The study investigates the age of at-fault drivers as a contributing factor for fatal crashes in Florida. The main objective of the research was to provide an in-depth analysis of the relationships between the ages of the at-fault drivers and different aspects of roadway, traffic, weather, and other related contributing factors, and recommend various countermeasures, both behavioral and roadway-related so that appropriate actions can be initiated to improve safety on Florida's highways. It also investigates the relationships between age vs. race, and age vs. sex. The study focuses on the driving behaviors of the younger (=years) and older (65-74 years, and >=75 years) drivers although the data of middle-age (25-64 years) drivers are also analyzed.=75 years) drivers although the data of middle-age (25-64 years) drivers are also analyzed. The younger and older drivers of both sexes are more likely to cause fatal crashes compared to the 'average' drivers. Among these, the female oldest (>=75 years) drivers are at highest level of vulnerability of causing fatal crashes followed by younger male drivers. The younger drivers of all races and only the white older drivers are more likely to cause such crashes. The older drivers of black, Hispanic, and 'other' races are less likely to cause fatal crashes compared to the 'average' drivers. In case of number of vehicles involved in crashes, the younger drivers are more likely to contribute to 1-vehicle, 2-vehicle, 3-vehicle, and >=4-vehicle crashes while the older drivers are also more likely to cause all of these types, except 1-vehicle crashes.=75 years) drivers are at highest level of vulnerability of causing fatal crashes followed by younger male drivers. The younger drivers of all races and only the white older drivers are more likely to cause such crashes. The older drivers of black, Hispanic, and 'other' races are less likely to cause fatal crashes compared to the 'average' drivers. In case of number of vehicles involved in crashes, the younger drivers are more likely to contribute to 1-vehicle, 2-vehicle, 3-vehicle, and >=4-vehicle crashes while the older drivers are also more likely to cause all of these types, except 1-vehicle crashes.=4-vehicle crashes while the older drivers are also more likely to cause all of these types, except 1-vehicle crashes. The study finds significant impacts of age of the at-fault drivers on contributing factors like crash hour, lighting conditions, road grades, road surface types, site locations, and vehicle speed while no significant impacts are found on road surface conditions, weather conditions, lane types (left, right, etc.), and shoulder types. The study reveals that the older drivers are involved in more intersection crashes than non-intersection crashes while the situation is opposite for the younger drivers. Among others the reasons for intersection crashes by the older drivers include misjudgment of speeds of the oncoming vehicles (18.0%), failure to observe the vehicle/all sides before approaching the intersection (17.0%), disregarding traffic signals (13.4%), and improper left turn (12.4%) are four major contributing factors each of which contributes to >=10% of intersection crashes by the older drivers. In case of non-intersection crashes, the study reveals that sudden loss of control contributes to more than one-third (37.1%) while driving under the influence of alcohol contributes to almost one-fifth (18.6%) of such crashes.=10% of intersection crashes by the older drivers. In case of non-intersection crashes, the study reveals that sudden loss of control contributes to more than one-third (37.1%) while driving under the influence of alcohol contributes to almost one-fifth (18.6%) of such crashes. It is evident that driving under the influence of alcohol (28.4%), exceeding safe speed limits (19.7%), and loss of control (19.7%) by the younger drivers are three major causes of fatal crashes in Florida, specially the 1-vehicle, high-speed, pedestrian/bicycle related, and loss of control type crashes. Among others disregarding traffic signals (6.6%) and failure to stop to avoid rear-end collision (6.3%) contribute to >=5% while failure to observe vehicles/all sides (3.3%), disregarding stop signs (3.0%), improper left turn (2.3%), and improper lane change (2.0%) contribute to >=2% of crashes on highways by the younger drivers whether at intersection or non-intersection. In case of intersection crashes, driving under the influence of alcohol (23.9%), disregarding traffic signals (18.8%), and exceeding safe speed limits (12.3%) come out as three major contributing causes. Other important contributing factors are disregarding stop signs, failure to observe vehicles/all sides, failure to stop to avoid rear-end collision, improper left turn, and loss of control that contribute to >=5% of intersection crashes. On the other hand, driving under the influence of alcohol (30.7%), loss of control of the vehicle (27.6%), exceeding safe speed limits (23.7%), and failure to stop the vehicle to avoid rear-end collision (5.8%) come out as four major contributing factors that cause >=5% of the non-intersection crashes by these drivers.=5% while failure to observe vehicles/all sides (3.3%), disregarding stop signs (3.0%), improper left turn (2.3%), and improper lane change (2.0%) contribute to >=2% of crashes on highways by the younger drivers whether at intersection or non-intersection. In case of intersection crashes, driving under the influence of alcohol (23.9%), disregarding traffic signals (18.8%), and exceeding safe speed limits (12.3%) come out as three major contributing causes. Other important contributing factors are disregarding stop signs, failure to observe vehicles/all sides, failure to stop to avoid rear-end collision, improper left turn, and loss of control that contribute to >=5% of intersection crashes. On the other hand, driving under the influence of alcohol (30.7%), loss of control of the vehicle (27.6%), exceeding safe speed limits (23.7%), and failure to stop the vehicle to avoid rear-end collision (5.8%) come out as four major contributing factors that cause >=5% of the non-intersection crashes by these drivers.=2% of crashes on highways by the younger drivers whether at intersection or non-intersection. In case of intersection crashes, driving under the influence of alcohol (23.9%), disregarding traffic signals (18.8%), and exceeding safe speed limits (12.3%) come out as three major contributing causes. Other important contributing factors are disregarding stop signs, failure to observe vehicles/all sides, failure to stop to avoid rear-end collision, improper left turn, and loss of control that contribute to >=5% of intersection crashes. On the other hand, driving under the influence of alcohol (30.7%), loss of control of the vehicle (27.6%), exceeding safe speed limits (23.7%), and failure to stop the vehicle to avoid rear-end collision (5.8%) come out as four major contributing factors that cause >=5% of the non-intersection crashes by these drivers.=5% of intersection crashes. On the other hand, driving under the influence of alcohol (30.7%), loss of control of the vehicle (27.6%), exceeding safe speed limits (23.7%), and failure to stop the vehicle to avoid rear-end collision (5.8%) come out as four major contributing factors that cause >=5% of the non-intersection crashes by these drivers.=5% of the non-intersection crashes by these drivers. In brief, the study reveals that driving under the influence of alcohol is the sole important contributing factor for all types of crashes by both younger and older drivers, except the intersection crashes by the older drivers for which misjudgment of speed and failure to observe are the major contributing factors. Other important factors are exceeding safe speed limits, disregarding traffic signals, and sudden loss of control of the vehicles. Another important finding of the study is that the investigation officers have tendency to frequently use the terms 'careless driving' for the younger-non-intersection crashes and 'failure to yield right of way' for older-intersection crashes. Finally, the study finds that about half of the at-fault drivers do not wear safety equipments that cause severe fatality. The study recommends that more efficient and frequent public transit services should be provided to the older drivers, and their driving licenses should be renewed every year to lessen the number of older drivers on the streets. On the other hand, training and educational programs should be initiated for the younger drivers. Stricter laws should be introduced for driving under the influence of alcohol/drug, driving at unsafe speeds, not wearing seat belts, and other offences so the younger drivers act with more responsibility on the streets. The numbers of traffic and billboard signs should also be kept at the minimum so the older drivers are not confused with unnecessary signs. / A Thesis submitted to the Department of Civil & Environmental Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Degree Awarded: Spring Semester, 2005. / Date of Defense: December 6, 2004. / Intersection crashes, older drivers, age, highway traffic safety, risk factors, younger drivers, fatal crash, case based analysis, non-intersection crashes / Includes bibliographical references. / Lisa K. Spainhour, Professor Directing Thesis; Virgil Ping, Committee Member; Yassir AbdelRazig, Committee Member.

In the Florida State highway system there are 11,100 bridges (6,300 State bridges and 4,800 local bridges). The highway system includes 98 movable bridges, which are located within seven geographic districts. These bridge decks are constructed with steel open metal grate decking to reduce the weight of the superstructure and load carried by the substructure. When traffic traverses on the bridge deck systems, a significant level of noise is generated. This noise has caused some discomfort and has become a nuisance to the public, especially in regard to those bridges located near populated areas. Because of the problem, it has been suggested that filling the open grate with epoxy and fine aggregate broadcasted on it will increase the friction resistance and reduce the noise from bridge deck systems. For new bridges, concrete filling (exodermic deck) has been used, taking the extra weight from the concrete into consideration during the design stage. For the older bridges, however, the extra concrete weight was not considered in the design stage. Thus, the use of epoxy materials, which are lighter than concrete, is necessary in existing decks in order to remain within the load-carrying capacity of the other components of the bridge. The primary objective of this study was to address the performance of the filled steel deck systems, the behavior and effect of repetitive thermal loads (temperatures below and above normal ambient temperature) to the open steel grid deck systems that were filled with epoxy resin. The deck systems filled with epoxy materials were subjected to accelerated climate chamber to simulate similar or extreme field conditions. Experimental results found that the performance of the open filled decks depends on the weather conditions. Under temperatures above normal ambient temperature, the interfacial region showed severe delamination compared to temperatures below normal ambient temperature. Also the study found that the performances at the interfacial region were affected by the number of cycles for both low and high temperatures. / A Thesis submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the Requirements for the degree of the Master of the science. / Degree Awarded: Fall Semester, 2006. / Date of Defense: August 11, 2006. / Bridge maintenance / Includes bibliographical references. / Primus V. Mtenga, Professor Directing Thesis; Kamal S. Tawfiq, Committee Member; John O. Sobanjo, Committee Member.

Thesis: S.M. in Transportation, Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 95-98). / Although automated data collection systems have been in existence long enough to be the subject of extensive research, they continue to transform both the agency and customer side of public transportation. Transit system performance is defined along three dimensions: the supply of trains or buses; the demand from passengers; and the product of the two, service performance. This research takes a broad view of these dimensions, and explores several means of measuring each one, ways in which they interact, and how this information can be valuable for a transit agency. This thesis focuses specifically on the London Underground, but the intent is that the types of analysis described herein can be applied to any rail transit system with similar data resources. The research has three parts. First, a methodology is developed to estimate passenger volumes on the portion of a line between two adjacent stations within a defined time interval. This approach can be implemented using data from either smart card or entry and exit gates. It relies upon the outputs of London's Rolling Origin Destination Survey to infer passenger route choice. The second component identifies the possible causes of poor service performance in terms of both supply and demand, and defines a framework for examining supply and demand data to identify which causes are contributors. This research suggests that a better understanding of capacity constraints can be gained by jointly analyzing AVL-based capacity measures, AFC-based demand measures, and AFC journey times as a measure of service performance. Finally, this thesis explores the possibility of using smart card data in real time to estimate system state. This metric is defined as passenger accumulation, a measure of the number of passengers on a given portion of a line in real time. Building from the approach developed in the first section, this work designs a method to determine accumulation in real time at detailed levels of spatial granularity. The accumulation metric is then compared to Transport for London's existing tools to assess whether accumulation can provide value as a real-time indicator of system state. Based on this analysis and current data availability constraints it cannot be concluded that passenger accumulation provides a reliable indicator of real-time system state. / by Lauren Tarte. / S.M. in Transportation

Thesis: S.M., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 44-46). / This paper presents an experimental study of the behavior of oil plumes in ambient stratification and a mild current, in which the flow is classified as stratification-dominated. Experiments are conducted in an inverted framework by releasing a continuous stream of dense glass beads from a carriage towed in a salt-stratified tank. Non-dimensional particle slip velocity UN ranged from 0.1 to 1.9. While particles of all sizes were affected by the stratification, only those with UN less or equal to 0.5 were observed to enter the intrusion layer. The spatial distributions of beads, collected on a bottom sled towed with the source, present a Gaussian distribution in the transverse direction and a skewed distribution in the along-current direction. Dimensions of the distributions increase with decreasing UN. The spreading relations can be used as input to far-field models describing subsequent transport. The average particle settling velocity, Uave, was found to exceed the individual particle slip velocity, Us, which is attributed to the initial plume velocity near the point of release. Additionally, smaller particles exhibit a "secondary plume effect" as they exit the intrusion as a swarm. The secondary effect becomes more prominent as UN decreases. These findings might explain the observations from the 2000 Deep Spill field experiment where oil was found to surface more rapidly than predicted based on Us. An analytical model predicting the particle deposition patterns, was developed based on findings above and validated against experimental measurements. The model estimates near-field oil transport under the Deepwater Horizon spill conditions, with and without chemical dispersants. / by Dayang Wang. / S.M.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1999. / Includes bibliographical references. / At present, very little is known about the mechanisms that control flow and transport through wetland deposits. Therefore, the objective of this research was to investigate the factors that influenced flow in wetland soils. To accomplish this, Column Experiments, run on a specialized permeameter, were conducted on both re-sedimented and undisturbed wetland soil specimens. During these experiments, sodium chloride (NaCl) tracer was injected into the soil specimen, and its breakthrough was monitored concurrently with other parameters, such as flow velocity and hydraulic gradient. Subsequently, the breakthrough data collected during the Column Experiments were fit using both the One-Region and Two-Region transport models, and the fit results were analyzed and compared to the geotechnical data collected for the soil. The data collected during the experimental program indicate enormous complexity in the mechanisms controlling flow and transport through wetland soils. From their analysis the following observations were made: First, even though wetland soils are considered to be two-region soils, having both an effective and an immobile porosity, the One-Region model was able to describe Sodium Chloride breakthrough in the soil. This indicates that the NaCl tracer was not interacting with the immobile region of the specimen. Second, the results demonstrated that wetland soil hydraulic conductivity is highly variable and sensitive to volume of flow. In fact, hydraulic conductivity was seen to decrease irreversibly by up to 6% per pore volume of flow. It was also found that hydraulic conductivity was sensitive to increases in pore water salt concentration, and to the flushing out of salts from wetland specimens. Finally, it was observed that, for the most part, large changes in hydraulic conductivity did not correspond to changes in the specimen's effective pore size or pore distribution. In fact, unless salt concentrations were increased drastically, the effective pore space remained invariant over an order of magnitude change in soil hydraulic conductivity. This suggests that changes in soil hydraulic conductivity might be due to increases or decreases in the number of flow channel constrictions in a specimen. From the results of this research it is hypothesized that the number of flow channel constrictions increased when flow and a decrease in salt concentration mobilized organic and mineral particles, which collected and clogged narrow pore throats along the flow channels. It is also hypothesized that the number of flow channel constrictions decreased when increases in pore water salt concentration causect organic fibers along the flow channel walls to coil. / by Lana A. Aref. / Sc.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1999. / Includes bibliographical references (p. 713-732). / Drilled shafts are widely used to transfer heavy structural loads (both axial and lateral) through the overburden soil to the underlying rock mass. It is important to consider the effect of discontinuities when designing drilled shafts in rock. This thesis develops (1) a new design method for axially loaded rock-socketed shafts; (b) new design methods for laterally loaded rock-socketed shafts; and (c) a method for assessing the three dimensional (30) geometric characteristics of discontinuities. The new design method for axially loaded rock-socketed shafts concentrates on the prediction of the ultimate side shear resistance and the end bearing capacity. New relations have been developed for both the side shear resistance and the end bearing capacity. Both developments are derived from the analysis of ex.tensive databases. For laterally loaded rock-socketed shafts, a simplified design method and a detailed design method were developed. The simplified design method assumes that the rock mass is isotropic and uses an elasto-plastic continuum model to predict the load-displacement response. This model can consider drilled shafts in rock overlain by soil and it was validated by comparing its results with available theoretical solutions and field test data. The detailed design method considers the effect of anisotropy of jointed rock masses. The key components of this method are the 30 geometric characterization of discontinuities and the estimation of the anisotropic defonnation and strength properties of jointed rock masses. The 30 characterization of discontinuities uses the observed trace data in a finite circular window (on an exposed outcrop or at the bottom of a shaft hole) to determine the corrected trace length distribution, the discontinuity size (diameter) distribution, the total number of discontinuities in an objective volume, and finally the fracture tensor which describes the intensity and orientation of all discontinuities in a rock mass. The method for estimating the anisotropic elastic deformation properties uses the superposhion-principle and adopts an equivalent continuum approach. Hill's criterion is used to describe the anisotropic yield/failure of jointed rock masses. The method was then applied to examine the effect of anisotropy on the lateral deformation of rock-socketed shafts. Also, design charts were developed for considering the effect of anisotropy when predicting the elastic defonnation of laterally loaded rock-socketed shafts. Finally, the applicability of the recommended design methods is discussed and a design example is presented. / by Lianyang Zhang. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1999. / Includes bibliographical references. / Sulfate reducing bacteria are believed to be the most important methylators of mercury in aquatic systems. Methylation may be controlled by the availability of mercury to these bacteria and therefore may depend on mercury speciation in sulfidic water ... / by Jennifer Ayla Jay. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1999. / Includes bibliographical references. / The goal of this thesis is to study the relationship between the community structure of marine microorganisms and nutrient availability. To this end, size spectra of microbes were studied over a range of nutrient regimes, both natural and manipulated. Three transects in the Atlantic provided a natural range of nutrient environments, especially because they captured seasonal variations. The transects encompassed Sargasso Sea, Gulf Stream, and coastal waters, during winter, spring, and summer. Nutrient regimes ranged from surface waters of the Sargasso Sea during stratified periods (low-nutrient), to deeply mixed waters in all three regions of the transects during winter and spring (high-nutrient). Complementing natural variations in nutrients, two experiments were used to study the effects of enrichment on size structure. An in situ iron-enrichment experiment conducted in the equatorial Pacific (IronEx II) provided a unique opportunity to monitor changes in community structure following increased nutrient availability. In a second experiment in the Sargasso Sea, enrichments with nitrogen and phosphorus were conducted in bottles, because one or both are commonly thought to be limiting in this region. In order to carry out the goal of this thesis, which depended on the use of flow cytometry to characterize bacterio-, pico-, ultra-, and nanophytoplankton, advancements were made in methods for enumerating a wide range of cell sizes and for estimating cell size from forward angle light scatter. In addition, because ambient concentrations of inorganic nitrogen and phosphorus are exceedingly low (<10nM) in the Atlantic, especially during stratified periods, low-level determinations of these nutrients were made to compliment the analyses of community structure. Size structure varied systematically, although not necessarily as a function of nutrient availability. Two parameters were explored: 1) spectral slope, which indicates the relative contribution of large and small cells to total biomass, and 2) spectral shape, or adherence of the spectra to relationships explained by a power law. The relative ranking of the slopes from specific regions of the transects remained constant throughout different seasons. Shapes ranged from discontinuous to those which adhered to a power law. It is hypothesized that only microbial systems with abundant nutrient inputs and, perhaps, reduced grazing pressure, have smooth spectra whose shapes conform to power laws. / by Kent Keller Cavender-Bares. / Ph.D.

Thesis: M. Eng., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 39-43). / A new inlet for studying the composition of mixed-phase clouds - the phaSe seParation Inlet for Droplets icE residuals and inteRstitial aerosols (SPIDER) - is described. SPIDER combines an omni-directional inlet, a Large-Pumped Counterflow Virtual Impactor (L-PCVI), a flow tube as evaporation chamber, and a Pumped Counterflow Virtual Impactor (PCVI) to separate droplets, ice crystals, and interstitial aerosols for simultaneous sampling. Verification tests of each individual component of SPIDER were positive, as was the result of investigating that the components work together as a whole setup without flow blockage or choking. SPIDER was installed at Mt. Washington Observatory (MWO), a mountain top research facility in the White Mountains, for a two-week field campaign. There, SPIDER showed promising performance as a field instrument and provided first data that suggest its capability of separating distinct cloud particles. Future design improvements of SPIDER are suggested along with potential locations for field measurements. / by Libby Koolik. / M. Eng.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, February 2007. / Includes bibliographical references (p. 127-131). / The goal of this research is to develop an improved understanding of supply chain management strategies and practices being pursued by Boeing and Airbus in the 787 Dreamliner and the A380 Navigator programs, respectively, and to identify their long-term strategic implications for supply chain management in the future. The research takes as its point of departure a review and synthesis of supply chain management principles and practices, with particular emphasis on lean supply chain management concepts. Guided by this review, the research focuses on the common set of suppliers supporting both programs and employs a questionnaire survey, followed by telephone interviews with representatives of selected suppliers. The research also makes extensive use of the open source information on both companies, on both programs and on the common suppliers. / (cont.) A major finding is that Boeing's new supply chain model in the 787 program represents a significant break with past practices in the aerospace industry, allowing major partnering suppliers an unprecedented role in terms of design, development, production and after-market support, where they are integrated early in the concept development stage and are incentivized to collaborate with Boeing, as well as among themselves, as risk-sharing partners with deep responsibility for system integration, involving detailed interface control at the system and subsystem levels. Airbus, as well, is found to rely heavily on its major suppliers in connection with the A380 program, but acting as the primary system integrator in the more traditional mode and exercising much greater control of all design interfaces. Also, both Boeing and Airbus have been outsourcing more and more activities to suppliers located in non-traditional regions, such as Eastern Europe and the Asia-Pacific region. Finally, aerospace manufacturers, in general, are aggressively adopting information technologies (e.g., EDI, PLM, 3-D Digital Model, RFID) to facilitate greater data sharing and communications with their partners and lower-tier suppliers dispersed in many geographical regions, as part of a broader trend involving more collaborative supplier relationships reaching down to the subtier level. / by Tzu-Ching Horng. / S.M.