Praveena Penmetsa | University of Alabama - Tuscaloosa (original) (raw)

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Papers by Praveena Penmetsa

Research paper thumbnail of Modeling crash injury severity by road feature to improve safety

Traffic Injury Prevention

The objective of this research is 2-fold: to (a) model and identify critical road features (or lo... more The objective of this research is 2-fold: to (a) model and identify critical road features (or locations) based on crash injury severity and compare it with crash frequency and (b) model and identify drivers who are more likely to contribute to crashes by road feature. Crash data from 2011 to 2013 were obtained from the Highway Safety Information System (HSIS) for the state of North Carolina. Twenty-three different road features were considered, analyzed, and compared with each other as well as no road feature. A multinomial logit (MNL) model was developed and odds ratios were estimated to investigate the effect of road features on crash injury severity. Among the many road features, underpass, end or beginning of a divided highway, and on-ramp terminal on crossroad are the top 3 critical road features. Intersection crashes are frequent but are not highly likely to result in severe injuries compared to critical road features. Roundabouts are least likely to result in both severe and moderate injuries. Female drivers are more likely to be involved in crashes at intersections (4-way and T) compared to male drivers. Adult drivers are more likely to be involved in crashes at underpasses. Older drivers are 1.6 times more likely to be involved in a crash at the end or beginning of a divided highway. The findings from this research help to identify critical road features that need to be given priority. As an example, additional advanced warning signs and providing enlarged or highly retroreflective signs that grab the attention of older drivers may help in making locations such as end or beginning of a divided highway much safer. Educating drivers about the necessary skill sets required at critical road features in addition to engineering solutions may further help them adopt safe driving behaviors on the road.

Research paper thumbnail of Risk Drivers Pose to Themselves and Other Drivers by Violating Traffic Rules

Traffic Injury Prevention, 2016

Violation of traffic rules is a major contributing factor in both crashes and fatalities in the U... more Violation of traffic rules is a major contributing factor in both crashes and fatalities in the United States. This study aims at quantifying risk that drivers pose to themselves and other drivers by violating traffic rules. Crash data from 2010 to 2013 were gathered for the state of North Carolina. Descriptive analysis was carried out to identify frequent traffic violations and who were committing the traffic violations that resulted in crashes. A multinomial logit model was then developed to examine the relation between different traffic violations and driver injury severity. Additionally, odds ratios were estimated to identify the likelihood (probability) of severe or moderate injury to the driver and other drivers due to a driver violating a traffic rule that led to a crash. Exceeding the speed limit is more likely to result in severe injury compared to disregarding traffic signals. However, going the wrong way is more likely to result in severe injury to other drivers when compared to any other traffic violation. Driving under the influence of alcohol is 2 times more likely to result in severe injury than driving under the influence of drugs. These 2 traffic violations by a driver are almost equally likely to result in severe injury to other drivers. Drivers often perceive that violating traffic rules will not result in a crash or severe injury. However, the results from this study show that a majority of the traffic violations lead to severe injury to the violator as well as to other drivers. The findings from this study serve as documented evidence to educate drivers about the risk they pose to themselves and to other drivers by violating traffic rules and encourage the adaptation of safe driving behavior in order to contribute toward reaching the "zero traffic deaths" vision. They also help make policy changes pertaining to penalty points and fines for violating a traffic rule.

Research paper thumbnail of Monetary Value of Travel Time Reliability and Thresholds Based on Random Participants Perceptions

The value of travel time refers to the monetary value travelers place on their travel time or in ... more The value of travel time refers to the monetary value travelers place on their travel time or in reducing their travel time. On the other hand, the value of reliability connects the monetary value travelers place on reducing travel time variations. Defining monetary value of reliability and thresholds is challenging unlike travel time savings and estimated average hourly rates to assess impacts and evaluate transportation projects / alternatives. The focus of this paper is on monetizing travel time reliability and identifying thresholds to evaluate transportation projects / alternatives. A stated preference survey was conducted to randomly gather perceptions of participants, monetize reliability and identify reliability thresholds. Results indicate that 60.8% of the random survey participants were willing to take an unreliable route with a maximum travel time of 30 minutes, while only 25.5% of the random survey participants were willing to take an unreliable route with a maximum travel time of 40 minutes (instead of the reliable route). Similarly, 60.8% of the random survey participants were willing to take an unreliable route with up to two days of the lack of reliability per month. On the other hand, only 33.8% of the random survey participants were willing to take an unreliable route with up to four days of the lack of reliability per month. Overall, the generalized value of buffer time from the random general survey is estimated equal to $0.45 per minute. Differences in the value of buffer time were observed between cities, towns and other areas

Research paper thumbnail of Risk Perceptions of Drivers: Does It Change with Crash History or Prior Convictions?

This paper examines whether risk perceptions of drivers towards a traffic rule violation change w... more This paper examines whether risk perceptions of drivers towards a traffic rule violation change with prior crash history or prior violations history. The data from the Naturalistic Driving Study (NDS), consisting of several surveys answered by voluntarily participated drivers across the United States, was used for research and analysis. The change in risk perception of participants is generally significant with involvement in two or more crashes. Participants between 16 to 19 years had a significant increase in the risk perception after involving in an injury severity crash. Participants between 16 to 19 years who were found at fault in a crash had significantly less risk perception than participants of the same age group who were not found at fault in a crash. Similarly, participants between 45 to 54 years had a significant change in the risk perceptions, but participants who were found at fault had high risk perceptions than who were not found at fault. Participants above 55 years and who were involved in injury severity crash found traffic rule violations less risky than participants of the same age group who were involved in damage only but not reported crashes. Overall, the results from this study help in understanding how drivers risk perceptions change after involving in crashes or convicted of violations. They assist in better educating drivers to increase the risk perceptions towards traffic rule violations so as to improve safety on roads.

Research paper thumbnail of RISK DRIVERS POSE TO THEMSELVES DUE TO TRAFFIC VIOLATIONS

Objective: Violation of traffic rules is a major contributing factor of both crashes and fataliti... more Objective: Violation of traffic rules is a major contributing factor of both crashes and fatalities in the United States. This study aims at examining crashes due to traffic violations and quantifying risk drivers pose to themselves by violating traffic rules.
Method: The crash data from 2009 to 2011 was collected for the entire state of North Carolina. Descriptive statistics was carried out to identify who were committing the traffic violations that resulted in crashes. Multinomial regression model was then developed to examine the relation between different traffic violations and driver injury severity. Additionally, odds ratio was estimated to identify the likelihood (probability) of severe or moderate injury to the driver after committing a traffic violation that led to a crash.
Results: Exceeding speed limit is 182 times more likely to result in severe driver injuries compared to driver injury in no traffic violation crashes. Passing on a curve (in no passing zones), driving under the influence of alcohol, going in wrong way, and aggressive driving are approximately 50 times more likely to result in severe driver injury. Disregarding stop sign is 20 and 4 times more likely to result in severe injury and moderate injury to the driver, respectively. Overall, most of the crashes that occurred due to traffic violations result in severe driver injuries.
Conclusions: Often times, drivers perceive that violating traffic rules does not result in a crash or severe injuries. However, the results from this study show that a majority of the traffic violations lead to severe driver injury. The findings from this study serve as documented evidence to educate drivers about the risk they pose to themselves by violating traffic rules and encourage adaptation of safe driving behavior in order to contribute towards reaching the “zero traffic deaths” vision.

Research paper thumbnail of Methods to Rank Traffic Rule Violations Resulting in Crashes for Allocation of Funds

Education, enforcement and engineering countermeasures are implemented to make road users comply ... more Education, enforcement and engineering countermeasures are implemented to make road users comply with the traffic rules. Not all traffic rule violations can be addressed nor countermeasures implemented at all unsafe locations, at once, due to limited funds. Therefore, it is important to identify as well as rank traffic rule violations that should be given priority in addition to where to allocate funds so as to maximize derived benefits. This study aims at ranking traffic rule violations resulting in crashes based on individual methods such as 1) severity, 2) frequency, 3) total crash cost, and, 4) cost severity index to assist transportation system managers in prioritizing the allocation of funds and improving safety. Crash data gathered for the state of North Carolina was used in this study. Variations in the ranks of traffic rule violations were observed when individual methods are used. As an example, driving under the influence of alcohol and going wrong way/crossing center-line are ranked 1st and 2nd based on severity of the crash while failure to reduce speed and failing to yield the right-of-way are ranked 1st and 2nd based on frequency. As the individual methods have their own merits and demerits, four different sum of ranks methods were developed and evaluated to rank and prioritize the traffic rule violations. The critical top ranked traffic rule violations remain the same irrespective of the considered sum of ranks method. The sum of ranks methods based on severity and frequency or frequency and cost severity index is recommended for prioritization and allocation of funds.

Research paper thumbnail of FACTORS ASSOCIATED WITH CRASHES DUE TO OVERCORRECTION OR OVERSTEERING OF VEHICLES

The objective of this research is to identify factors associated with crashes due to overcorrecti... more The objective of this research is to identify factors associated with crashes due to overcorrection or oversteering of vehicles. Crash data was collected from 2011 to 2013 for the State of North Carolina in the United States. Logistic regression was used to analyze crash data because of the dichotomous nature of the dependent variable (overcorrection or oversteering). The crash involvement due to overcorrection or oversteering of a vehicle decreased as the age of the driver increased. Drivers are 2.33 times as likely to overcorrect or oversteer when ill, 3.48 times as likely to overcorrect or oversteer when under fatigue, and 1.85 times as likely to overcorrect or oversteer when fallen asleep compared to normal physical conditions. Overall, driver characteristics and speed limit tend to play a major role in overcorrection or oversteering of vehicles. Programs to reduce impaired driving might help in the reduction of overcorrection or oversteering related crash fatalities or injuries. Additionally, training and driver education programs focusing on identified factors associated with crashes due to overcorrection or oversteering of vehicles will benefit drivers on how to respond during emergency or panic situations.

Research paper thumbnail of Evaluating the Feasibility of Imposing Restriction on the Use of Older Vehicles

Reducing the number of vehicles on roads as well as those that contribute to high levels of emiss... more Reducing the number of vehicles on roads as well as those that contribute to high levels of emissions and fuel consumption improves air quality and makes our world more sustainable. One possible solution to address these goals is to restrict or at least discourage the use of older vehicles (20 or more years old). The lack of access to alternate modes, however, may deprive some of the older vehicle users to efficiently commute from one point to another point in the transportation network. The objectives of this study are to identify who are using older vehicles, examine whether the older vehicle users have access to public transportation for longer commutes, and to evaluate the feasibility of imposing restrictions on using older vehicles. Random survey followed by the development of ordered logit model and geospatial analysis was used to perform evaluations and assess the outcomes. The results obtained show that population with income less than $25,000 is more likely to possess older vehicles in North Carolina. About 36% of low-income population does not have access to a bus stop and may have to relocate closer to a bus stop or buy a relatively newer vehicle. Beyond 10 miles from the Charlotte city center, not more than 20% of the population has access to a bus stop in 95% of the census blocks. This indicates how vulnerable the low-income group would be, deprived of efficient longer commutes or travel options, if restrictions are currently imposed on the usage of older vehicles

Research paper thumbnail of Risk Factors Attributed to Fatal Fixed Object Crashes on Non-Interstate Roads

This study aims at identifying risk factors attributed to fatal fixed object crashes on non-inter... more This study aims at identifying risk factors attributed to fatal fixed object crashes on non-interstate roads. Logistic regression model was used to understand the relation or extent of the effect of different independent variables on fatal fixed object crashes on non-interstate roads. A total of 30 independent variables were considered in this study. At a 95% confidence interval, nine independent variables were found to play a statistically significant role on fatal fixed object crashes on non-interstate roads. The probability of getting involved in a fatal fixed object crash on full access control non-interstate roads is lower compared to no access control non-interstate roads. Rolling terrain reduces the probability of getting involved in a non-interstate fatal fixed object crash. Older drivers are more likely to be killed in a non-interstate fatal fixed object crash. Drivers under the influence of alcohol have four times higher probability of being killed in a non-interstate fatal fixed object crash compared to a sober driver. The findings from this study provide adequate evidence and assist traffic engineers and policy makers to better understand the role of risk factors and identify suitable countermeasures to reduce fatal fixed object crashes specifically on non-interstate roads.

Research paper thumbnail of Examining the Effect of Road Features on Crash Injury Severity

The objective of this study is two-fold; a) to investigate the effects of road features (or locat... more The objective of this study is two-fold; a) to investigate the effects of road features (or locations) on injury severity and compare it with crash frequency, and, b) to identify drivers who are more likely to contribute to crashes at certain road features. Crash data from 2011 to 2013 was collected from Highway Safety Information System (HSIS) for the state of North Carolina. A total of 23 different road features were considered, analyzed and compared with no road features. Multinomial logit model was developed and odds ratios were estimated to investigate the effects of road features on injury severity. Among the many road features, underpass, end or beginning of a divided highway, and on-ramp terminal on crossroad are the top three critical road features. Intersection crashes are frequent but not highly likely to result in severe injuries compared to the aforementioned critical road features. Roundabouts are least likely to result in both severe and moderate injuries. Female drivers are more likely to involve in crashes at intersections (four-way and T) compared to male drivers. Adult drivers are highly likely to be involved in crashes at underpasses. Older drivers are 1.6 times more likely to crash at the end or beginning of a divided highway. Providing signs that grab the attention of the older drivers will help in making this location much safer. Overall, the findings help identify road features that need to be given priority. Educating drivers about the necessary skill sets required at critical road features will further help them adopt safe driving behavior on roads.

Research paper thumbnail of Evaluation of Performance Measures for Two-Lane Inter-urban Highways under Mixed Traffic Condition

The traffic performance of a highway is expressed in terms of level of service (LOS). It is a maj... more The traffic performance of a highway is expressed in terms of level of service (LOS). It is a major input to important decisions on public fund investments that are made at different stages of the highway life. Because of its unique operational characteristics the evaluation of traffic performance on two-lane highways is not an easy task. The objectives of this research are (a) to examine the applicability of various performance measures for two-lane highways under mixed traffic conditions (b) to assign threshold values for different levels of service based on the best performance measure observed. Graphical and statistical analysis are carried out among the six most popular performance measures and traffic volume. No measure was found reliable for mixed traffic conditions. Therefore, the number of followers (NF) was introduced as a new performance measure. In mixed traffic conditions, followers are defined as vehicles travelling with gap less than 2.5s. Although NF is found to have good correlation with flow rate, it was also not able to reflect the true congestion conditions of a roadway. Therefore, this parameter is further modified to number of followers as a proportion of capacity (NFPC). It demonstrated a very strong correlation with traffic volume. Threshold values are proposed for different LOS based on NFPC for mixed traffic conditions.

Research paper thumbnail of Modeling crash injury severity by road feature to improve safety

Traffic Injury Prevention

The objective of this research is 2-fold: to (a) model and identify critical road features (or lo... more The objective of this research is 2-fold: to (a) model and identify critical road features (or locations) based on crash injury severity and compare it with crash frequency and (b) model and identify drivers who are more likely to contribute to crashes by road feature. Crash data from 2011 to 2013 were obtained from the Highway Safety Information System (HSIS) for the state of North Carolina. Twenty-three different road features were considered, analyzed, and compared with each other as well as no road feature. A multinomial logit (MNL) model was developed and odds ratios were estimated to investigate the effect of road features on crash injury severity. Among the many road features, underpass, end or beginning of a divided highway, and on-ramp terminal on crossroad are the top 3 critical road features. Intersection crashes are frequent but are not highly likely to result in severe injuries compared to critical road features. Roundabouts are least likely to result in both severe and moderate injuries. Female drivers are more likely to be involved in crashes at intersections (4-way and T) compared to male drivers. Adult drivers are more likely to be involved in crashes at underpasses. Older drivers are 1.6 times more likely to be involved in a crash at the end or beginning of a divided highway. The findings from this research help to identify critical road features that need to be given priority. As an example, additional advanced warning signs and providing enlarged or highly retroreflective signs that grab the attention of older drivers may help in making locations such as end or beginning of a divided highway much safer. Educating drivers about the necessary skill sets required at critical road features in addition to engineering solutions may further help them adopt safe driving behaviors on the road.

Research paper thumbnail of Risk Drivers Pose to Themselves and Other Drivers by Violating Traffic Rules

Traffic Injury Prevention, 2016

Violation of traffic rules is a major contributing factor in both crashes and fatalities in the U... more Violation of traffic rules is a major contributing factor in both crashes and fatalities in the United States. This study aims at quantifying risk that drivers pose to themselves and other drivers by violating traffic rules. Crash data from 2010 to 2013 were gathered for the state of North Carolina. Descriptive analysis was carried out to identify frequent traffic violations and who were committing the traffic violations that resulted in crashes. A multinomial logit model was then developed to examine the relation between different traffic violations and driver injury severity. Additionally, odds ratios were estimated to identify the likelihood (probability) of severe or moderate injury to the driver and other drivers due to a driver violating a traffic rule that led to a crash. Exceeding the speed limit is more likely to result in severe injury compared to disregarding traffic signals. However, going the wrong way is more likely to result in severe injury to other drivers when compared to any other traffic violation. Driving under the influence of alcohol is 2 times more likely to result in severe injury than driving under the influence of drugs. These 2 traffic violations by a driver are almost equally likely to result in severe injury to other drivers. Drivers often perceive that violating traffic rules will not result in a crash or severe injury. However, the results from this study show that a majority of the traffic violations lead to severe injury to the violator as well as to other drivers. The findings from this study serve as documented evidence to educate drivers about the risk they pose to themselves and to other drivers by violating traffic rules and encourage the adaptation of safe driving behavior in order to contribute toward reaching the "zero traffic deaths" vision. They also help make policy changes pertaining to penalty points and fines for violating a traffic rule.

Research paper thumbnail of Monetary Value of Travel Time Reliability and Thresholds Based on Random Participants Perceptions

The value of travel time refers to the monetary value travelers place on their travel time or in ... more The value of travel time refers to the monetary value travelers place on their travel time or in reducing their travel time. On the other hand, the value of reliability connects the monetary value travelers place on reducing travel time variations. Defining monetary value of reliability and thresholds is challenging unlike travel time savings and estimated average hourly rates to assess impacts and evaluate transportation projects / alternatives. The focus of this paper is on monetizing travel time reliability and identifying thresholds to evaluate transportation projects / alternatives. A stated preference survey was conducted to randomly gather perceptions of participants, monetize reliability and identify reliability thresholds. Results indicate that 60.8% of the random survey participants were willing to take an unreliable route with a maximum travel time of 30 minutes, while only 25.5% of the random survey participants were willing to take an unreliable route with a maximum travel time of 40 minutes (instead of the reliable route). Similarly, 60.8% of the random survey participants were willing to take an unreliable route with up to two days of the lack of reliability per month. On the other hand, only 33.8% of the random survey participants were willing to take an unreliable route with up to four days of the lack of reliability per month. Overall, the generalized value of buffer time from the random general survey is estimated equal to $0.45 per minute. Differences in the value of buffer time were observed between cities, towns and other areas

Research paper thumbnail of Risk Perceptions of Drivers: Does It Change with Crash History or Prior Convictions?

This paper examines whether risk perceptions of drivers towards a traffic rule violation change w... more This paper examines whether risk perceptions of drivers towards a traffic rule violation change with prior crash history or prior violations history. The data from the Naturalistic Driving Study (NDS), consisting of several surveys answered by voluntarily participated drivers across the United States, was used for research and analysis. The change in risk perception of participants is generally significant with involvement in two or more crashes. Participants between 16 to 19 years had a significant increase in the risk perception after involving in an injury severity crash. Participants between 16 to 19 years who were found at fault in a crash had significantly less risk perception than participants of the same age group who were not found at fault in a crash. Similarly, participants between 45 to 54 years had a significant change in the risk perceptions, but participants who were found at fault had high risk perceptions than who were not found at fault. Participants above 55 years and who were involved in injury severity crash found traffic rule violations less risky than participants of the same age group who were involved in damage only but not reported crashes. Overall, the results from this study help in understanding how drivers risk perceptions change after involving in crashes or convicted of violations. They assist in better educating drivers to increase the risk perceptions towards traffic rule violations so as to improve safety on roads.

Research paper thumbnail of RISK DRIVERS POSE TO THEMSELVES DUE TO TRAFFIC VIOLATIONS

Objective: Violation of traffic rules is a major contributing factor of both crashes and fataliti... more Objective: Violation of traffic rules is a major contributing factor of both crashes and fatalities in the United States. This study aims at examining crashes due to traffic violations and quantifying risk drivers pose to themselves by violating traffic rules.
Method: The crash data from 2009 to 2011 was collected for the entire state of North Carolina. Descriptive statistics was carried out to identify who were committing the traffic violations that resulted in crashes. Multinomial regression model was then developed to examine the relation between different traffic violations and driver injury severity. Additionally, odds ratio was estimated to identify the likelihood (probability) of severe or moderate injury to the driver after committing a traffic violation that led to a crash.
Results: Exceeding speed limit is 182 times more likely to result in severe driver injuries compared to driver injury in no traffic violation crashes. Passing on a curve (in no passing zones), driving under the influence of alcohol, going in wrong way, and aggressive driving are approximately 50 times more likely to result in severe driver injury. Disregarding stop sign is 20 and 4 times more likely to result in severe injury and moderate injury to the driver, respectively. Overall, most of the crashes that occurred due to traffic violations result in severe driver injuries.
Conclusions: Often times, drivers perceive that violating traffic rules does not result in a crash or severe injuries. However, the results from this study show that a majority of the traffic violations lead to severe driver injury. The findings from this study serve as documented evidence to educate drivers about the risk they pose to themselves by violating traffic rules and encourage adaptation of safe driving behavior in order to contribute towards reaching the “zero traffic deaths” vision.

Research paper thumbnail of Methods to Rank Traffic Rule Violations Resulting in Crashes for Allocation of Funds

Education, enforcement and engineering countermeasures are implemented to make road users comply ... more Education, enforcement and engineering countermeasures are implemented to make road users comply with the traffic rules. Not all traffic rule violations can be addressed nor countermeasures implemented at all unsafe locations, at once, due to limited funds. Therefore, it is important to identify as well as rank traffic rule violations that should be given priority in addition to where to allocate funds so as to maximize derived benefits. This study aims at ranking traffic rule violations resulting in crashes based on individual methods such as 1) severity, 2) frequency, 3) total crash cost, and, 4) cost severity index to assist transportation system managers in prioritizing the allocation of funds and improving safety. Crash data gathered for the state of North Carolina was used in this study. Variations in the ranks of traffic rule violations were observed when individual methods are used. As an example, driving under the influence of alcohol and going wrong way/crossing center-line are ranked 1st and 2nd based on severity of the crash while failure to reduce speed and failing to yield the right-of-way are ranked 1st and 2nd based on frequency. As the individual methods have their own merits and demerits, four different sum of ranks methods were developed and evaluated to rank and prioritize the traffic rule violations. The critical top ranked traffic rule violations remain the same irrespective of the considered sum of ranks method. The sum of ranks methods based on severity and frequency or frequency and cost severity index is recommended for prioritization and allocation of funds.

Research paper thumbnail of FACTORS ASSOCIATED WITH CRASHES DUE TO OVERCORRECTION OR OVERSTEERING OF VEHICLES

The objective of this research is to identify factors associated with crashes due to overcorrecti... more The objective of this research is to identify factors associated with crashes due to overcorrection or oversteering of vehicles. Crash data was collected from 2011 to 2013 for the State of North Carolina in the United States. Logistic regression was used to analyze crash data because of the dichotomous nature of the dependent variable (overcorrection or oversteering). The crash involvement due to overcorrection or oversteering of a vehicle decreased as the age of the driver increased. Drivers are 2.33 times as likely to overcorrect or oversteer when ill, 3.48 times as likely to overcorrect or oversteer when under fatigue, and 1.85 times as likely to overcorrect or oversteer when fallen asleep compared to normal physical conditions. Overall, driver characteristics and speed limit tend to play a major role in overcorrection or oversteering of vehicles. Programs to reduce impaired driving might help in the reduction of overcorrection or oversteering related crash fatalities or injuries. Additionally, training and driver education programs focusing on identified factors associated with crashes due to overcorrection or oversteering of vehicles will benefit drivers on how to respond during emergency or panic situations.

Research paper thumbnail of Evaluating the Feasibility of Imposing Restriction on the Use of Older Vehicles

Reducing the number of vehicles on roads as well as those that contribute to high levels of emiss... more Reducing the number of vehicles on roads as well as those that contribute to high levels of emissions and fuel consumption improves air quality and makes our world more sustainable. One possible solution to address these goals is to restrict or at least discourage the use of older vehicles (20 or more years old). The lack of access to alternate modes, however, may deprive some of the older vehicle users to efficiently commute from one point to another point in the transportation network. The objectives of this study are to identify who are using older vehicles, examine whether the older vehicle users have access to public transportation for longer commutes, and to evaluate the feasibility of imposing restrictions on using older vehicles. Random survey followed by the development of ordered logit model and geospatial analysis was used to perform evaluations and assess the outcomes. The results obtained show that population with income less than $25,000 is more likely to possess older vehicles in North Carolina. About 36% of low-income population does not have access to a bus stop and may have to relocate closer to a bus stop or buy a relatively newer vehicle. Beyond 10 miles from the Charlotte city center, not more than 20% of the population has access to a bus stop in 95% of the census blocks. This indicates how vulnerable the low-income group would be, deprived of efficient longer commutes or travel options, if restrictions are currently imposed on the usage of older vehicles

Research paper thumbnail of Risk Factors Attributed to Fatal Fixed Object Crashes on Non-Interstate Roads

This study aims at identifying risk factors attributed to fatal fixed object crashes on non-inter... more This study aims at identifying risk factors attributed to fatal fixed object crashes on non-interstate roads. Logistic regression model was used to understand the relation or extent of the effect of different independent variables on fatal fixed object crashes on non-interstate roads. A total of 30 independent variables were considered in this study. At a 95% confidence interval, nine independent variables were found to play a statistically significant role on fatal fixed object crashes on non-interstate roads. The probability of getting involved in a fatal fixed object crash on full access control non-interstate roads is lower compared to no access control non-interstate roads. Rolling terrain reduces the probability of getting involved in a non-interstate fatal fixed object crash. Older drivers are more likely to be killed in a non-interstate fatal fixed object crash. Drivers under the influence of alcohol have four times higher probability of being killed in a non-interstate fatal fixed object crash compared to a sober driver. The findings from this study provide adequate evidence and assist traffic engineers and policy makers to better understand the role of risk factors and identify suitable countermeasures to reduce fatal fixed object crashes specifically on non-interstate roads.

Research paper thumbnail of Examining the Effect of Road Features on Crash Injury Severity

The objective of this study is two-fold; a) to investigate the effects of road features (or locat... more The objective of this study is two-fold; a) to investigate the effects of road features (or locations) on injury severity and compare it with crash frequency, and, b) to identify drivers who are more likely to contribute to crashes at certain road features. Crash data from 2011 to 2013 was collected from Highway Safety Information System (HSIS) for the state of North Carolina. A total of 23 different road features were considered, analyzed and compared with no road features. Multinomial logit model was developed and odds ratios were estimated to investigate the effects of road features on injury severity. Among the many road features, underpass, end or beginning of a divided highway, and on-ramp terminal on crossroad are the top three critical road features. Intersection crashes are frequent but not highly likely to result in severe injuries compared to the aforementioned critical road features. Roundabouts are least likely to result in both severe and moderate injuries. Female drivers are more likely to involve in crashes at intersections (four-way and T) compared to male drivers. Adult drivers are highly likely to be involved in crashes at underpasses. Older drivers are 1.6 times more likely to crash at the end or beginning of a divided highway. Providing signs that grab the attention of the older drivers will help in making this location much safer. Overall, the findings help identify road features that need to be given priority. Educating drivers about the necessary skill sets required at critical road features will further help them adopt safe driving behavior on roads.

Research paper thumbnail of Evaluation of Performance Measures for Two-Lane Inter-urban Highways under Mixed Traffic Condition

The traffic performance of a highway is expressed in terms of level of service (LOS). It is a maj... more The traffic performance of a highway is expressed in terms of level of service (LOS). It is a major input to important decisions on public fund investments that are made at different stages of the highway life. Because of its unique operational characteristics the evaluation of traffic performance on two-lane highways is not an easy task. The objectives of this research are (a) to examine the applicability of various performance measures for two-lane highways under mixed traffic conditions (b) to assign threshold values for different levels of service based on the best performance measure observed. Graphical and statistical analysis are carried out among the six most popular performance measures and traffic volume. No measure was found reliable for mixed traffic conditions. Therefore, the number of followers (NF) was introduced as a new performance measure. In mixed traffic conditions, followers are defined as vehicles travelling with gap less than 2.5s. Although NF is found to have good correlation with flow rate, it was also not able to reflect the true congestion conditions of a roadway. Therefore, this parameter is further modified to number of followers as a proportion of capacity (NFPC). It demonstrated a very strong correlation with traffic volume. Threshold values are proposed for different LOS based on NFPC for mixed traffic conditions.