The Effect of Roadside Elements on Driver Behavior and Run-Off-the-Road Crash Severity

Roadside vegetation provides numerous environmental and psychological benefits to drivers. Previous studies have shown that natural landscapes can effectively lower crash rates and cause less stress and frustration to the driver. However, run-off-the-road crashes resulting in a collision with a tree are twice as likely to result in a fatality, thus reinforcing the need to examine the placement of vegetation within the clear zone. This study explores the relationship between the size of the clear zone and the presence of roadside vegetation on selected driver attributes, including both driver speed and lateral positioning. To evaluate the effect on the driver speed selection process, a static evaluation was employed. Completed by more than 100 drivers, the static evaluation was utilized to gather speed selections on both real and virtual roads containing four combinations of clear zone size and roadside vegetation density. Additionally, field data was collected to validate the findings of the static evaluation and to determine the extent to which roadside vegetation impacts driving attributes. When presented with a large clear zone, drivers positioned the vehicle further from the edge of the road as the vegetation density increased. Furthermore, the speeds observed in the field correlated with the speeds that participants selected when watching a video of the same road. Finally, the UMassSafe Traffic Safety Data Warehouse was utilized to link crash and roadway data, allowing for an in-depth analysis of run-off-the-road (ROR) crash severity. The results of this study further demonstrate the nature of the relationship between clear zone design and driver behavior

Evaluating the Impacts of Driver Behavior in the Speed Selection Process and the Related Outcomes

In the United States, traffic crashes claim the lives of 30,000 people every year and is the leading cause of death for 5-24 year olds. Driver error is the leading factor in over 90 percent of motor vehicle crashes, with the roadway and the vehicle each only accounting for about 2 percent of crashes. In the United States, nearly a third of fatal crashes are due to speeding and therefore, a critical step in improving traffic safety is research aimed to reduce speeding, such as crash data analysis, outreach campaigns, targeted enforcement, and understanding speed selection. In this dissertation, a multi-faceted approach was taken to improve roadway safety by examining the speeding-related crash designation, improving speed limit setting practices, and understanding the causes of speeding. Multiple experiments were conducted under this overarching goal. These experiments included an analysis of speeding-related crashes in Massachusetts, a naturalistic driving study, and a driving simulator study which investigated the causes of speeding. Collectively, the findings from these experiments can expand upon existing speed prediction models, improve crash data influence speed limit setting practices, guide speed management programs such as speed enforcement, and be used in public safety outreach campaigns

The Structure of the Large Magellanic Halo Stellar Halo Derived Using OGLE-III RR Lyr stars

We use the recently released OGLE-III catalog of 17692 fundamental mode RR Lyr (RRab) stars in the Large Magellanic Cloud (LMC) to investigate the structure of its stellar halo. We apply conservative cuts in period, amplitude and magnitude to remove blends and other contamination. We use period--luminosity and period--color relations to determine distance and extinction of every star in our final sample of 9393 stars. In order to determine the scatter of our method, we compare the distributions of distances in two regions at the edges of the covered area with a central region. We determine the intrinsic line-of-sight dispersion in the center to be 0.135 mag or 3.21 kpc (FWHM of 0.318 mag or 7.56 kpc), assuming zero depth in one of the edge regions. The conservative cuts we apply reduce the derived depth significantly. Furthermore, we find that the distribution of RRab stars is deformed in the sense that stars on the Eastern side are closer than on the Western side. We model the RRab distribution as a triaxial ellipsoid and determine its axes ratios to be 1:2.00:3.50 with the longest axis inclined by 6 degrees from the line of sight. Another result of our analysis is an extinction map of the LMC and a map of internal reddening, which we make publicly available.Comment: Accepted for publication in November 2009 issue of ApJ. 7 pages, 5 figures. Extinction map of the LMC available at http://www.astronomy.ohio-state.edu/~pejcha/lmc_extma

Radio Frequency Nonionizing Radiation in a Community Exposed to Radio and Television Broadcasting

Exposure to radio frequency (RF) nonionizing radiation from telecommunications is pervasive in modern society. Elevated disease risks have been observed in some populations exposed to radio and television transmissions, although findings are inconsistent. This study quantified RF exposures among 280 residents living near the broadcasting transmitters for Denver, Colorado. RF power densities outside and inside each residence were obtained, and a global positioning system (GPS) identified geographic coordinates and elevations. A viewshed model within a geographic information system (GIS) characterized the average distance and percentage of transmitters visible from each residence. Data were collected at the beginning and end of a 2.5-day period, and some measurements were repeated 8–29 months later. RF levels logged at 1-min intervals for 2.5 days varied considerably among some homes and were quite similar among others. The greatest differences appeared among homes within 1 km of the transmitters. Overall, there were no differences in mean residential RF levels compared over 2.5 days. However, after a 1- to 2-year follow-up, only 25% of exterior and 38% of interior RF measurements were unchanged. Increasing proximity, elevation, and line-of-sight visibility were each associated with elevated RF exposures. At average distances from > 1–3 km, exterior RF measurements were 13–30 times greater among homes that had > 50% of the transmitters visible compared with homes with ≤ 50% visibility at those distances. This study demonstrated that both spatial and temporal factors contribute to residential RF exposure and that GPS/GIS technologies can improve RF exposure assessment and reduce exposure misclassification

Detached binaries in the Large Magellanic Cloud. A selection of binaries suitable for distance determination

As a result of a careful selection of eclipsing binaries in the Large Magellanic Cloud using the OGLE-II photometric database, we present a list of 98 systems that are suitable targets for spectroscopic observations that would lead to the accurate determination of the distance to the LMC. For these systems we derive preliminary parameters combining the OGLE-II data with the photometry of MACHO and EROS surveys. In the selected sample, 58 stars have eccentric orbits. Among these stars we found fourteen systems showing apsidal motion. The data do not cover the whole apsidal motion cycle, but follow-up observations will allow detailed studies of these interesting objects.Comment: 15 pages, 6 figures, accepted for publication in A&

Evaluating the Safety Impacts of Flashing Yellow Permissive Left-Turn Indications in Massachusetts: Approach-Level Analysis

Given the novelty of the Flashing Yellow Arrow (FYA) in Massachusetts, this research study provides MassDOT with a greater understanding of their impacts from an approach-level perspective. More so, this study provides the agency with a holistic overview of infrastructure and operational impacts at each of these intersections, ultimately leading to an improved understanding of future design characteristics. Approach-level analyses remain the most appropriate method to assess the true impact of the permissive indication as well as infrastructure (e.g., turn lane length, LT lane offset, etc.) and operational (e.g., clearance intervals, phase sequence, etc.) elements. This study evaluated the before and after crashes at 200 statewide FYA intersections from an approach level to better understand the safety impacts of the LT permissive FYA signal. The advancement of these crash data analytics, methodologies, and applications will continue to remain important in years to come and will increase safety by providing an increased understanding of conflict risk at signalized intersections involving FYAs

Survey of O VI absorption in the Large Magellanic Cloud

We present a survey of interstellar O VI absorption in the Large Magellanic Cloud (LMC) towards 70 lines of sight based on Far Ultraviolet Spectroscopic Explorer (FUSE) observations. The survey covers O VI absorption in a large number of objects in different environmental conditions of the LMC. Overall, a high abundance of O VI is present in active and inactive regions of the LMC with mean log[N(O VI)] = 14.23 atoms cm$^{-2}$. There is no correlation observed between O VI absorption and emissions from the hot gas (X-ray surface brightness) or the warm gas (H$_{\alpha}$ surface brightness). O VI absorption in the LMC is patchy and the properties are similar to that of the Milky Way (MW). In comparison to the Small Magellanic Cloud (SMC), O VI is lower in abundance even though SMC has a lower metallicity compared to the LMC and the MW. We present observations in 10 superbubbles of the LMC of which we detect O VI absorption in 5 superbubbles for the first time and the superbubbles show an excess O VI absorption of about 40% compared to non-superbubble lines of sight. We have also studied the properties of O VI absorption in the 30 Doradus region. Even though O VI does not show any correlation with X-ray emission for the LMC, a good correlation between log[N(O VI)] and X-ray surface brightness for 30 Doradus region is present. We also find that O VI abundance decreases with increasing distance from the star cluster R136.Comment: 25 pages, 9 figures. Accepted for publication in MNRA

Identifying the progenitors of present-day early-type galaxies in observational surveys: correcting `progenitor bias' using the Horizon-AGN simulation

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. © 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.As endpoints of the hierarchical mass-assembly process, the stellar populations of local earlytype galaxies encode the assembly history of galaxies over cosmic time. We useHorizon-AGN, a cosmological hydrodynamical simulation, to study the merger histories of local early-type galaxies and track how the morphological mix of their progenitors evolves over time. We provide a framework for alleviating 'progenitor bias' - the bias that occurs if one uses only early-type galaxies to study the progenitor population. Early types attain their final morphology at relatively early epochs - by z ~ 1, around 60 per cent of today's early types have had their last significant merger. At all redshifts, the majority of mergers have one late-type progenitor, with late-late mergers dominating at z > 1.5 and early-early mergers becoming significant only at z < 0.5. Progenitor bias is severe at all but the lowest redshifts - e.g. at z~0.6, less than 50 per cent of the stellar mass in today's early types is actually in progenitors with early-type morphology, while, at z~ 2, studying only early types misses almost all (80 per cent) of the stellar mass that eventually ends up in local early-type systems. At high redshift, almost all massive late-type galaxies, regardless of their local environment or star formation rate, are progenitors of local early-type galaxies, as are lowermass (M* < 10 10.5 M ⊙) late-types as long as they reside in high-density environments. In this new era of large observational surveys (e.g. LSST, JWST), this study provides a framework for studying how today's early-type galaxies have been built up over cosmic time.Peer reviewe

Population effects on the red giant clump absolute magnitude: The K-band

We present a detailed analysis of the behaviour of the Red Clump K-band absolute magnitude (M(K,RC)) in simple and composite stellar populations, in light of its use as standard candle for distance determinations. The advantage of using M(K,RC), following recent empirical calibrations of its value for the solar neighbourhood, arises from its very low sensitivity to the extinction by interstellar dust. We provide data and equations which allow the determination of the K-band population correction Delta(M(K,RC)) (difference between the Red Clump brightness in the solar neighbourhood and in the population under scrutiny) for any generic stellar population. These data complement the results presented in Girardi & Salaris(2001) for the V- and I-band. We show how data from galactic open clusters consistently support our predicted Delta(M(V,RC)), Delta(M(I,RC)) and Delta(M(K,RC)) values. Multiband VIK population corrections for various galaxy systems are provided. They can be used in conjunction with the method devised by Alves et al.(2002), in order to derive simultaneously reddening and distance from the use of VIK observations of Red Clump stars. We have positively tested this technique on the Galactic globular cluster 47Tuc, for which both an empirical parallax-based main sequence fitting distance and reddening estimates exist. We have also studied the case of using only V and I photometry, recovering consistent results for both reddening and distance. Application of this method to an OGLE-II field, and the results by Alves et al.(2002), confirm a LMC distance modulus of about 18.50, in agreement with the HST extragalactic distance scale zero-point. (abridged)Comment: 9 pages, 8 figures, MNRAS accepte