US, making road safety a high priority issue that needs urgent attention. Recognizing the fact that more and effective research has to be done in this area, this thesis aims mainly at developing different statistical models related to the road safety. The thesis includes three main sections: 1) overall crash frequency analysis using negative binomial models, 2) seemingly unrelated negative binomial (SUNB) models...
Show moreTraffic crashes have been identified as one of the main causes of death in the US, making road safety a high priority issue that needs urgent attention. Recognizing the fact that more and effective research has to be done in this area, this thesis aims mainly at developing different statistical models related to the road safety. The thesis includes three main sections: 1) overall crash frequency analysis using negative binomial models, 2) seemingly unrelated negative binomial (SUNB) models for different categories of crashes divided based on type of crash, or condition in which they occur, 3) safety models to determine the probability of crash occurrence, including a rainfall index that has been estimated using a logistic regression model. The study corridor is a 36.25 mile stretch of Interstate 4 in Central Florida. For the first two sections, crash cases from 1999 through 2002 were considered. Conventionally most of the crash frequency analysis model all crashes, instead of dividing them based on type of crash, peaking conditions, availability of light, severity, or pavement condition, etc. Also researchers traditionally used AADT to represent traffic volumes in their models. These two cases are examples of macroscopic crash frequency modeling. To investigate the microscopic models, and to identify the significant factors related to crash occurrence, a preliminary study (first analysis) explored the use of microscopic traffic volumes related to crash occurrence by comparing AADT/VMT with five to twenty minute volumes immediately preceding the crash. It was found that the volumes just before the time of crash occurrence proved to be a better predictor of crash frequency than AADT. The results also showed that road curvature, median type, number of lanes, pavement surface type and presence of on/off-ramps are among the significant factors that contribute to crash occurrence. In the second analysis various possible crash categories were prepared to exactly identify the factors related to them, using various roadway, geometric, and microscopic traffic variables. Five different categories are prepared based on a common platform, e.g. type of crash. They are: 1) Multiple and Single vehicle crashes, 2) Peak and Off-peak crashes, 3) Dry and Wet pavement crashes, 4) Daytime and Dark hour crashes, and 5) Property Damage Only (PDO) and Injury crashes. Each of the above mentioned models in each category are estimated separately. To account for the correlation between the disturbance terms arising from omitted variables between any two models in a category, seemingly unrelated negative binomial (SUNB) regression was used, and then the models in each category were estimated simultaneously. SUNB estimation proved to be advantageous for two categories: Category 1, and Category 4. Road curvature and presence of On-ramps/Off-ramps were found to be the important factors, which can be related to every crash category. AADT was also found to be significant in all the models except for the single vehicle crash model. Median type and pavement surface type were among the other important factors causing crashes. It can be stated that the group of factors found in the model considering all crashes is a superset of the factors that were found in individual crash categories. The third analysis dealt with the development of a logistic regression model to obtain the weather condition at a given time and location on I-4 in Central Florida so that this information can be used in traffic safety analyses, because of the lack of weather monitoring stations in the study area. To prove the worthiness of the weather information obtained form the analysis, the same weather information was used in a safety model developed by Abdel-Aty et al., 2004. It was also proved that the inclusion of weather information actually improved the safety model with better prediction accuracy.
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Date Issued
2005
Identifier
CFE0000587, ucf:46468
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000587
Investigating and Facilitating the Transferability of Safety Performance Functions
Title
Investigating and Facilitating the Transferability of Safety Performance Functions.
Creator
Farid, Ahmed Tarek Ahmed, Abdel-Aty, Mohamed, Lee, JaeYoung, Eluru, Naveen, University of Central Florida
Abstract / Description
Safety performance functions (SPFs) are essential analytical tools in the road safety field. The SPFs are statistical regression models used to predict crash counts by roadway facility type, crash type and severity. The national Highway Safety Manual (HSM) is a generic guidebook used for road safety evaluation and enhancement. In it, default SPFs, developed using negative binomial (NB) regression, are provided for multiple facility types and crash categories. Roadway agencies, whether public...
Show moreSafety performance functions (SPFs) are essential analytical tools in the road safety field. The SPFs are statistical regression models used to predict crash counts by roadway facility type, crash type and severity. The national Highway Safety Manual (HSM) is a generic guidebook used for road safety evaluation and enhancement. In it, default SPFs, developed using negative binomial (NB) regression, are provided for multiple facility types and crash categories. Roadway agencies, whether public or private, may opt to not invest their resources in data collection and processing to develop own localized SPFs. Instead, the agencies may adopt the HSM's. However, the HSM's SPFs may not necessarily be applicable to any conditions. Hence, this research is focused on SPF transferability, specifically for rural divided multilane highway segments. Use of Bayesian informative priors to aid in the transferability of NB SPFs, developed for Florida, to California's conditions and vice versa is investigated. It is demonstrated that informative priors facilitate SPF transferability. Furthermore, NB SPFs are developed for Florida, Ohio, Illinois, Minnesota, California, Washington and North Carolina. That is to evaluate the transferability of each state's SPFs to the other states' conditions. The results indicate that Ohio, Illinois, Minnesota and California have SPFs that are transferable to conditions of each of the four states. Also, two methods are proposed for calibrating transferred SPFs to the destinations' conditions and are shown to outperform the SPF calibration methods in the road safety literature. Finally, a variety of modeling frameworks are proposed for developing and transferring SPFs of the seven aforementioned states to each state's data. Not a single model exhibits the best fit when transferred in all cases. However, the Tobit model, NB model and a hybrid model that coalesces the results of both perform the best in a substantial number of the transferred SPFs.
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Date Issued
2018
Identifier
CFE0007000, ucf:52054
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007000
Explore Contributing Geometric Factors and Built-Environment on Bicycle Activity and Safety at Intersections
Title
Explore Contributing Geometric Factors and Built-Environment on Bicycle Activity and Safety at Intersections.
Creator
Castro, Scott, Abdel-Aty, Mohamed, Cai, Qing, Eluru, Naveen, University of Central Florida
Abstract / Description
This study attempts to explore all factors associated with bicycle motor-vehicle crashes at intersections in order to improve bicycle safety and bicycle activity. Factors such as exposure (bicycle and vehicle volumes), existing facilities (bike lanes, sidewalks, shared-use paths), geometric design (# of lanes, speed limit, medians, legs, roadway conditions), and land-use were collected and evaluated using Poisson, Zero-Inflated Poisson, and Negative Binomial models in SAS 9.4 software....
Show moreThis study attempts to explore all factors associated with bicycle motor-vehicle crashes at intersections in order to improve bicycle safety and bicycle activity. Factors such as exposure (bicycle and vehicle volumes), existing facilities (bike lanes, sidewalks, shared-use paths), geometric design (# of lanes, speed limit, medians, legs, roadway conditions), and land-use were collected and evaluated using Poisson, Zero-Inflated Poisson, and Negative Binomial models in SAS 9.4 software. Increasing the bicycle travel mode can have positive lasting effects on personal health, the environment, and improve traffic conditions. Deterrents that keep users from riding bicycles more are the lack of facilities and most importantly, safety concerns. Florida has consistently been a national leader in bicyclist deaths, which made this area a great candidate to study. Vehicle and bicycle volumes for 159 intersections in Orlando, Florida were collected and compared with crash data that was obtained. All existing facilities, geometric design properties, and land-uses for each intersection were collected for analysis. The results confirmed that an increase of motor-vehicles and bicyclists would increase the risk of a crash at an intersection. The presence of a keyhole lane (bike lane in-between a through and exclusive right turn lane), was shown to be statistically significant, and although it still had a positive correlation with injury risk, it had a much lower risk of crashes than a typical bike lane at intersections. The presence of a far shared path (more than 4 feet from the edge of curb) was shown to be statistically significant in decreasing the risk of crashes between bicycles and motor-vehicles at intersections. Institutional, agricultural, residential, government, and school land uses had positive correlations and were statistically significant with increasing activity of bicyclists at intersections. This study is unique because it uses actual bicycle volume as an exposure to determine the effects of bicycle safety and activity at intersections and not many others have done this. It is important for transportation planners and designers to use this information to design better complete streets in the future.
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Date Issued
2018
Identifier
CFE0007318, ucf:52134
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007318
Transferability and Calibration of the Highway Safety Manual Performance Functions and Development of New Models for Urban four-lane Divided Roads
Title
Transferability and Calibration of the Highway Safety Manual Performance Functions and Development of New Models for Urban four-lane Divided Roads.
Creator
Al Kaaf, Khalid, Abdel-Aty, Mohamed, Oloufa, Amr, Tatari, Omer, Lee, JaeYoung, University of Central Florida
Abstract / Description
Many developing countries have witnessed fast and rapid growth in the last two decades due to the high development rate of economic activity in these countries. Many transportation projects have been constructed. In the same time both population growth and vehicle ownership rate increased; resulting in increasing levels of road crashes. Road traffic crashes in Gulf Cooperation Council (GCC) is considered a serious problem that has deep effects on GCC's population as well as on the national...
Show moreMany developing countries have witnessed fast and rapid growth in the last two decades due to the high development rate of economic activity in these countries. Many transportation projects have been constructed. In the same time both population growth and vehicle ownership rate increased; resulting in increasing levels of road crashes. Road traffic crashes in Gulf Cooperation Council (GCC) is considered a serious problem that has deep effects on GCC's population as well as on the national productivity through the loss of lives, injuries, property damage and the loss of valuable resources. From a recent statistical study of traffic crashes in Oman, it was found that in 2013 there were 7,829 crashes occurred for a total of 1,082,996 registered vehicles. These crashes have resulted in 913, 5591, and 1481 fatal, injury and property damage only crashes, respectively (Directorate General of Traffic, 2014), which is considered high rates of fatalities and injuries compared to other more developed countries. This illustrates the seriousness and dangerousness of the safety situation in GCC countries and Oman particularly. Thus, there is an urgent need to alleviate the Severity of the traffic safety problem in GCC which in turn will set a prime example for other developing countries that face similar problems. Two main data sources from Riyadh, the capital city of Kingdom of Saudi Arabia (KSA) and Muscat, the capital city of Sultanate of Oman have been obtained, processed, and utilized in this study. The Riyadh collision and traffic data for this study were obtained in the form of crash database and GIS maps from two main sources: the Higher Commission for the Development of Riyadh (HCDR) and Riyadh Traffic Department (RTD). The Muscat collision and traffic data were obtained from two main sources: the Muscat Municipality (MM) and Royal Oman Police, Directorate General of Traffic (DGC). Since the ARC GIS is still not used for traffic crash geocoding in Oman, the crash data used in the analysis were extracted manually from the filing system in the DGC.Due to the fact that not all developing countries highway agencies possess sufficient crash data that enable the development of robust models, this problem gives rise to the interest of transferability of many of the models and tools developed in the US and other developed nations. The Highway Safety Manual (HSM) is a prime and comprehensive resource recently developed in the US that would have substantial impact if researchers are able to transfer its models to other similar environment in GCC. It would save time, effort, and money. The first edition of the HSM provides a number of safety performance functions (SPFs), which can be used to predict collisions on a roadway network. This dissertation examined the Transferability of HSM SPFs and developing new local models for Riyadh and Muscat.In this study, first, calibration of the HSM SPFs for Urban Four-lane divided roadway segments (U4D) with angle parking in Riyadh and the development of new SPFs were examined. The study calibrates the HSM SPFs using HSM default Crash Modification Factors (CMFs), then new local CMFs is proposed using cross-sectional method, which treats the estimation of calibration factors using fatal and injury data. In addition, new forms for specific SPFs are further evaluated to identify the best model using the Poisson-Gamma regression technique. To investigate how well the safety performance model fits the data set, several performance measures were examined. The performance measures summarize the differences between the observed and predicted values from related SPFs. Results indicate that the jurisdiction-specific SPFs provided the best fit of the data used in this study, and would be the best SPFs for predicting severe collisions in the City of Riyadh. The study finds that the HSM calibration using Riyadh local CMFs outperforms the calibration method using the HSM default values. The HSM calibration application for Riyadh crash conditions highlights the importance to address variability in reporting thresholds. One of the findings of this research is that, while the medians in this study have oversize widths ranging from 16ft-70ft, median width has insignificant effect on fatal and injury crashes. At the same time the frequent angle parking in Riyadh urban road networks seems to increase the fatal and injury collisions by 52 percent. On the other hand, this dissertation examined the calibration of the HSM SPFs for Urban intersections in Riyadh, Kingdom of Saudi Arabia (KSA) and the development of new set of models using three year of collision data (2004-2006) from the city of Riyadh. Three intersection categories were investigated: 3-leg signalized, 4-leg signalized, and 3-leg unsignalized. In addition, new forms for specific SPFs are further evaluated to identify the best model using the Poisson-Gamma regression technique. Results indicate that the new local developed SPFs provided the best fit of the data used in this study, and would be the best SPFs for predicting severe crashes at urban intersections in the City of RiyadhMoreover, this study examined the calibration of the HSM SPFs for Fatal and Injury (FI), Property Damage Only (PDO) and total crashes for Urban Four-lane divided roadway segments (U4D) in Muscat, Sultanate of Oman and the development of new SPFs. This study first calibrates the HSM SPFs using the HSM methodology, and then new forms for specific SPFs are further evaluated for Muscat's urban roads to identify the best model. Finally, Riyadh fatal and injury model were validated using Muscat FI dataset.Comparisons across the models indicate that HSM calibrated models are superior with a better model fit and would be the best SPFs for predicting collisions in the City of Muscat. The best developed collision model describes the mean crash frequency as a function of natural logarithm of the annual average daily traffic, segment length, and speed limit. The study finds that the differences in road geometric design features and FI collision characteristics between Riyadh and Muscat resulted in an un-transferable Riyadh crash prediction model.Overall, this study lays an important foundation towards the implementation of HSM methods in multiple cities (Riyadh and Muscat), and could help their transportation officials to make informed decisions regarding road safety programs. The implications of the results are extendible to other cities and countries and the region, and perhaps other developing countries as well.
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Date Issued
2014
Identifier
CFE0005452, ucf:50378
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005452
Evaluation and Modeling of the Safety of Open Road Tolling System
Title
Evaluation and Modeling of the Safety of Open Road Tolling System.
Creator
Abuzwidah, Muamer, Abdel-Aty, Mohamed, Radwan, Ahmed, Uddin, Nizam, University of Central Florida
Abstract / Description
The goal of this thesis is to examine the traffic safety impact of upgrading Toll Plazas (TP) to Open Road Tolling (ORT). The ORT could enhance safety but could also pose some traffic safety concerns at Toll plazas. Crashes from eight years were investigated by evaluating the crash data before and after the implementation of the ORT.The study was conducted by using two approaches: 1) a simple before and after study and with a comparison group; 2) a modeling effort to help understand the...
Show moreThe goal of this thesis is to examine the traffic safety impact of upgrading Toll Plazas (TP) to Open Road Tolling (ORT). The ORT could enhance safety but could also pose some traffic safety concerns at Toll plazas. Crashes from eight years were investigated by evaluating the crash data before and after the implementation of the ORT.The study was conducted by using two approaches: 1) a simple before and after study and with a comparison group; 2) a modeling effort to help understand the relationship between the crash frequency and several important factors and circumstances such as injury severity, collision types, average daily traffic (ADT) and Toll plaza characteristics. The study investigated 11 Toll plazas on State Roads 408, 417, 528 and 429 that have been changed to the ORT design. Several maps showing the Toll plazas and identifying the relevant crash locations were generated. Negative Binomial (NB), Log Linear model and two-way contingency table were examined. Two log-linear models with three variables in each model with all possible two-way interactions were developed. Categorical data analysis of the 2009 and 2010 crash dataset was performed. In order to compare the differences in response between the crash frequency and a particular crash-related variable, odds ratios were computed. The effects of crash frequency and crash-related factors were examined, and interactions among them were considered. The results indicated significant relationships between the crash frequency and ADT, crash type and driver age.It is worth mentioning that the expressway network understudy was continuously experiencing constructions throughout the study period. There is indication that ORT reduced the total crash number; also there is indication of changing the crash types and locations; and the majority of crashes occurred at the diverging and merging areas and resulted in more severe crashes. More data may be needed to confirm these results especially after all constructions and upgrades are made.The Implementation of open road tolling, the locations of Toll plazas, Automatic Vehicle Identification (AVI) subscription rate, traffic demand, and plaza geometry all may have a high influence on traffic safety concerns at Toll plazas, as concluded from the negative Binomial Model's results. The changing of sign locations, reducing the speed limit, installing variable message signs, configuring plazas properly, and other considerations may be the solution to overcome the potential safety problems in the vicinity of Toll plazas.The change of design to ORT was proven to be an excellent solution to several traffic operation problems, including reducing congestion and improving traffic flow and capacity at Toll plazas. However, addressing safety concerns at Toll plazas should take priority.
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Date Issued
2011
Identifier
CFE0004466, ucf:49330
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004466
Pedestrian Safety Analysis through Effective Exposure Measures and Examination of Injury Severity
Title
Pedestrian Safety Analysis through Effective Exposure Measures and Examination of Injury Severity.
Creator
Shah, Md Imran, Abdel-Aty, Mohamed, Eluru, Naveen, Lee, JaeYoung, University of Central Florida
Abstract / Description
Pedestrians are considered the most vulnerable road users who are directly exposed to traffic crashes. In 2014, there were 4,884 pedestrians killed and 65,000 injured in the United States. Pedestrian safety is a growing concern in the development of sustainable transportation system. But often it is found that safety analysis suffers from lack of accurate pedestrian trip information. In such cases, determining effective exposure measures is the most appropriate safety analysis approach. Also...
Show morePedestrians are considered the most vulnerable road users who are directly exposed to traffic crashes. In 2014, there were 4,884 pedestrians killed and 65,000 injured in the United States. Pedestrian safety is a growing concern in the development of sustainable transportation system. But often it is found that safety analysis suffers from lack of accurate pedestrian trip information. In such cases, determining effective exposure measures is the most appropriate safety analysis approach. Also it is very important to clearly understand the relationship between pedestrian injury severity and the factors contributing to higher injury severity. Accurate safety analysis can play a vital role in the development of appropriate safety countermeasures and policies for pedestrians.Since pedestrian volume data is the most important information in safety analysis but rarely available, the first part of the study aims at identifying surrogate measures for pedestrian exposure at intersections. A two-step process is implemented: the first step is the development of Tobit and Generalized Linear Models for predicting pedestrian trips (i.e., exposure models). In the second step, Negative Binomial and Zero Inflated Negative Binomial crash models were developed using the predicted pedestrian trips. The results indicate that among various exposure models the Tobit model performs the best in describing pedestrian exposure. The identified exposure relevant factors are the presence of schools, car-ownership, pavement condition, sidewalk width, bus ridership, intersection control type and presence of sidewalk barrier. The t-test and Wilcoxon signed-rank test results show that there is no significant difference between the observed and the predicted pedestrian trips. The process implemented can help in estimating reliable safety performance functions even when pedestrian trip data is unavailable.The second part of the study focuses on analyzing pedestrian injury severity for the nine counties in Central Florida. The study region covers the Orlando area which has the second-worst pedestrian death rate in the country. Since the dependent variable 'Injury' is ordinal, an 'Ordered Logit' model was developed to identify the factors of pedestrian injury severity. The explanatory variables can be classified as pedestrian/driver characteristics (e.g., age, gender, etc.), roadway traffic and geometric conditions (e.g.: shoulder presence, roadway speed etc.) and crash environment (e.g., light, road surface, work zone, etc.) characteristics. The results show that drug/alcohol involvement, pedestrians in a hurry, roadway speed limit 40 mph or more, dark condition (lighted and unlighted) and presence of elder pedestrians are the primary contributing factors of severe pedestrian crashes in Central Florida. Crashes within the presence of intersections and local roads result in lower injury severity. The area under the ROC (Receiver Operating Characteristic) curve has a value of 0.75 that indicates the model performs reasonably well. Finally the study validated the model using k-fold cross validation method. The results could be useful for transportation officials for further pedestrian safety analysis and taking the appropriate safety interventions.Walking is cost-effective, environmentally friendly and possesses significant health benefits. In order to get these benefits from walking, the most important task is to ensure safer roads for pedestrians.
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Date Issued
2017
Identifier
CFE0006656, ucf:51224
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006656
Examining Multiple Approaches for the Transferability of Safety Performance Functions
Title
Examining Multiple Approaches for the Transferability of Safety Performance Functions.
Creator
Farid, Ahmed Tarek Ahmed, Abdel-Aty, Mohamed, Lee, JaeYoung, Eluru, Naveen, University of Central Florida
Abstract / Description
Safety performance functions (SPFs) are essential in road safety since they are used to predict crash frequencies. They are commonly applied for detecting hot spots in network screening and assessing whether road safety countermeasures are effective. In the Highway Safety Manual (HSM), SPFs are provided for several crash classifications for several types of roadway facilities. The SPFs of the HSM are developed using data from multiple states. In regions where jurisdiction specific SPFs are...
Show moreSafety performance functions (SPFs) are essential in road safety since they are used to predict crash frequencies. They are commonly applied for detecting hot spots in network screening and assessing whether road safety countermeasures are effective. In the Highway Safety Manual (HSM), SPFs are provided for several crash classifications for several types of roadway facilities. The SPFs of the HSM are developed using data from multiple states. In regions where jurisdiction specific SPFs are not available, it is custom to adopt nationwide SPFs for crash predictions then apply a calibration factor. Yet, the research is limited regarding the application of national SPFs for local jurisdictions. In this study, the topic of transferability is explored by examining rural multilane highway SPFs from Florida, Ohio, and California. That is for both divided segments and intersections. Traffic, road geometrics and crash data from the three states are collected to develop one-state, two-state and three-state SPFs. The SPFs are negative binomial models taking the form of those of the HSM. Evaluation of the transferability of models is undertaken by calculating a measure known as the transfer index. It is used to explain which SPFs may be transferred tolerably to other jurisdictions. According to the results, the transferability of rural divided segments' SPFs of Florida to California and vice versa is superior to that of Ohio's SPFs. For four-leg signalized intersections, neither state's models are transferable to any state. Also, the transfer index indicates improved transferability when using pooled data from multiple states. Furthermore, a modified version of the Empirical Bayes method that is responsible for segment specific adjustment factors is proposed as an alternative to the HSM calibration method. It is used to adjust crash frequencies predicted by the SPFs being transferred to the jurisdiction of interest. The modified method, proposed, outperforms the HSM calibration method as per the analysis results.
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Date Issued
2015
Identifier
CFE0006298, ucf:51604
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006298