Master of Science

thesisOne of the major challenges for Traffic Operations Center (TOC) operators is to determine the nature of their response to traffic incidents. This applies to both operators' training and real traffic management. While incidents vary by location and degree of disruption, operators' responses vary by how quickly they are implemented and what degree of actions they take. Operators can react instantaneously and divert traffic from an entire highway, or simply wait and apply a mild variable message. Travelers' delay under incident conditions depends not only on incident severity, but also on the effectiveness of response to an incident. This is an analysis of a wide range of incidents and responses for the set of critical locations on a test Salt Lake Valley freeway network. It uses VISSIM microsimulation to determine optimal responses under various incident conditions. Incident severity is represented through Incident Location, Incident Duration and Lane Closure. Incident response is defined through the Response Time, and Variable Message Sign (VMS) Levels and VMS Display Time. As expected, the resulting degree of incident disruption is mitigated by the speed of response and the proportion of drivers who divert. However, for certain minor incidents, a VMS induced traffic diversion might increase travelers' delay instead of reducing it

Doctor of Philosophy

dissertationThe interest in multimodal transportation improvements is increasing in cities across the U.S. Investing in multimodal infrastructure benefits the portion of urban population that is unable to drive due to a variety of reasons such as personal preference, age, and affordability. It is also well known that active transportation such as walking, biking, and taking transit, can improve public health due to increased physical activity, and reduce traffic congestion by reducing the average person's delay. While improved multimodal infrastructure and accessibility attracts new users, it can possibly increase their exposure to risk from crashes. In urban areas where the "safety in numbers phenomenon" does not exist, nonmotorized user vulnerability becomes a predominant risk factor when they are involved in a crash, even at lower vehicle speeds. This dissertation aims to explore the factors that are associated with safety outcomes in urban multimodal transportation systems, and develop methods that can be used to estimate safety effects of multimodal infrastructure and accessibility improvements. Using Chicago as a case study, a comprehensive dataset is developed that significantly contributes to the existing literature by including socio-economic, land use, road network, travel demand, and crash data. Area-wide analysis on the census tract level provides a broader perspective about safety issues that multimodal users encounter in cities. The characteristics of a multimodal transportation system are expressed through the presence of multimodal infrastructure, street connectivity and network completeness, and accessibility to destinations for multimodal users. A set of statistical areal safety models (SASM) based on both frequentist and Bayesian statistical inference is applied to estimate the factors that are associated with total and severe vehicular, pedestrian, and bicyclist crashes in urban multimodal transportation systems. The results show that the current safety evaluation methods need to acknowledge the complexity of multimodal transportation systems through the inclusion of diverse factors that may influence safety outcomes, particularly for more vulnerable users. The methods developed in this research can further be used to expand the current practice of evaluating multimodal transportation safety, and planning for city-wide investments in multimodal infrastructure and improved accessibility, while being able to estimate the expected safety outcomes

Safety analysis of freeway on-ramp merging with the presence of autonomous vehicles

Freeway on-ramp merging areas are high-risk areas for motor vehicle crashes and conflicts due to the variety of driving styles, the difference in mainline and ramp traffic states, and factors related to roadway design and traffic control. The emerging Autonomous Vehicle (AV) technologies are expected to bring substantial improvements in ramp merging operations in general, including the possibility to reduce traffic conflicts and crashes by partially or fully eliminating the critical factors related to the human drivers. In order to investigate the potential safety impacts of AVs at on-ramp merging, this study first proposes a novel conflict index in theory as a specific indicator for ramp merging safety. Then, a merging conflict model is introduced to estimate the index value in various cases by considering the interactions between the mainline and ramp vehicles. In order to account for real-world uncertainties and variations in various crash-contributing factors, the proposed approach incorporates Monte-Carlo method and probabilistic distributions calibrated on the empirical freeway data. The developed approach is later applied in a case study with incremental AV market penetration rates to investigate AV safety impacts at on-ramp merging. The results show clear benefits of AVs in reducing the frequency and severity of the critical merging events. In addition, a sensitivity analysis on essential model parameters shows that the merging safety of AVs is closely related to their gap acceptance policy and the proper functioning of the driving systems, providing further insights into the future development of AVs

Fractional flow reserve of intermediate lesions on collateral donor coronary arteries after myocardial infarction

Fractional flow reserve (FFR) is the gold standard for the functional assessment of coronary arteries. The aim of this study was to evaluate the relation between angiography, QCA and FFR in borderline lesions on collateral donor coronary arteries. In addition, FFR is compared with the angiographic appearance of collaterals to infarction-related arteries and echocardiographically assessed viability of infarct related the LV wall. In 60 patients with previous IM and occluded IRA, functional assessment of borderline coronary stenosis (30-70% DS) on collaterals donor artery was performed. We have not found statistically significant differences in these parameters between groups with different angiographic appearances of collaterals and different viability of distal myocardium. However, we found higher FFR values in diabetic patients (p=0.018). Higher FFR values in diabetic patients reveal the negative effects of diabetes on collateral growth and myocardial viability

Hemijski sastav M. Semimembranosus i M. Longissimus Thoracis et Lumborum svinja pet čistih rasa odgajanih u Vojvodini

U ovom radu utvrđen je sadržaj vlage, proteina, ukupne masti i ukupnog pepela u M. semimembranosus (SM) i M. longissimus thoracis et lumborum (LTL) pet čistih rasa svinja: Velika Bela (n=118), Landras (n=116), Durok (n=112), Hempšir (n=112) i Pietren (n=121), odgajanih u Vojvodini. Osnovni hemijski sastav određen je ISO metodama. Ukupno, prosečan sadržaj (g/100g) vlage, proteina, ukupne masti i ukupnog pepela u svim ispitanim mišićima SM i LTL (n=1158) je bio: 75.68, 21.73, 1.36 i 1.14, respektivno. Svinjsko meso proizvedeno u Vojvodini pokazuje sličan sadržaj vlage, proteina, masti i pepela u poređenju sa sadržajima utvrđenim u drugim zemljama

Hemijski sastav jetri i bubrega svinja pet čistih rasa odgajanih u Vojvodini

In this paper the content of moisture, protein, total fat and total ash in the M. semimembranosus (SM) and M. longissimus thoracis et lumborum (LTL) from five purebred pigs: Large White (n=118), Landrace (n=116), Duroc (n=112), Hampshire (n=112) and Pietrain (n=121), reared in Vojvodina was determined. Components of proximate composition were determined by ISO methods. Overall, the average content (g/100g) of moisture, protein, total fat and total ash in all the SM and LTL (n=1158) was: 75.68, 21.73, 1.36 and 1.14, respectively. The Vojvodian pork showed same moisture, protein, total fat and total ash content compared with the values found in other countries.U ovom radu utvrđen je sadržaj vlage, proteina, ukupne masti i ukupnog pepela u jetrama i bubrezima svinja pet čistih rasa: Velika Bela (n=118), Landras (n=116), Durok (n=112), Hempšir (n=112) i Pietren (n=121), odgajanih u Vojvodini. Osnovni hemijski sastav određen je ISO metodama. Rasa svinja ne utiče značajno (P>0.05), dok vrsta iznutrice utiče značajno (P<0.05; P<0.001) na sadržaj vlage, proteina, ukupne masti i ukupnog pepela. Prosečan sadržaj (g/100g) vlage, proteina, ukupne masti i ukupnog pepela u svim ispitanim jetrama (n=579) je bio: 71.05, 21.34, 3.24 i 1.48, dok je u svim ispitanim bubrezima (n=579) bio: 79.43, 16.16, 3.13 i 1.20, respektivno

Dairying, diseases and the evolution of lactase persistence in Europe

Update notice Author Correction: Dairying, diseases and the evolution of lactase persistence in Europe (Nature, (2022), 608, 7922, (336-345), 10.1038/s41586-022-05010-7) Nature, Volume 609, Issue 7927, Pages E9, 15 September 2022In European and many African, Middle Eastern and southern Asian populations, lactase persistence (LP) is the most strongly selected monogenic trait to have evolved over the past 10,000 years(1). Although the selection of LP and the consumption of prehistoric milk must be linked, considerable uncertainty remains concerning their spatiotemporal configuration and specific interactions(2,3). Here we provide detailed distributions of milk exploitation across Europe over the past 9,000 years using around 7,000 pottery fat residues from more than 550 archaeological sites. European milk use was widespread from the Neolithic period onwards but varied spatially and temporally in intensity. Notably, LP selection varying with levels of prehistoric milk exploitation is no better at explaining LP allele frequency trajectoriesthan uniform selection since the Neolithic period. In the UK Biobank(4,5) cohort of 500,000 contemporary Europeans, LP genotype was only weakly associated with milk consumption and did not show consistent associations with improved fitness or health indicators. This suggests that other reasons for the beneficial effects of LP should be considered for its rapid frequency increase. We propose that lactase non-persistent individuals consumed milk when it became available but, under conditions of famine and/or increased pathogen exposure, this was disadvantageous, driving LP selection in prehistoric Europe. Comparison of model likelihoods indicates that population fluctuations, settlement density and wild animal exploitation-proxies for these drivers-provide better explanations of LP selection than the extent of milk exploitation. These findings offer new perspectives on prehistoric milk exploitation and LP evolution.Peer reviewe

Flow-level coordination of connected and autonomous vehicles in multilane freeway ramp merging areas

On-ramp merging areas are deemed to be typical bottlenecks for freeway networks due to the intensive disturbances induced by the frequent merging, weaving, and lane-changing behaviors. The Connected and Autonomous Vehicles (CAVs), benefited from their capabilities of real-time communication and precise motion control, hold an opportunity to promote ramp merging opera- tion through enhanced cooperation. The existing CAV cooperation strategies are mainly designed for single-lane freeways, although multilane configurations are more prevailing in the real-world. In this paper, we present a flow-level CAV coordination strategy to facilitate merging operation in multilane freeways. The coordination integrates lane-change rules between mainstream lanes, proactive creation of large merging gaps, and platooning of ramp vehicles for enhanced benefits in traffic flow stability and efficiency. The strategy is formulated under an optimization framework, where the optimal control plan is determined based on real-time traffic conditions. The impacts of tunable model parameters on the produced control plan are discussed in detail. The efficiency of the proposed multilane strategy is demonstrated in a micro-simulation environment. The results show that the coordination can substantially improve the overall ramp merging efficiency and prevent recurrent traffic congestions, especially under high traffic volume conditions

Use of Spatiotemporal Constraints to Quantify Transit Accessibility Case Study of Potential Transit-Oriented Development in West Valley City, Utah

Accessibility emerges as the transportation performance measure that emphasizes the benefits to transportation system users and captures more than the speed of travel. Transit accessibility shows how easy it is for an individual to travel to a desired destination by using public transit. However, for transit to be considered as an option in mode choice at all, there has to be a feasible transit route leading from a given origin to a desirable destination within the available time frame. This study used spatial and temporal constraints and a set of transit features that affected access to transit to develop a conceptual framework for transit accessibility measurements in a potential transit-oriented development (TOD) location in West Valley City, Utah. As this network develops more transit-friendly features, temporal and spatial accessibility indicators will provide useful information on the opportunities that users can reach by using transit. The proposed methodology was based on traffic and transit data from the case study network and used an open source tool to perform transit accessibility measurements by calculating the number of accessible transit stops from each origin. The methodology considered network features, acceptable walking time, available time budget, transit schedule variability, and spatial constraints as impact factors in accessibility measurements. The goal of the study was to establish a feasible set of transit accessibility indicators that would be used for both the case study street network and transit service modifications to transform the network into a transit-friendly and eventually a TOD environment

Exploring the safety in numbers effect for vulnerable road users on a macroscopic scale

A “Safety in Numbers” effect for a certain group of road users is present if the number of crashes increases at a lower rate than the number of road users. The existence of this effect has been invoked to justify investments in multimodal transportation improvements in order to create more sustainable urban transportation systems by encouraging walking, biking, and transit ridership. The goal of this paper is to explore safety in numbers effect for cyclists and pedestrians in areas with different levels of access to multimodal infrastructure. Data from Chicago served to estimate the expected number of crashes on the census tract level by applying Generalized Additive Models (GAM) to capture spatial dependence in crash data. Measures of trip generation, multimodal infrastructure, network connectivity and completeness, and accessibility were used to model travel exposure in terms of activity, number of trips, trip length, travel opportunities, and conflicts. The results show that a safety in numbers effect exists on a macroscopic level for motor vehicles, pedestrians, and bicyclists