Simulating the Impact of Traffic Calming Strategies

This study assessed the impact of traffic calming measures to the speed, travel times and capacity of residential roadways. The study focused on two types of speed tables, speed humps and a raised crosswalk. A moving test vehicle equipped with GPS receivers that allowed calculation of speeds and determination of speed profiles at 1s intervals were used. Multi-regime model was used to provide the best fit using steady state equations; hence the corresponding speed-flow relationships were established for different calming scenarios. It was found that capacities of residential roadway segments due to presence of calming features ranged from 640 to 730 vph. However, the capacity varied with the spacing of the calming features in which spacing speed tables at 1050 ft apart caused a 23% reduction in capacity while 350-ft spacing reduced capacity by 32%. Analysis showed a linear decrease of capacity of approximately 20 vphpl, 37 vphpl and 34 vphpl when 17 ft wide speed tables were spaced at 350 ft, 700 ft, and 1050 ft apart respectively. For speed hump calming features, spacing humps at 350 ft reduced capacity by about 33% while a 700 ft spacing reduced capacity by 30%. The study concludes that speed tables are slightly better than speed humps in terms of preserving the roadway capacity. Also, traffic calming measures significantly reduce the speeds of vehicles, and it is best to keep spacing of 630 ft or less to achieve desirable crossing speeds of less or equal to 15 mph especially in a street with schools nearby. A microscopic simulation model was developed to replicate the driving behavior of traffic on urban road diets roads to analyze the influence of bus stops on traffic flow and safety. The impacts of safety were assessed using surrogate measures of safety (SSAM). The study found that presence of a bus stops for 10, 20 and 30 s dwell times have almost 9.5%, 12%, and 20% effect on traffic speed reductions when 300 veh/hr flow is considered. A comparison of reduction in speed of traffic on an 11 ft wide road lane of a road diet due to curbside stops and bus bays for a mean of 30s with a standard deviation of 5s dwell time case was conducted. Results showed that a bus stop bay with the stated bus dwell time causes an approximate 8% speed reduction to traffic at a flow level of about 1400 vph. Analysis of the trajectories from bust stop locations showed that at 0, 25, 50, 75, 100, 125, 150, and 175 feet from the intersection the number of conflicts is affected by the presence and location of a curbside stop on a segment with a road diet

Video based vehicle detection for advance warning Intelligent Transportation System

Video based vehicle detection and surveillance technologies are an integral part of Intelligent Transportation System (ITS), due to its non-intrusiveness and capability or capturing global and specific vehicle behavior data. The initial goal of this thesis is to develop an efficient advance warning ITS system for detection of congestion at work zones and special events based on video detection. The goals accomplished by this thesis are: (1) successfully developed the advance warning ITS system using off-the-shelf components and, (2) Develop and evaluate an improved vehicle detection and tracking algorithm. The advance warning ITS system developed includes many off-the-shelf equipments like Autoscope (video based vehicle detector), Digital Video Recorders, RF transceivers, high gain Yagi antennas, variable message signs and interface processors. The video based detection system used requires calibration and fine tuning of configuration parameters for accurate results. Therefore, an in-house video based vehicle detection system was developed using the Corner Harris algorithm to eliminate the need of complex calibration and contrasts modifications. The algorithm was implemented using OpenCV library on a Arcom\u27s Olympus Windows XP Embedded development kit running WinXPE operating system. The algorithm performance is for accuracy in vehicle speed and count is evaluated. The performance of the proposed algorithm is equivalent or better to the Autoscope system without any modifications to calibration and lamination adjustments

In Situ Monitoring of Free-Phase Gas Accumulation and Release in Peatlands Using Ground Penetrating Radar (GPR)

We tested a set of surface common mid-point (CMP) ground penetrating radar (GPR) surveys combined with elevation rods ( to monitor surface deformation) and gas flux measurements to investigate in-situ biogenic gas dynamics and ebullition events in a northern peatland ( raised bog). The main findings are: ( 1) changes in the two-way travel time from the surface to prominent reflectors allow estimation of average gas contents and evolution of free-phase gas (FPG); ( 2) peat surface deformation and gas flux measurements are strongly consistent with GPR estimated changes in FPG content over time; ( 3) rapid decreases in atmospheric pressure are associated with increased gas flux; and ( 4) single ebullition events can induce releases of methane much larger ( up to 192 g/m(2)) than fluxes reported by others. These results indicate that GPR is a useful tool for assessing the spatial distribution, temporal variation, and volume of biogenic gas deposits in peatlands

Optimization of path based sensor spacing on a freeway segment for travel time prediction during incidents

Congestion on freeways is increasing and a key source of it is non-recurring incidents. Accurate vehicle travel time predictions are needed during these incidents in order for roadway users to make informed trip decisions. Path based sensors are becoming a leading technology in gathering real-time travel time data. The data is used to make travel time predictions that are then provided through various means, such as dynamic message signs, to roadway users. These types of sensor are located at stationary points along a roadway and collect individual vehicle travel time data from vehicles as they drive pass the sensors. The accuracy of the predictions, in terms of representing future travel times, is dependent on many factors including the sensor spacing along the roadway, the duration and location of a traffic incident, and the uncongested and congested traffic speeds and traffic flows. Understanding the relationship between the travel time prediction accuracy and the different variables is necessary to optimize sensor spacing. In addition, because incidents occur at different times of the day, have varying durations, occur at different locations, and cause different capacity reductions depending on the severity of the incident, the sensor spacing cannot be based on one incident scenario. Instead, multiple incident scenarios, along with the probability of each occurring, needs to be taken into account. Path based sensor spacing during incidents on a freeway segment is optimized in this dissertation. In addition, the marginal benefit of additional sensors is calculated. A mathematical model and a solution methodology are developed. The mathematical model applies macroscopic traffic principles and shock wave theory. It calculates the travel time prediction error by sensor spacing during an incident on a freeway segment. The solution algorithm consists of four main steps. First, historical incident data for the roadway are gathered. Second, the mathematical model is applied to determine the average travel time prediction error by sensor spacing for each of the historical incidents. Third, the weighted average travel time prediction error by sensor spacing is calculated, which considers all the possible incidents and the frequency of each occurring. Fourth, the optimal spacing is chosen which minimizes the weighted average error. The applicability of the model and solution methodology is demonstrated through a case study of a ten mile freeway segment in Northern New Jersey

Optimisation of the End-To-End Phantom for Real-time High Dose Rate Prostate Brachytherapy Verification

High dose rate (HDR) brachytherapy is a form of close range radiotherapy whereby dose is delivered by means of an internal radiation source. By doing so, a high level of dose con-formity and accuracy can be achieved. However, due to the high source activity coupled with the close proximity of radio-sensitive organs such as the rectum, bladder and urethra, there exists the potential of incorrect dose delivery; the irradiation of these organs may con-sequently lead to post-treatment complications. As a result, the need for accurate forms of quality assurance methodology which can verify different aspects of the treatment delivery is paramount. These methodologies must be able to perform real-time dose analysis to monitor crucial organ exposure as well as accurately localise the HDR source within space to verify its position according to the treatment plan. An End-to-end Phantom was developed with anatomically correct Gel Prostate phantoms to create an anthropomorphic representation of the clinical environment. This allowed the testing of clinically relevant treatment plans on the MP987 detector system to test its source localisation capabilities. It was shown that when comparing to the TPS defined dwell po-sitions, the system was able to determine positions on average to within (3.69±0.14)mm,(3.70±0.15)mm, (3.53±0.12)mm and (0.30±0.06)s for the x, y, z and t coordinates respec-tively

Quantifying the Impact of Weather Events on Travel Time and Reliability

It is of practical significance to understand the specific impact of weather events on the operating condition of the surface transportation system so that proactive and reactive strategies can be quickly implemented by transportation agencies to minimize the negativity resulted from adverse weather events. Many studies have been conducted on quantifying such effects yet suffer from limitations such as subjectively defining a time window under uncongested conditions and not being able to account for the severe impact from weather events which result in travel time unreliability. To overcome those shortcomings in existing literature, an integrated data mining framework based on decision tree and quantile regression techniques is developed in this study. The results demonstrate that the approach is effective in characterizing time periods with different traffic characteristics and quantifying the impact of rain and snow events on both congestion and reliability aspects of the transportation system. It is observed that snow events impose more significant impact on travel times than that from rain events. In addition, the impact from weather events is even more severe on travel time reliability than average delay. The impact magnitude is directly related to the level of recurrent congestion under study. Other insights with regard to the capability of quantile regression and future improvement on the methodological design are also offered

Rifting in the northern Tyrrhenian Sea Basin: a multichannel and wide-angle seismic study

Rifted continental margins or basins are the results of continental lithospheric extension and a fundamental process in geodynamics. Extension is expressed by normal faulting and block rotation in the brittle upper crust and ductile deformation in the lower crust. Conjugate rifted margins are often asymmetric and reveal different amounts of crustal stretching and thinning. Shallow dipping crustal-scale detachment faults are thought to be the controlling mechanism of this asymmetry, although the development of such features is debated. This PhD thesis presents the results of a seismic campaign from the northern Tyrrhenian Sea Basin. It is a continental back-arc basin exhibiting rift features preserved at the early stages of rifting. Two W-E orientated multichannel seismic profiles (MCS) cross the region between Corsica, Sardinia and mainland Italy. The data are processed up to prestack-depth and time migrated images in order to investigate the style of faulting and sedimentary structures. Coincident refraction- and wide-angle seismic data were acquired using OBH-stations. Joint refraction and reflection tomography reveal the crustal architecture and thickness. The MCS image of the northern profile shows that the geometry of upper Tortonian to Early-Pliocene sediments (8-4 Ma) reflects the active rift phase. Fault displacements are localized on major normal faults dipping mainly to the east (30°-40°) forming a succession of asymmetric half-grabens. Major blocks generate the majority of the entire horizontal extension which is estimated to be ~30%. Faults seem not to be linked at the brittle-ductile transition zone (~3-4 km). The tomographic model shows, that the crust has thinned from ~24 km to a thickness of ~17 km (ß=1.3). The thinning matches the estimated amount of horizontal extension (30%). Towards the southern transect, the width of the basin increases. Seismic data display an asymmetric margin configuration. This is expressed by crustal thinning from ~24 km in the west (Sardinia) to ~11 km in the east (ß-factor=2.2). Moreover, the Sardinia Margin comprises large fault-bounded blocks where the crust is relatively thick. Blocks of smaller size are observed further east, where the crust has thinned more. This zone (~ 100 km wide) is characterized by reduced p-wave velocities which correlates with intensive faulting as imaged on the MCS section. A reliable estimation of the amount of brittle extension is not possible due to the presence of complex small-scale faults. However, the thinning-factor of the lower crust matches the thinning-factor of the entire crust. This implies that the amount of brittle extension should be similar. In this zone, reflections within sedimentary sub-basins are related to basalt flows. A narrow zone with similar characteristics is also observed on the northern line. In the vicinity of the Sardinia Margin, post-rift sediments indicate that tectonism has ceased before Early-Pliocene time, whereas young faults cut the seafloor in the center and in the eastern region (near mainland Italy). The different ages of syn-tectonic sequences indicate an apparent W-E rift propagation. The comparison of both transects shows a NW-SE orientated crustal thinning resulting in mantle exhumation in the Vavilov Basin. Diminishing block sizes and concomitant crustal thinning reflect increasing strain rates in NW-SE direction. The data provide no evidence for potential long-lived detachment faults controlling the development of the asymmetric rift configuration. However, it can be explained by the regional plate-tectonic setting and subduction roll-back. Rifting propagated toward the east, following the retreatment of the subduction zone. The pole of rotation is located north of the basin. Thus, with increasing distance from the pole toward the south, stretching rates increase. This led to the differences of syn-sedimentary ages, block sizes and NW-SE crustal thinning

Initial characterization of coagulin polymerization and a novel trypsin inhibitor from Limulus polyphemus

In the final step of coagulation in the horseshoe crab, coagulogen (M\sb{\rm w} = 19,000, from sedimentation equilibrium) is converted by discrete proteolysis into its clottable form, coagulin. Coagulogen does not have a strong tendency to self-associate. In 0.1 M ammonium bicarbonate, 50 mM Tris-HCL (pH 8.1), trypsin generated coagulin rapidly associates to form a stable, solid gel. Polymerization is pH-dependent, with reversible depolymerization occurring in acid (midpoint pH 5.4). Sedimentation velocity analysis reveals that stable intermediates remain at pH 2.5, with 30-31 s being the predominant form along with monomer (1.89 s) and larger forms ($\u3e$60 s). Near the midpoint of the titration, a pressure-dependent association occurs with a distribution of very large species resulting. There is also evidence that at this point a concurrent pressure-dependent depolymerization is occurring. Trypsin inhibitory activity from the hemolymph of Limulus polyphemus was found to co-purify with coagulogen in my preparations. Limulus trypsin inhibitor (LTI) was separated from coagulogen by ion-exchange chromatography on carboxymethyl-Sephadex. A molecular weight of 16,300 was determined by analytical ultracentrifugation. This value is consistent with estimates from SDS-PAGE and amino acid composition. The amino-terminal sequence consists primarily of hydrophobic amino acid residues. LTI was found to inhibit the action of trypsin on both high and low molecular weight substrates. It also inhibits chymotrypsin but has little or no effect on thrombin, thermolysin, pepsin, or papain. Comparison of the amino acid composition and amino-terminal sequence of LTI with those of other known trypsin inhibitors revealed no significant similarity to other trypsin inhibitors, suggesting it may represent a new class of proteinase inhibitors