Update: Percentage of young persons with a driver's license continues to drop

In two previous studies, we have shown that in several countries, including the United States, the percentage of young persons with a driver's license has recently decreased substantially. In this update, we extend the analysis for the United States--originally performed for 1983 and 2008-through 2010 by using driver-license and general-population data from the Federal Highway Administration and the U.S. Census Bureau. The results indicate that the general trend continues. For example, the percentages of persons 19 years of age with a driver's license in 1983, 2008, and 2010 were 87.3, 75.5, and 69.5, respectively.     

Processing and analysis of roadway runoff micro (< 20 μm) particles

This study was performed to compare paper and sieving filtration methods for processing micro particles (< 20 μm) in roadway runoff for water quality evaluation. The consequence of a lack of reliable particle processing on particle number, particle concentration and particulate elemental composition, as well as their influence on particle mass and pollutant load calculations, is discussed. Results show that the paper filtering method can affect the measurement of particle size distributions of highway runoff samples. Contrary to common practice, it is not always correct to assume that the number and concentration of particles < 38 μm is the same as the number and concentration of particles < 20 μm. Processed samples for micro particles were most similar to unprocessed samples when nylon sieves were used. Samples filtered by paper deviated significantly from unprocessed samples. These deviations can cause inaccuracies up to 90 percent, in particle count and concentration, TSS calculations, elemental mass composition, and particle and elemental mass loading.     

Body-pillar vision obstructions and lane-change crashes

INTRODUCTION: This exploratory study investigated the relationship between vision obstructions from body pillars and lane-change crashes. METHODS: The vision obstructions were quantified by measuring, from the driver's perspective, the horizontal angular sizes and locations of the driver-side A-, B-, and C-pillars. The sample consisted of 21 vehicle models, including 13 passenger cars, 6 SUVs, 1 minivan, and 1 pickup truck. To control for driver differences, going-straight crashes were used for comparison, with the dependent variable being the ratio of lane-change crashes to going-straight crashes. The analysis used North Carolina crash data. RESULTS: The results of a multiple regression indicate that the relative frequency of lane-change crashes tended to increase with both wider A-pillars and with A-pillars located farther away from straight ahead. IMPACT ON INDUSTRY: The finding supports the hypothesis that visibility obstructions due to A-pillars have safety implications.     

Optimal strategies for adaptive curve lighting

PROBLEM: Conventional low beams headlamps do not provide sufficient illumination for nighttime visibility on curves. METHOD: This analytical study evaluated the advantages and disadvantages of several curve-lighting strategies that involve moving one or both low beams by various amounts. Two curve radii were examined for both curve directions, using representative tungsten-halogen and high-intensity discharge low-beam patterns. The dependent variable was the maximum distance of 3-lux illumination (combined from both lamps) at a plane 0.25 m above the roadway for seven lateral positions. RESULTS: For short-radius, left and right curves, moving both lamps in parallel should substantially increase the visibility of objects in one's lane of travel, in several additional lanes of travel to the left and right, and off the road. DISCUSSION: Because of the lateral trade-offs of advantages and disadvantages for large-radius curves, additional research is needed to better understand the desirable approach for these types of curves. IMPACT ON INDUSTRY: Moving both lamps in parallel into the curve is recommended for small-radius curves.     

Optimum swimming pathways of fish spawning migrations in rivers

Fishes that swim upstream in rivers to spawn must navigate complex fluvial velocity fields to arrive at their ultimate locations. One hypothesis with substantial implications is that fish traverse pathways that minimize their energy expenditure during migration. Here we present the methodological and theoretical developments necessary to test this and similar hypotheses. First, a cost function is derived for upstream migration that relates work done by a fish to swimming drag. The energetic cost scales with the cube of a fish's relative velocity integrated along its path. By normalizing to the energy requirements of holding a position in the slowest waters at the path's origin, a cost function is derived that depends only on the physical environment and not on specifics of individual fish. Then, as an example, we demonstrate the analysis of a migration pathway of a telemetrically tracked pallid sturgeon (Scaphirhynchus albus) in the Missouri River (USA). The actual pathway cost is lower than 10(5) random paths through the surveyed reach and is consistent with the optimization hypothesis. The implication--subject to more extensive validation--is that reproductive success in managed rivers could be increased through manipulation of reservoir releases or channel morphology to increase abundance of lower-cost migration pathways.     

Production and perception of situationally variable alarm calls in wild tufted capuchin monkeys (Cebus apella nigritus)

Many mammalian and avian species produce conspicuous vocalizations upon encountering a predator, but vary their calling based on risk urgency and/or predator type. Calls falling into the latter category are termed “functionally referential” if they also elicit predator-appropriate reactions in listeners. Functionally referential alarm calling has been well documented in a number of Old World monkeys and lemurs, but evidence among Neotropical primates is limited. This study investigates the alarm call system of tufted capuchin monkeys (Cebus apella nigritus) by examining responses to predator and snake decoys encountered at various distances (reflecting differences in risk urgency). Observations in natural situations were conducted to determine if predator-associated calls were given in additional contexts. Results indicate the use of three call types. “Barks” are elicited exclusively by aerial threats, but the call most commonly given to terrestrial threats (the “hiccup”) is given in nonpredatory contexts. The rate in which this latter call is produced reflects risk urgency. Playbacks of these two call types indicate that each elicits appropriate antipredator behaviors. The third call type, the “peep,” seems to be specific to terrestrial threats, but it is unknown if the call elicits predator-specific responses. “Barks” are thus functionally referential aerial predator calls, while “hiccups” are better seen as generalized disturbance calls which reflect risk urgency. Further evidence is needed to draw conclusions regarding the “peep.” These results add to the evidence that functionally referential aerial predator alarm calls are ubiquitous in primates, but that noncatarrhine primates use generalized disturbance calls in response to terrestrial threats.     

Batch reactor kinetic studies on the reductive dechlorination of chlorinated ethylenes by tetrakis-(4-sulfonatophenyl)porphyrin cobalt

Tetrakis-(4-sulfonatophenyl)porphyrin cobalt was identified as a highly-active reductive dechlorination catalyst for chlorinated ethylenes. Through batch reactor kinetic studies, degradation of chlorinated ethylenes proceeded in a step-wise fashion with the sequential replacement of Cl by H. For perchloroethylene (PCE) and trichloroethylene (TCE), the dechlorination products were quantified and the C₂ mass was accounted for. Degradation of the chlorinated ethylenes was found to be first-order in substrate. Dechlorination trials with increasing catalyst concentration showed a linearly increasing pseudo first-order rate constant which yielded rate laws for PCE and TCE degradation that are first-order in catalyst. The dechlorination activity of this catalyst was compared to that of another water-soluble cobalt porphyrin under the same reaction conditions and found to be comparable for PCE and TCE.     

Borehole‐scale testing of matrix diffusion for contaminated‐rock aquifers

A new method was developed to assess the effect of matrix diffusion on contaminant transport and remediation of groundwater in fractured rock. This method utilizes monitoring wells constructed of open boreholes in the fractured rock to conduct backward diffusion experiments on chlorinated volatile organic compounds (CVOCs) in groundwater. The experiments are performed on relatively unfractured zones (called test zones) of the open boreholes over short intervals (approximately 1 meter) by physical isolation using straddle packers. The test zones were identified with a combination of borehole geophysical logging and chemical profiling of CVOCs with passive samplers in the open boreholes. To confirm the test zones are within inactive flow zones, they are subjected to a series of hydraulic tests. Afterward, the test zones are air sparged with argon to volatilize the CVOCs from aqueous to air phase. Backward diffusion is then measured by periodic passive‐sampling of water in the test zone to identify rebound. The passive (nonhydraulically stressed) sampling negates the need to extract water and potentially dewater the test zone. The authors also monitor active flowing zones of the borehole to assess trends in concentrations in other parts of the fractured rock by purge and passive sampling methods. The testing was performed at the former Pease Air Force Base (PAFB) in Portsmouth, New Hampshire. Bedrock at the former PAFB consists of fractured metasedimentary rocks where the authors investigated back diffusion of cis‐1,2‐dichloroethylene (cis‐1,2‐DCE), a CVOC. Postsparging concentrations of cis‐1,2‐DCE showed initial rebounding followed by declines, excluding an episodic spike in concentrations from a groundwater recharge event. The authors theorize that there are three processes that controlled concentration responses in the test zones postsparging. First, the limited back diffusion of CVOCs from a halo or thin zone of rock around the borehole contributes to the initial rebounding. Second, aerobic degradation of cis‐1,2‐DCE occurred causing declines in concentrations in the test zone. Third, microflow from microfractures contributed to the episodic spike in concentrations following the groundwater recharge event. In active flow zones, the latter two processes are not measurable due to equilibration from groundwater transport between the borehole and active flowing fractures.