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Dr. AmirArsalan M. Molan
Civil and Environmental Engineering, Cal Poly State University-San Luis Obispo

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0 Highway Safety
0 Traffic Operation Analysis
0 Alternative Intersections
0 Traffic Simulation Modeling
0 Pedestrian and Bicycle Safety

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Journal article
Published: 28 September 2020 in Journal of Safety Research
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Introduction: The main objective of this research is to investigate the effect of traffic barrier geometric characteristics on crashes that occurred on non-interstate roads. Method: For this purpose, height, side-slope rate, post-spacing, and lateral offset of about 137 miles of traffic barriers were collected on non-interstate (state, federal aid primary, federal aid secondary, and federal aid urban) highways in Wyoming. In addition, crash reports recorded between 2008 and 2017 were added to the traffic barrier dataset. The safety performance of traffic barriers with regards to their geometric features was analyzed in terms of crash frequency and crash severity using random-parameters negative binomial, and random-parameters ordered logit models, respectively. Results: From the results, box beam barriers with a height of 27–29 inches were less likely to be associated with injury and fatal injury crashes compared to other barrier types. On the other hand, the likelihood of a severe injury crash was found to be higher for box beam barriers with a height taller than 31 inches. Both W-beam and box beam barriers with a post-spacing between 6.1 and 6.3 inches reduced the probability of severe injury crashes. In terms of the crash frequency, flare traffic barriers had a lower crash frequency compared to parallel traffic barriers. Non-interstate roads without longitudinal rumble strips were associated with a higher rate of traffic barrier crashes.

ACS Style

Amirarsalan Mehrara Molan; Milhan Moomen; Khaled Ksaibati. The impact of traffic barrier geometric features on crash frequency and injury severity of non-interstate highways. Journal of Safety Research 2020, 75, 155 -165.

AMA Style

Amirarsalan Mehrara Molan, Milhan Moomen, Khaled Ksaibati. The impact of traffic barrier geometric features on crash frequency and injury severity of non-interstate highways. Journal of Safety Research. 2020; 75 ():155-165.

Chicago/Turabian Style

Amirarsalan Mehrara Molan; Milhan Moomen; Khaled Ksaibati. 2020. "The impact of traffic barrier geometric features on crash frequency and injury severity of non-interstate highways." Journal of Safety Research 75, no. : 155-165.

Journal article
Published: 06 September 2020 in Simulation Modelling Practice and Theory
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Innovative interchange designs are gaining attention due to their potential in reducing delays and mitigating congestion. This study was aimed at proposing the super diverging diamond interchange (SDDI) as an alternative design to the conventional diamond interchange (CDI), diverging diamond interchange (DDI), diverging partial cloverleaf interchange (DPCI), folded diamond interchange (FDI) and ramp crossover interchange (RCI) designs. An evaluation of the operational performances of the six interchange designs in terms of both vehicular and pedestrian travel times was conducted. The VISSIM micro-simulation software tool was used where several scenarios were proposed and examined. The study was carried out for the E. Mississippi Ave. and I-225 interchange in Aurora, Colorado as part of a project. Note that the interchange, mentioned, is currently operating as a CDI. ANOVA hypothesis tests were conducted to compare the travel times required for both vehicles and pedestrians to navigate each interchange type. The results indicated that, for under-saturated conditions where demand volumes were less than the interchanges’ capacities, implementing either the FDI, SDDI or RCI designs substantially reduced vehicular travel times as opposed to implementing the other designs. On the other hand, for over-saturated conditions in which traffic volumes exceeded capacities, the RCI and FDI exhibited the least vehicular travel times. The CDI was demonstrated to be the most efficient interchange serving pedestrians in all simulated scenarios. It was closely followed by the RCI and SDDI particularly for over-saturated conditions.

ACS Style

Mutasem Alzoubaidi; Amirarsalan Mehrara Molan; Khaled Ksaibati. Comparing the efficiency of the super diverging diamond interchange to other innovative interchanges’. Simulation Modelling Practice and Theory 2020, 106, 102174 .

AMA Style

Mutasem Alzoubaidi, Amirarsalan Mehrara Molan, Khaled Ksaibati. Comparing the efficiency of the super diverging diamond interchange to other innovative interchanges’. Simulation Modelling Practice and Theory. 2020; 106 ():102174.

Chicago/Turabian Style

Mutasem Alzoubaidi; Amirarsalan Mehrara Molan; Khaled Ksaibati. 2020. "Comparing the efficiency of the super diverging diamond interchange to other innovative interchanges’." Simulation Modelling Practice and Theory 106, no. : 102174.

Journal article
Published: 04 August 2020 in International Journal of Transportation Science and Technology
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Reviewing the literature of run-off-road (ROR) crashes, there is limited knowledge in terms of crashes involving side (longitudinal) traffic barriers on curved segments. For instance, despite the valuable results found in past simulation and field crash tests, no study has been conducted using actual crash data analysis to evaluate the safety performance of side traffic barriers on horizontal curves of non-interstate roads. This paper aims to fill this gap. For this purpose, an actual crash data analysis was conducted to identify factors impacting the severity of crashes involving side traffic barriers on horizontal curves of non-interstate roads in Wyoming. A field inventory was conducted to collect type, height, side-slope rate, lateral offset, and post-spacing of over 105 miles of side traffic barriers located on horizontal curves of non-interstate roads in the state of Wyoming. The data collected includes 25% of all traffic barriers (located on tangent and curved segments) on non-interstate roads in Wyoming. Then, the data was combined with historical crashes, road geometric features, and traffic volume data. For the statistical analysis, random-parameters ordered logit was utilized to model the effect of parameters affecting the crash severity. Post-spacing and height of side barriers were identified to be statistically significant on the crash severity on horizontal curves of non-interstate roads. Side box beam barriers with a post-spacing of 6.1 ft were least likely to result in a fatal or severe injury crash. On the other hand, side box beam barriers with a height shorter than 25 inches showed a high probability of fatalities or severe injuries. It was found that ROR crashes tended to be less severe on side W-beam barriers having a height between 24 and 31 inches. Side traffic barriers with a short height are not recommended to be used on horizontal curves. Based on the results found in this research and past similar studies, it is recommended to consider a height taller than recommendations given by the roadside design guide (AASHTO RDG 2011) on curved segments. Post-spacing of 6.1 ft was found to be recommended to be considered for side box beam barriers.

ACS Style

Amirarsalan Mehrara Molan; Khaled Ksaibati. Impact of side traffic barrier features on the severity of run-off-road crashes involving horizontal curves on non-interstate roads. International Journal of Transportation Science and Technology 2020, 1 .

AMA Style

Amirarsalan Mehrara Molan, Khaled Ksaibati. Impact of side traffic barrier features on the severity of run-off-road crashes involving horizontal curves on non-interstate roads. International Journal of Transportation Science and Technology. 2020; ():1.

Chicago/Turabian Style

Amirarsalan Mehrara Molan; Khaled Ksaibati. 2020. "Impact of side traffic barrier features on the severity of run-off-road crashes involving horizontal curves on non-interstate roads." International Journal of Transportation Science and Technology , no. : 1.

Articles
Published: 08 July 2020 in International Journal of Crashworthiness
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Despite numerous past studies conducted on traffic barriers, research is still needed to analyze the performance of traffic barriers on superelevated horizontal curves. Based on the literature of traffic barrier studies, the effect of geometric features of traffic barriers (such as height and post-spacing) on crashes involving horizontal curves has not been investigated considering actual crash data analysis. This paper seeks to study the effect of various variables affecting the severity of traffic barrier crashes on horizontal curves. Geometric features of 95 miles of traffic barriers were collected, conducting a field inventory on all interstate roads in Wyoming. All the traffic barriers collected were located on horizontal curves with at least one historical crash report between 2008 and 2017. Random-parameters ordered logit was used to develop two models to investigate the factors impacting the severity of horizontal curve crashes involving side and median traffic barriers, respectively, on interstate roads. Based on the results, median box beam barriers with a post-spacing of 6.1 ft resulted in lower injury severity. Median W-beam barriers with a height taller than 31 inches were involved with a higher probability of severe collisions. Side box beam barriers located on the front side-slope were also more likely to increase the severity of crashes.

ACS Style

Amirarsalan Mehrara Molan; Sahima Nazneen; Khaled Ksaibati. Variables impacting the severity of crashes involving traffic barriers on horizontal curves: actual crash analysis of interstate roads in Wyoming. International Journal of Crashworthiness 2020, 1 -11.

AMA Style

Amirarsalan Mehrara Molan, Sahima Nazneen, Khaled Ksaibati. Variables impacting the severity of crashes involving traffic barriers on horizontal curves: actual crash analysis of interstate roads in Wyoming. International Journal of Crashworthiness. 2020; ():1-11.

Chicago/Turabian Style

Amirarsalan Mehrara Molan; Sahima Nazneen; Khaled Ksaibati. 2020. "Variables impacting the severity of crashes involving traffic barriers on horizontal curves: actual crash analysis of interstate roads in Wyoming." International Journal of Crashworthiness , no. : 1-11.

Journal article
Published: 13 June 2020 in Accident Analysis & Prevention
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Past roadside safety studies mostly evaluated the impact of traffic barrier geometric features using simulation tools or by conducting field crash tests. While past simulation and field crash tests could present important findings for upgrading the geometric design of traffic barriers, there is still a gap regarding conducting an actual data analysis on side traffic barriers crashes with regards to their geometric dimensions. This paper aims at filling this gap by combining a statewide dataset of side traffic barrier geometric features with historical crashes on interstate roads in Wyoming. Therefore, geometric features including system height, post-spacing, lateral offset (from the edge of pavement), and side-slope of over 150 miles of side traffic barriers were inventoried by conducting a field survey on interstate roads in Wyoming. For the statistical analysis, a random-parameters ordered logit model was utilized to investigate variables impacting crash severity of side traffic barriers. It was found that system height could significantly impact the crash severity of side box beam barriers. Box beam barriers with a system height between 25 and 31 in. were identified to be less severe in comparison to other height categories, while showing minimum risks of severe crashes in the system height of 29−31 in.. On the other hand, box beam barriers with a height taller than 31 in. may increase crash severity.

ACS Style

Amirarsalan Mehrara Molan; Milhan Moomen; Khaled Ksaibati. Estimating the effect of geometric features of side traffic barriers on crash severity of interstate roads in Wyoming. Accident Analysis & Prevention 2020, 144, 105639 .

AMA Style

Amirarsalan Mehrara Molan, Milhan Moomen, Khaled Ksaibati. Estimating the effect of geometric features of side traffic barriers on crash severity of interstate roads in Wyoming. Accident Analysis & Prevention. 2020; 144 ():105639.

Chicago/Turabian Style

Amirarsalan Mehrara Molan; Milhan Moomen; Khaled Ksaibati. 2020. "Estimating the effect of geometric features of side traffic barriers on crash severity of interstate roads in Wyoming." Accident Analysis & Prevention 144, no. : 105639.

Report
Published: 01 April 2020 in Evaluation of Coordinated Ramp Metering (CRM) Implemented By Caltrans
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Coordinated ramp metering (CRM) is a critical component of smart freeway corridors that rely on real-time traffic data from ramps and freeway mainline to improve decision-making by the motorists and Traffic Management Center (TMC) personnel. CRM uses an algorithm that considers real-time traffic volumes on freeway mainline and ramps and then adjusts the metering rates on the ramps accordingly for optimal flow along the entire corridor. Improving capacity through smart corridors is less costly and easier to deploy than freeway widening due to high costs associated with right-of-way acquisition and construction. Nevertheless, conversion to smart corridors still represents a sizable investment for public agencies. However, in the U.S. there have been limited evaluations of smart corridors in general, and CRM in particular, based on real operational data. This project examined the recent Smart Corridor implementation on Interstate 80 (I-80) in the Bay Area and State Route 99 (SR-99, SR99) in Sacramento based on travel time reliability measures, efficiency measures, and before-and-after safety evaluation using the Empirical Bayes (EB) approach. As such, this evaluation represents the most complete before-and-after evaluation of such systems. The reliability measures include buffer index, planning time, and measures from the literature that account for both the skew and width of the travel time distribution. For efficiency, the study estimates the ratio of vehicle miles traveled vs. vehicle hour traveled. The research contextualizes before-and-after comparisons for efficiency and reliability measures through similar measures from another corridor (i.e., the control corridor of I-280 in District 4 and I-5 in District 3) from the same region, which did not have CRM implemented. The results show there has been an improvement in freeway operation based on efficiency data. Post-CRM implementation, travel time reliability measures do not show a similar improvement. The report also provides a counterfactual estimate of expected crashes in the post-implementation period, which can be compared with the actual number of crashes in the “after” period to evaluate effectiveness.

ACS Style

Amir Amir Molan, California Polytechnic State University, San Luis Obispo; Nivedha Nivedha Murugesan, San Jose State University; Alireza Alireza Shams, California Polytechnic State University, San Luis Obispo; Cristina Cristina Tortora, San Jose State University; Ghd Faridur Rahman; RailPros Jacky Loh; Anurag Anurag Pande, California Polytechnic State University, San Luis Obispo. Evaluation of Coordinated Ramp Metering (CRM) Implemented By Caltrans. Evaluation of Coordinated Ramp Metering (CRM) Implemented By Caltrans 2020, 1 .

AMA Style

Amir Amir Molan, California Polytechnic State University, San Luis Obispo, Nivedha Nivedha Murugesan, San Jose State University, Alireza Alireza Shams, California Polytechnic State University, San Luis Obispo, Cristina Cristina Tortora, San Jose State University, Ghd Faridur Rahman, RailPros Jacky Loh, Anurag Anurag Pande, California Polytechnic State University, San Luis Obispo. Evaluation of Coordinated Ramp Metering (CRM) Implemented By Caltrans. Evaluation of Coordinated Ramp Metering (CRM) Implemented By Caltrans. 2020; ():1.

Chicago/Turabian Style

Amir Amir Molan, California Polytechnic State University, San Luis Obispo; Nivedha Nivedha Murugesan, San Jose State University; Alireza Alireza Shams, California Polytechnic State University, San Luis Obispo; Cristina Cristina Tortora, San Jose State University; Ghd Faridur Rahman; RailPros Jacky Loh; Anurag Anurag Pande, California Polytechnic State University, San Luis Obispo. 2020. "Evaluation of Coordinated Ramp Metering (CRM) Implemented By Caltrans." Evaluation of Coordinated Ramp Metering (CRM) Implemented By Caltrans , no. : 1.

Articles
Published: 18 March 2020 in International Journal of Modelling and Simulation
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This paper proposes a new design called a partial cloverleaf progressA (parclo progressA) which could be considered as a substitute for failing conventional parclo A interchanges. Over 200 VISSIM simulation tests were conducted to make a comparison between the new parclo progressA and the conventional parclo A in terms of traffic operation. Also, the same tests were conducted in the Surrogate Safety Assessment Model to evaluate the safety performance of the designs. According to the results, the parclo progressA performed better than the conventional parclo A in terms of both traffic operation and traffic safety. The mean travel time in the parclo progressA with 2-phase signlas was significantly lower than the parclo A, especially when there are high turning traffic demands. Regarding the safety performance, the parclo progressA had about 25% fewer simulated conflict interactions compared to the parclo A with dual left turn lanes from the off-ramps.

ACS Style

Amirarsalan Mehrara Molan; Joseph E. Hummer. Proposing the new parclo progressA design as a substitute for the conventional partial cloverleaf A interchanges. International Journal of Modelling and Simulation 2020, 41, 284 -298.

AMA Style

Amirarsalan Mehrara Molan, Joseph E. Hummer. Proposing the new parclo progressA design as a substitute for the conventional partial cloverleaf A interchanges. International Journal of Modelling and Simulation. 2020; 41 (4):284-298.

Chicago/Turabian Style

Amirarsalan Mehrara Molan; Joseph E. Hummer. 2020. "Proposing the new parclo progressA design as a substitute for the conventional partial cloverleaf A interchanges." International Journal of Modelling and Simulation 41, no. 4: 284-298.

Articles
Published: 04 February 2020 in International Journal of Crashworthiness
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This paper seeks to identify variables affecting the severity of crashes involving traffic barrier end treatments. A field inventory was conducted to collect type, system height (from the ground to the top), lateral offset (from the edge of pavement), and side-slope of over 11,000 end treatments in the state of Wyoming. Then, the data collected was combined with historical end treatment crashes using the Critical Analysis Reporting Environment (CARE) software. Finally, a severity model was developed for end treatment crashes, considering a random-parameters ordered logit model. Among the end treatment types considered in this study, the end anchorage type A-FLEAT 350 was least likely to result in severe injuries in crashes. On the other hand, turned-down end terminal and the end anchorage WY-BET were involved with higher injury severity in crashes. End treatments located on a flat roadside were found to be less severe, showing a parameter estimate equal to –1.10 in the crash severity model. End treatment crashes involving pickup also had a lower probability of causing a severe injury crash compared to the other vehicle types.

ACS Style

Amirarsalan Mehrara Molan; Khaled Ksaibati. Factors impacting injury severity of crashes involving traffic barrier end treatments. International Journal of Crashworthiness 2020, 26, 202 -210.

AMA Style

Amirarsalan Mehrara Molan, Khaled Ksaibati. Factors impacting injury severity of crashes involving traffic barrier end treatments. International Journal of Crashworthiness. 2020; 26 (2):202-210.

Chicago/Turabian Style

Amirarsalan Mehrara Molan; Khaled Ksaibati. 2020. "Factors impacting injury severity of crashes involving traffic barrier end treatments." International Journal of Crashworthiness 26, no. 2: 202-210.

Journal article
Published: 01 December 2019 in Journal of Safety Research
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Despite the numerous safety studies done on traffic barriers' performance assessment, the effect of variables such as traffic barrier's height has not been identified considering a comprehensive actual crash data analysis. This study seeks to identify the impact of geometric variables (i.e., height, post-spacing, sideslope ratio, and lateral offset) on median traffic barriers' performance in crashes on interstate roads. Geometric dimensions of over 110 miles median traffic barriers on interstate Wyoming roads were inventoried in a field survey between 2016 and 2018. Then, the traffic barrier data collected was combined with historical crash records, traffic volume data, road geometric characteristics, and weather condition data to provide a comprehensive dataset for the analysis. Finally, an ordered logit model with random-parameters was developed for the severity of traffic barrier crashes. Based on the results, traffic barrier's height was found to impact crash severity. Crashes involving cable barriers with a height between 30″ and 42″ were less severe than other traffic barrier types, while concrete barriers with a height shorter than 32″ were more likely involved with severe injury crashes. As another important finding, the post-spacing of 6.1-6.3 ft. was identified as the least severe range in W-beam barriers. The results show that using flare barriers should reduce the number of crashes compared to parallel barriers.

ACS Style

Amirarsalan Mehrara Molan; Milhan Moomen; Khaled Ksaibati. Investigating the effect of geometric dimensions of median traffic barriers on crashes: Crash analysis of interstate roads in Wyoming using actual crash datasets. Journal of Safety Research 2019, 71, 163 -171.

AMA Style

Amirarsalan Mehrara Molan, Milhan Moomen, Khaled Ksaibati. Investigating the effect of geometric dimensions of median traffic barriers on crashes: Crash analysis of interstate roads in Wyoming using actual crash datasets. Journal of Safety Research. 2019; 71 ():163-171.

Chicago/Turabian Style

Amirarsalan Mehrara Molan; Milhan Moomen; Khaled Ksaibati. 2019. "Investigating the effect of geometric dimensions of median traffic barriers on crashes: Crash analysis of interstate roads in Wyoming using actual crash datasets." Journal of Safety Research 71, no. : 163-171.

Journal article
Published: 16 October 2019 in Journal of Traffic and Transportation Engineering (English Edition)
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Roadside safety is one of the important components of highway systems due to its considerable rate of high-severity crashes. Traffic barriers play a key role in reducing the crash severity and saving more lives on roadsides but choosing an inappropriate traffic barrier could decrease traffic barriers’ efficiency. This paper investigated the variables affecting crash severity in different traffic barrier types (cable, guardrail, and rigid) and vehicle types (truck, and non-truck). For this purpose, an ordinal logistic regression approach was conducted on the crash data collected between 2007 and 2016 in Wyoming. According to the results, different traffic barrier types show different relationships to crash severity based on posted speed limit at the site. In guardrail segments, a high-severity crash is more likely when the posted speed limit is more than 55 mph; however, cable barrier crashes were less severe in high-speed limit (>55 mph) areas. While light vehicles were more vulnerable to crashes hitting rigid barriers, no significant difference was found between performances of cable and rigid barriers in terms of truck crash severity. The analytical models proposed in this study would make a clear view for designers and decision-makers in selecting the most appropriate traffic barrier. Also, the effective factors introduced in each model could be used to rank the risk posed by existing traffic barrier segments based on traffic barrier type, truck volume percentage, and other highway characteristics.

ACS Style

Amirarsalan Mehrara Molan; Mahdi Rezapour; Khaled Ksaibati. Investigating the relationship between crash severity, traffic barrier type, and vehicle type in crashes involving traffic barrier. Journal of Traffic and Transportation Engineering (English Edition) 2019, 7, 125 -136.

AMA Style

Amirarsalan Mehrara Molan, Mahdi Rezapour, Khaled Ksaibati. Investigating the relationship between crash severity, traffic barrier type, and vehicle type in crashes involving traffic barrier. Journal of Traffic and Transportation Engineering (English Edition). 2019; 7 (1):125-136.

Chicago/Turabian Style

Amirarsalan Mehrara Molan; Mahdi Rezapour; Khaled Ksaibati. 2019. "Investigating the relationship between crash severity, traffic barrier type, and vehicle type in crashes involving traffic barrier." Journal of Traffic and Transportation Engineering (English Edition) 7, no. 1: 125-136.

Journal article
Published: 31 May 2019 in The Open Transportation Journal
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Background: Run Off The Road (ROTR) crashes are some of the most severe crashes that could occur on roadways. The main countermeasure that can be taken to address this type of crashe is traffic barrier installation. Although ROTR crashes can be mitigated significantly by traffic barriers, still traffic barrier crashes resulted in considerable amount of severe crashes. Besides, the types of traffic barriers, driver actions and performance play an important role in the severity of these crashes. Methods: This study was conducted by incorporating only traffic barrier crashes in Wyoming. Based on the literature review there are unique contributory factors in different crash types. Therefore, in addition to focusing on traffic barrier crashes, crashes were divided into two different highway classes: interstate and non-interstate highways. Results: The result of proportional odds assumption was an indication that multinomial logistic regression model is appropriate for both non-interstate and interstates crashes involved with traffic barriers. The results indicated that road surface conditions, age, driver restraint and negotiating a curve were some of the factors that impact the severity of traffic barrier crashes on non-interstate highways. On the other hand, the results of interstate barrier crashes indicated that besides types of barriers, driver condition, citation record, speed limit compliance were some of the factors that impacted the interstate traffic barrier crash severity. Conclusion: The results of this study would provide the policymakers with the directions to take appropriate countermeasures to alleviate the severity of traffic barrier crashes.

ACS Style

Mahdi Rezapour; Amirarsalan Mehrara Molan; Khaled Ksaibati. Application of Multinomial Regression Model to Identify Parameters Impacting Traffic Barrier Crash Severity. The Open Transportation Journal 2019, 13, 57 -64.

AMA Style

Mahdi Rezapour, Amirarsalan Mehrara Molan, Khaled Ksaibati. Application of Multinomial Regression Model to Identify Parameters Impacting Traffic Barrier Crash Severity. The Open Transportation Journal. 2019; 13 (1):57-64.

Chicago/Turabian Style

Mahdi Rezapour; Amirarsalan Mehrara Molan; Khaled Ksaibati. 2019. "Application of Multinomial Regression Model to Identify Parameters Impacting Traffic Barrier Crash Severity." The Open Transportation Journal 13, no. 1: 57-64.

Article
Published: 10 April 2019 in Journal of Modern Transportation
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Traffic barriers are in widespread all around the USA as safety countermeasures for reducing the severity of run-off-road crashes. The effect of traffic barriers’ dimension had been ignored in past real-world crash studies due to the considerable cost and time needed for collecting field data. This paper presented two new analytical models to investigate the effect of different variables on the severity of crashes involving traffic barriers, and end treatments. For this reason, a field survey was conducted on over 1.3 million linear feet of traffic barriers (approximately 4,176 miles road) in Wyoming to measure traffic barriers’ geometric features like height, length, offset, and slope rate. The collected data included 55% of all non-interstate roads of Wyoming. Based on results, the crashes involving box beam barriers were less severe than the crashes involved with W-beam or concrete barriers. The traffic barriers with a height between 28 and 31 in. were found safer than the traffic barriers shorter than 28 in., while there was no significant difference between the traffic barriers taller than 31 in. to those shorter than 28 in. in terms of crash severity. The end treatments located nearer to the traffic lane had lower crash severity.

ACS Style

Amirarsalan Mehrara Molan; Mahdi Rezapour; Khaled Ksaibati. Modeling traffic barriers crash severity by considering the effect of traffic barrier dimensions. Journal of Modern Transportation 2019, 27, 141 -151.

AMA Style

Amirarsalan Mehrara Molan, Mahdi Rezapour, Khaled Ksaibati. Modeling traffic barriers crash severity by considering the effect of traffic barrier dimensions. Journal of Modern Transportation. 2019; 27 (2):141-151.

Chicago/Turabian Style

Amirarsalan Mehrara Molan; Mahdi Rezapour; Khaled Ksaibati. 2019. "Modeling traffic barriers crash severity by considering the effect of traffic barrier dimensions." Journal of Modern Transportation 27, no. 2: 141-151.

Journal article
Published: 21 March 2019 in Accident Analysis & Prevention
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Most existing interchanges in the United States were built more than 50 years ago based on old design policies. Many of these designs are not consistent with current traffic and pedestrian demands anymore. Therefore, this inconsistency has caused problems regarding operation and safety. This paper models safety performance of a new design called super diverging diamond interchange (super DDI) considering VISSIM simulation and surrogate safety assessment model (SSAM). Six other interchange designs were also considered for comparing to the new super DDI design. Overall, 252 simulation scenarios were modeled in VISSIM and then tested by SSAM. Also, the same number of tests were considered to evaluate pedestrian performance of the designs considered in this study. Based on results, super DDI showed a high potential either in terms of traffic safety and pedestrian safety. In comparison to other designs, super DDI had the minimum number of simulated conflicts as well as the lowest mean speed and time to collision (TTC) of simulated conflicts. This fact shows that super DDI could perform promising in reducing crash frequency and crash severity. Reviewing the geometry of the super DDI, lower traffic involving in each conflict point should be one of the main reasons for the promising traffic safety performance of the design. Regarding pedestrian performance, super DDI got the third rank of the lowest mean pedestrian travel times. There is no free-flowing conflict between vehicles and pedestrians in a super DDI. Therefore, pedestrian paths of the super DDI are predicted to be safer than the paths in a typical DDI design.

ACS Style

Amirarsalan Mehrara Molan; Joseph E. Hummer; Khaled Ksaibati. Modeling safety performance of the new super DDI design in terms of vehicular traffic and pedestrian. Accident Analysis & Prevention 2019, 127, 198 -209.

AMA Style

Amirarsalan Mehrara Molan, Joseph E. Hummer, Khaled Ksaibati. Modeling safety performance of the new super DDI design in terms of vehicular traffic and pedestrian. Accident Analysis & Prevention. 2019; 127 ():198-209.

Chicago/Turabian Style

Amirarsalan Mehrara Molan; Joseph E. Hummer; Khaled Ksaibati. 2019. "Modeling safety performance of the new super DDI design in terms of vehicular traffic and pedestrian." Accident Analysis & Prevention 127, no. : 198-209.

Journal article
Published: 05 March 2019 in Transportation Research Record: Journal of the Transportation Research Board
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Subscription and open access journals from SAGE Publishing, the world's leading independent academic publisher.

ACS Style

Amirarsalan Mehrara Molan; Joseph E. Hummer; Khaled Ksaibati. Introducing the Super DDI as a Promising Alternative Service Interchange. Transportation Research Record: Journal of the Transportation Research Board 2019, 2673, 586 -597.

AMA Style

Amirarsalan Mehrara Molan, Joseph E. Hummer, Khaled Ksaibati. Introducing the Super DDI as a Promising Alternative Service Interchange. Transportation Research Record: Journal of the Transportation Research Board. 2019; 2673 (3):586-597.

Chicago/Turabian Style

Amirarsalan Mehrara Molan; Joseph E. Hummer; Khaled Ksaibati. 2019. "Introducing the Super DDI as a Promising Alternative Service Interchange." Transportation Research Record: Journal of the Transportation Research Board 2673, no. 3: 586-597.

Journal article
Published: 19 January 2019 in Journal of Transportation Safety & Security
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ACS Style

Amirarsalan Mehrara Molan; Mahdi Rezapour; Khaled Ksaibati. Modeling the impact of various variables on severity of crashes involving traffic barriers. Journal of Transportation Safety & Security 2019, 12, 800 -817.

AMA Style

Amirarsalan Mehrara Molan, Mahdi Rezapour, Khaled Ksaibati. Modeling the impact of various variables on severity of crashes involving traffic barriers. Journal of Transportation Safety & Security. 2019; 12 (6):800-817.

Chicago/Turabian Style

Amirarsalan Mehrara Molan; Mahdi Rezapour; Khaled Ksaibati. 2019. "Modeling the impact of various variables on severity of crashes involving traffic barriers." Journal of Transportation Safety & Security 12, no. 6: 800-817.

Journal article
Published: 07 January 2019 in SAE International Journal of Commercial Vehicles
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The study of road loads on trucks plays a major role in assessing the effect of heavy-vehicle design on fuel conservation measures. Coastdown testing with full-scale vehicles in the field offers a good avenue to extract drag components, provided that random instrumentation faults and biase

ACS Style

Milhan Moomen; Mahdi Rezapour; Amirarsalan Mehrara Molan; Khaled Ksaibati. Assessing Road Load Coefficients of a Semi-Trailer Combination Using a Mechanical Simulation Software with Calibration Corrections. SAE International Journal of Commercial Vehicles 2019, 12, 31 -44.

AMA Style

Milhan Moomen, Mahdi Rezapour, Amirarsalan Mehrara Molan, Khaled Ksaibati. Assessing Road Load Coefficients of a Semi-Trailer Combination Using a Mechanical Simulation Software with Calibration Corrections. SAE International Journal of Commercial Vehicles. 2019; 12 (1):31-44.

Chicago/Turabian Style

Milhan Moomen; Mahdi Rezapour; Amirarsalan Mehrara Molan; Khaled Ksaibati. 2019. "Assessing Road Load Coefficients of a Semi-Trailer Combination Using a Mechanical Simulation Software with Calibration Corrections." SAE International Journal of Commercial Vehicles 12, no. 1: 31-44.

Research article
Published: 17 June 2018 in Transportation Research Record: Journal of the Transportation Research Board
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Most U.S. highway agencies recognize the importance of designing safe, short, and comfortable paths for pedestrians. Providing such an acceptable condition for pedestrians requires specific attention at intersections and service interchanges due to their interaction with other modes of transportation. The main objective of this research was to analyze pedestrian operation at two new service interchanges—the synchronized and Milwaukee B interchanges—in comparison with four existing designs. The analysis consists of three main parts: (1) a general comparison among the designs for pedestrian performances in terms of safety, travel time, and the level of service; (2) investigation of the effects of vehicles on pedestrian performance; and (3) modeling the impact of pedestrians on the traffic operation of vehicles. A comprehensive series of simulation tests were run using VISSIM and Synchro to study the pedestrian performance of interchanges in various situations of traffic volume, turning traffic ratio, traffic distribution, and percentage of heavy vehicles. The results indicated that a relatively safe condition is expected for pedestrians in the proposed new designs in comparison with the existing interchanges; however, the pedestrians’ travel time was lower in all the existing designs than in the new designs except the diverging diamond interchange (DDI). The DDI, one of the most popular alternative interchanges, showed the worst performance in all the aspects of the pedestrian analysis. Despite the very good performance of conventional diamond interchange regarding pedestrian travel time and safety, pedestrians could have a significant negative impact on vehicle travel time through a diamond.

ACS Style

Amirarsalan Mehrara Molan; Joseph E. Hummer. Simulation Modeling of Pedestrian Performance in the New Synchronized and Milwaukee B Interchanges versus Existing Designs. Transportation Research Record: Journal of the Transportation Research Board 2018, 2672, 151 -160.

AMA Style

Amirarsalan Mehrara Molan, Joseph E. Hummer. Simulation Modeling of Pedestrian Performance in the New Synchronized and Milwaukee B Interchanges versus Existing Designs. Transportation Research Record: Journal of the Transportation Research Board. 2018; 2672 (35):151-160.

Chicago/Turabian Style

Amirarsalan Mehrara Molan; Joseph E. Hummer. 2018. "Simulation Modeling of Pedestrian Performance in the New Synchronized and Milwaukee B Interchanges versus Existing Designs." Transportation Research Record: Journal of the Transportation Research Board 2672, no. 35: 151-160.

Journal article
Published: 31 May 2018 in The Open Transportation Journal
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Based on the statistics, roadsides include a considerable portion of the fatal crashes annually. Barrier systems are one of the important components of roadside that plays a key role in mitigating the severity of these crashes and save more lives. Despite the substantial role of barrier systems, unfortunately, there is no unified rating system in the barrier condition assessments to utilize for the optimization of the improvements. As the primary contribution in this study, a new Barrier Condition Index (BCI) was proposed to unify the barrier assessment studies to use the same reference for rating barrier systems. This fact makes the decision-makers able to establish a prioritized ranking for optimizing the barrier improvements. For this purpose, the research investigated a comprehensive list of damages in barrier systems. Then, appropriate coefficients were given to the damage types based on their effects on the performance of the system reviewing the previous works. To show the practicability of the new BCI as an example for the whole procedure of the assessment, six different barrier systems located in Wind River Indian Reservation (WRIR), Wyoming, were also evaluated in the study. Based on the evaluation done, the BCI was used to rank the performance of the barriers. Three of the barrier segments at WRIR was introduced as the high-severity level which should be considered in the first priority of the improvement phase.

ACS Style

Amirarsalan Mehrara Molan; Khaled Ksaibati. Developing the New Barrier Condition Index (BCI) to Unify the Barrier Assessments - A Case Study in Wind River Indian Reservation, Wyoming. The Open Transportation Journal 2018, 12, 182 -191.

AMA Style

Amirarsalan Mehrara Molan, Khaled Ksaibati. Developing the New Barrier Condition Index (BCI) to Unify the Barrier Assessments - A Case Study in Wind River Indian Reservation, Wyoming. The Open Transportation Journal. 2018; 12 (1):182-191.

Chicago/Turabian Style

Amirarsalan Mehrara Molan; Khaled Ksaibati. 2018. "Developing the New Barrier Condition Index (BCI) to Unify the Barrier Assessments - A Case Study in Wind River Indian Reservation, Wyoming." The Open Transportation Journal 12, no. 1: 182-191.

Journal article
Published: 01 February 2018 in Journal of Transportation Engineering, Part A: Systems
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This research evaluated the traffic performance of two new service interchange designs—the synchronized design which is related to a superstreet intersection and the Milwaukee B design that is related to a parclo B design—as possible substitutes where existing interchanges are failing. The travel time of vehicles was selected as the criteria for operation evaluation. Over 1,000 simulation scenarios modeled the traffic operation of six different interchanges (two new and four existing interchanges) in different conditions of traffic volume, traffic distribution, left/right turning volume ratios, and heavy vehicle percentage. As simulation validation, real travel times at three interchanges were collected using probe vehicle data that compared fairly well to simulation outputs. A two-way analysis of variance (ANOVA) was conducted to examine the differences in mean values of travel time between the interchanges and to investigate the variables that affected the travel time of each design. Overall, the Milwaukee B showed the best performance among all the interchanges. The synchronized interchange looks promising as a substitute for a diamond interchange with dominant through traffic. The synchronized and diverging diamond interchanges showed almost the same results while handling moderate levels of turning volume.

ACS Style

Amirarsalan Mehrara Molan; Joseph E. Hummer. Travel Time Evaluation of Synchronized and Milwaukee B as New Interchange Designs. Journal of Transportation Engineering, Part A: Systems 2018, 144, 04017074 .

AMA Style

Amirarsalan Mehrara Molan, Joseph E. Hummer. Travel Time Evaluation of Synchronized and Milwaukee B as New Interchange Designs. Journal of Transportation Engineering, Part A: Systems. 2018; 144 (2):04017074.

Chicago/Turabian Style

Amirarsalan Mehrara Molan; Joseph E. Hummer. 2018. "Travel Time Evaluation of Synchronized and Milwaukee B as New Interchange Designs." Journal of Transportation Engineering, Part A: Systems 144, no. 2: 04017074.

Journal article
Published: 01 December 2017 in Accident Analysis & Prevention
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Interchanges have high crash rates and large impacts on traffic operations. The main objective of this research is to analyze the safety performance of two new interchanges, the synchronized interchange and the Milwaukee B interchange. The primary method of study was microscopic simulation modeling using the Surrogate Safety Assessment Model (SSAM) program to estimate the quantity and type of conflicting interactions in each interchange. A comprehensive series of simulation scenarios were considered to include different conditions of traffic volumes, traffic turning ratios, traffic distribution, and heavy vehicles percentages. Afterward, outcomes were analyzed with two-way Analyses of Variance (ANOVAs) to compare the mean values of conflicts. Based on the results, the diverging diamond interchange (DDI) and Milwaukee B were the safest designs regarding observed conflicting interactions in the simulation models; however, the DDI did not seem as reliable from the viewpoint of wrong way movements. The new synchronized interchange, the parclo B, and the Milwaukee A (an existing interchange in Milwaukee, WI) showed the same rate of conflicts. The synchronized interchange may be advantageous because it was estimated to reduce the severity of crashes due to fewer crossing conflicts, a lower speed of conflicts, and a higher time to collision. The conventional diamond was the most dangerous design based on our measures. The DDI and the synchronized interchange look like plausible substitutes for reconstructing an unsafe diamond interchange due to the similarities in their required space.

ACS Style

Amirarsalan Mehrara Molan; Joseph E. Hummer. Safety analysis of the new synchronized and milwaukee B interchanges in comparison to existing designs. Accident Analysis & Prevention 2017, 109, 29 -35.

AMA Style

Amirarsalan Mehrara Molan, Joseph E. Hummer. Safety analysis of the new synchronized and milwaukee B interchanges in comparison to existing designs. Accident Analysis & Prevention. 2017; 109 ():29-35.

Chicago/Turabian Style

Amirarsalan Mehrara Molan; Joseph E. Hummer. 2017. "Safety analysis of the new synchronized and milwaukee B interchanges in comparison to existing designs." Accident Analysis & Prevention 109, no. : 29-35.