California Department of Transportation

The NGA‐West2 project database expands on its predecessor to include worldwide ground motion data recorded from shallow crustal earthquakes in active tectonic regimes post‐2000 and a set of small‐to‐moderate‐magnitude earthquakes in California between 1998 and 2011. The database includes 21,336 (mostly) three‐component records from 599 events. The parameter space covered by the database is M 3.0 to M 7.9, closest distance of 0.05 to 1,533 km, and site time‐averaged shear‐wave velocity in the top 30 m of V S 30 = 94 m/s to 2,100 m/s (although data becomes sparse for distances >400 km and V S 30 > 1,200 m/s or <150 m/s). The database includes uniformly processed time series and response spectral ordinates for 111 periods ranging from 0.01 s to 20 s at 11 damping ratios. Ground motions and metadata for source, path, and site conditions were subject to quality checks by ground motion prediction equation developers and topical working groups.

We present an update to our 2008 NGA model for predicting horizontal ground motion amplitudes caused by shallow crustal earthquakes occurring in active tectonic environments. The update is based on analysis of the greatly expanded NGA‐West2 ground motion database and numerical simulations. The updated model contains minor adjustments to our 2008 functional form related to style of faulting effects, hanging wall effects, scaling with the depth to top of rupture, scaling with sediment thickness, and the inclusion of additional terms for the effects of fault dip and rupture directivity. In addition, we incorporate regional differences in far‐source distance attenuation and site effects between California and other active tectonic regions. Compared to our 2008 NGA model, the predicted medians by the updated model are similar for M > 7 and are lower for M < 5. The aleatory variability is larger than that obtained in our 2008 model.

We present a model for estimating horizontal ground motion amplitudes caused by shallow crustal earthquakes occurring in active tectonic environments. The model provides predictive relationships for the orientation‐independent average horizontal component of ground motions. Relationships are provided for peak acceleration, peak velocity, and 5‐percent damped pseudo‐spectral acceleration for spectral periods of 0.01 to 10 seconds. The model represents an update of the relationships developed by Sadigh et. al. (1997) and incorporates improved magnitude and distance scaling forms as well as hanging‐wall effects. Site effects are represented by smooth functions of average shear wave velocity of the upper 30 m ( V S30 ) and sediment depth. The new model predicts median ground motion that is similar to Sadigh et. al. (1997) at short spectral period, but lower ground motions at longer periods. The new model produces slightly lower ground motions in the distance range of 10 to 50 km and larger ground motions at larger distances. The aleatory variability in ground motion amplitude was found to depend upon earthquake magnitude and on the degree of nonlinear soil response, For large magnitude earthquakes, the aleatory variability is larger than found by Sadigh et. al. (1997).

Growing concerns about global motorization and climate change have led to increasing interest in sustainable transportation alternatives such as bikesharing (the shared use of a bicycle fleet). Since 1965, bikesharing has grown across the globe on five continents: Europe, North America, South America, Asia, and Australia. Today, approximately 100 bikesharing programs are operating in an estimated 125 cities, with more than 139,300 bicycles. Bikesharing's evolution is categorized into three generations: (a) white bikes (or free bike systems), (b) coin-deposit systems, and (c) information technology-based systems. In this paper, a fourth generation is proposed: demand-responsive, multimodal systems. A range of existing bikesharing business models (e.g., advertising) and lessons learned are discussed, including (a) bicycle theft and vandalism, (b) bicycle redistribution, (c) information systems (e.g., real-time information), (d) insurance and liability concerns, and (e) prelaunch considerations. Although limited in number, several studies have documented bikesharing's social and environmental benefits, which include reduced auto use, increased bicycle use, and a growing awareness of bikesharing as a daily mobility option. Despite bike-sharing's ongoing growth, obstacles and uncertainty remain: these include future demand, safety, sustainability of business models, limited cycling infrastructure, challenges to integrate with public transportation systems, technology costs, and user convenience (e.g., limited height adjustment on bicycles, lack of cargo space, and exposure to weather). More research is needed for a better understanding of bikesharing's effects, operations, and business models in light of its reported growth and benefits.

A key component of the NGA research project was the development of a strong‐motion database with improved quality and content that could be used for ground‐motion research as well as for engineering practice. Development of the NGA database was executed through the Lifelines program of the PEER Center with contributions from several research organizations and many individuals in the engineering and seismological communities. Currently, the data set consists of 3551 publicly available multi‐component records from 173 shallow crustal earthquakes, ranging in magnitude from 4.2 to 7.9. Each acceleration time series has been corrected and filtered, and pseudo absolute spectral acceleration at multiple damping levels has been computed for each of the 3 components of the acceleration time series. The lowest limit of usable spectral frequency was determined based on the type of filter and the filter corner frequency. For NGA model development, the two horizontal acceleration components were further rotated to form the orientation‐independent measure of horizontal ground motion (GMRotI50). In addition to the ground‐motion parameters, a large and comprehensive list of metadata characterizing the recording conditions of each record was also developed. NGA data have been systematically checked and reviewed by experts and NGA developers.

Despite increasing regulatory attention and literature linking roadside air pollution to health outcomes, studies on near roadway air quality have not yet been well synthesized. We employ data collected from 1978 as reported in 41 roadside monitoring studies, encompassing more than 700 air pollutant concentration measurements, published as of June 2008. Two types of normalization, background and edge-of-road, were applied to the observed concentrations. Local regression models were specified to the concentration-distance relationship and analysis of variance was used to determine the statistical significance of trends. Using an edge-of-road normalization, almost all pollutants decay to background by 115-570 m from the edge of road; using the more standard background normalization, almost all pollutants decay to background by 160-570 m from the edge of road. Differences between the normalization methods arose due to the likely bias inherent in background normalization, since some reported background values tend to underpredict (be lower than) actual background. Changes in pollutant concentrations with increasing distance from the road fell into one of three groups: at least a 50% decrease in peak/edge-of-road concentration by 150 m, followed by consistent but gradual decay toward background (e.g., carbon monoxide, some ultrafine particulate matter number concentrations); consistent decay or change over the entire distance range (e.g., benzene, nitrogen dioxide); or no trend with distance (e.g., particulate matter mass concentrations).

Abstract Bioenergy deployment offers significant potential for climate change mitigation, but also carries considerable risks. In this review, we bring together perspectives of various communities involved in the research and regulation of bioenergy deployment in the context of climate change mitigation: Land‐use and energy experts, land‐use and integrated assessment modelers, human geographers, ecosystem researchers, climate scientists and two different strands of life‐cycle assessment experts. We summarize technological options, outline the state‐of‐the‐art knowledge on various climate effects, provide an update on estimates of technical resource potential and comprehensively identify sustainability effects. Cellulosic feedstocks, increased end‐use efficiency, improved land carbon‐stock management and residue use, and, when fully developed, BECCS appear as the most promising options, depending on development costs, implementation, learning, and risk management. Combined heat and power, efficient biomass cookstoves and small‐scale power generation for rural areas can help to promote energy access and sustainable development, along with reduced emissions. We estimate the sustainable technical potential as up to 100 EJ : high agreement; 100–300 EJ : medium agreement; above 300 EJ : low agreement. Stabilization scenarios indicate that bioenergy may supply from 10 to 245 EJ yr −1 to global primary energy supply by 2050. Models indicate that, if technological and governance preconditions are met, large‐scale deployment (>200 EJ ), together with BECCS , could help to keep global warming below 2° degrees of preindustrial levels; but such high deployment of land‐intensive bioenergy feedstocks could also lead to detrimental climate effects, negatively impact ecosystems, biodiversity and livelihoods. The integration of bioenergy systems into agriculture and forest landscapes can improve land and water use efficiency and help address concerns about environmental impacts. We conclude that the high variability in pathways, uncertainties in technological development and ambiguity in political decision render forecasts on deployment levels and climate effects very difficult. However, uncertainty about projections should not preclude pursuing beneficial bioenergy options.

The NGA‐West2 project is a large multidisciplinary, multi‐year research program on the Next Generation Attenuation (NGA) models for shallow crustal earthquakes in active tectonic regions. The research project has been coordinated by the Pacific Earthquake Engineering Research Center (PEER), with extensive technical interactions among many individuals and organizations. NGA‐West2 addresses several key issues in ground‐motion seismic hazard, including updating the NGA database for a magnitude range of 3.0–7.9; updating NGA ground‐motion prediction equations (GMPEs) for the “average” horizontal component; scaling response spectra for damping values other than 5%; quantifying the effects of directivity and directionality for horizontal ground motion; resolving discrepancies between the NGA and the National Earthquake Hazards Reduction Program (NEHRP) site amplification factors; analysis of epistemic uncertainty for NGA GMPEs; and developing GMPEs for vertical ground motion. This paper presents an overview of the NGA‐West2 research program and its subprojects.

Since the late 1990s, numerous ridematching programmes have integrated the Internet, mobile phones, and social networking into their services. Online ridematching systems are employing a range of new strategies to create “critical mass”: (1) regional and large employer partnerships, (2) financial incentives, (3) social networking to younger populations, and (4) real-time ridematching services that employ “smartphones” and automated ridematching software. Enhanced casual carpooling approaches, which focus on “meeting places”, are also being explored. Today, ridesharing represents approximately 8–11% of the transportation modal share in Canada and the USA, respectively. There are approximately 638 ridematching programmes in North America. Ridesharing's evolution can be categorized into five phases: (1) World War II car-sharing (or carpooling) clubs; (2) major responses to the 1970s energy crises; (3) early organized ridesharing schemes; (4) reliable ridesharing systems; and (5) technology-enabled ridematching. While ridesharing's future growth and direction are uncertain, the next decade is likely to include greater interoperability among services, technology integration, and stronger policy support. In light of growing concerns about climate change, congestion, and oil dependency, more research is needed to better understand ridesharing's impacts on infrastructure, congestion, and energy/emissions.

We apply recent econometric advances to study the distribution of commuters' preferences for speedy and reliable highway travel. Our analysis applies mixed logit to combined revealed and stated preference data on commuter choices of whether to pay a toll for congestion-free express travel. We find that motorists exhibit high values of travel time and reliability, and substantial heterogeneity in those values. We suggest that road pricing policies designed to cater to such varying preferences can improve efficiency and reduce the disparity of welfare impacts compared with recent pricing experiments.

Carsharing has grown considerably in North America during the past decade and has flourished in metropolitan regions across the United States and Canada. The new transportation landscape offers urban residents an alternative to automobility, one without car ownership. As car-sharing has expanded, there has been a growing demand to understand its environmental effects. This paper presents the results of a North American carsharing member survey (N = 6,281). A before-and-after analytical design is established with a focus on carsharing's effects on household vehicle holdings and the aggregate vehicle population. The results show that carsharing members reduce their vehicle holdings to a degree that is statistically significant. The average number of vehicles per household of the sample drops from 0.47 to 0.24. Most of this shift constitutes one-car households becoming carless. The average fuel economy of carsharing vehicles used most often by respondents is 10 mi/gal more efficient than the average vehicle shed by respondents. The median age of vehicles shed by carsharing households is 11 years, but the distribution covers a considerable range. An aggregate analysis suggests that carsharing has taken between 90,000 and 130,000 vehicles off the road. This equates to 9 to 13 vehicles (including shed autos and postponed auto purchases) taken off the road for each carsharing vehicle.

The “Next Generation of Ground‐Motion Attenuation Models” (NGA) project is a multidisciplinary research program coordinated by the Lifelines Program of the Pacific Earthquake Engineering Research Center (PEER), in partnership with the U.S. Geological Survey and the Southern California Earthquake Center. The objective of the project is to develop new ground‐motion prediction relations through a comprehensive and highly interactive research program. Five sets of ground‐motion models were developed by teams working independently but interacting with one another throughout the development process. The development of ground‐motion models was supported by other project components, which included (1) developing an updated and expanded PEER database of recorded ground motions, including supporting information on the strong‐motion record processing, earthquake sources, travel path, and recording station site conditions; (2) conducting supporting research projects to provide guidance on the selected functional forms of the ground‐motion models; and (3) conducting a program of interactions throughout the development process to provide input and reviews from both the scientific research and engineering user communities. An overview of the NGA project components, process, and products is presented in this paper.

"Growing Cooler: The Evidence on Urban Development and Climate Change." Journal of the American Planning Association, 75(1), pp. 95–96

This paper evaluates and compares strategies for routing a manual picker through a simple warehouse. It expands on previous work, in which optimization algorithms were developed, by deriving equations which relate route length to warehouse attributes. Several rules of thumb are derived for selection of order picking strategies and optimization of warehouse shape.

The data sets, model parameterizations, and results from the five NGA models for shallow crustal earthquakes in active tectonic regions are compared. A key difference in the data sets is the inclusion or exclusion of aftershocks. A comparison of the median spectral values for strike‐slip earthquakes shows that they are within a factor of 1.5 for magnitudes between 6.0 and 7.0 for distances less than 100 km . The differences increase to a factor of 2 for M5 and M8 earthquakes, for buried ruptures, and for distances greater than 100 km . For soil sites, the differences in the modeling of soil/sediment depth effects increase the range in the median long‐period spectral values for M7 strike‐slip earthquakes to a factor of 3. The five models have similar standard deviations for M6.5‐M7.5 earthquakes for rock sites and for soil sites at distances greater than 50 km . Differences in the standard deviations of up to 0.2 natural log units for moderate magnitudes at all distances and for large magnitudes at short distances result from the treatment of the magnitude dependence and the effects of nonlinear site response on the standard deviation.

Carsharing (or short-term auto use) provides a flexible alternative that meets diverse transportation needs across the globe while reducing the negative impacts of private vehicle ownership. Although carsharing appeared in Europe between the 1940s and 1980s, the concept did not become popularized until the early 1990s. For nearly 20 years, worldwide participation in carsharing has been growing. Today, carsharing operates in approximately 600 cities around the world, in 18 nations and on 4 continents. Approximately 348,000 individuals share nearly 11,700 vehicles as part of organized carsharing services (>60% in Europe). Malaysia is operating a carsharing pilot, with a planned launch in 2007. Another eight countries are exploring carsharing. Thirty-three carsharing expert surveys were identified on an international basis. Cost savings, convenient locations, and guaranteed parking were identified as the most common motivations for carsharing use worldwide. An international comparison of carsharing operations, including similarities and differences, is provided. Continued growth is forecast, particularly among new and emerging market segments, such as businesses and universities. Growth-oriented operators will continue to account for the largest number of members and fleets deployed worldwide. In addition, high energy costs; limited and expensive parking; ongoing diffusion of operational knowledge, benefits, and supportive technologies; and increased demand for personal vehicle access in developing nations will affect carsharing's growth and expansion.

Relative contributions by the coarser and finer grains in a silty sand to its stress–strain response are affected by the intergranular matrix structure. The nature of this contribution is illustrated using an intergranular matrix phase diagram in terms of void ratio (e), fines content (FC), and intergranular and interfine void ratios (e s and e f ). New intergranular state parameters (ψ s , ψ f ) and (e s , e f ) are introduced as state variables to characterize silty sands; e s and e f dictate the steady-state characteristics of silty sand at low and high fines contents, respectively; ψ s and ψ f reflect the plastic compressibility characteristics at low and high fines contents, respectively. Using these state variables, the anticipated stress–strain–strength behaviour of silty sand in comparison to that of the host sand is presented. Similar stress-strain behaviour is expected at the same e s and initial confining stress σ′ c , with a few exceptions. At a constant void ratio e, e s increases while e f decreases with addition of fines; a silty sand passes through different states. First, at low fines content, e s (< e max,HS , the maximum void ratio of the host sand, case 1), and high e f the stress–strain behaviour is primarily governed by intergranular friction between the coarser grains. The steady-state line (SSL) is primarily dependent on e s and is fairly independent of σ′ c ; When compared at the same e s and at the same σ′ c (or at the same ψ or ψ s ), the silty sand and the host sand show similar (not identical) stress–strain behaviour; with addition of fines, as e s increases, the collapse potential increases and the stress–strain response becomes weaker. Second, with further addition of fines, when e s approaches or exceeds e max,HS , the SSL is influenced by e s and σ′ c . When e s is near e max,HS (case 2), the stress–strain curves for silty sands are similar at the same e s and the same σ′ c (or at the same ψ or ψ s ), but different from and stronger than that of the host sand. At very loose states (e s > e max,HS ; case 3), the stress–strain curves, normalized with respect to σ′ c , are similar at the same e s (or at the same ψ or ψ s ). Third, with further addition of fines beyond a threshold value, e f becomes sufficiently low (case 4); the fines impart a significant influence, while the role of intergranular (coarser-grain) friction diminishes; the silty sand is expected to behave similarly (not identical) to the host fines at the same e f and ψ f ; at this stage, with further addition of fines, the collapse potential decreases.

To help address the built environmental issues of both heat island and stormwater runoff, strategies that make pavements cooler and permeable have been investigated through measurements and modeling of a set of pavement test sections. The investigation included the hydraulic and thermal performance of the pavements. The permeability results showed that permeable interlocking concrete pavers have the highest permeability (or infiltration rate, ∼0.5 cm s ^−1 ). The two permeable asphalt pavements showed the lowest permeability, but still had an infiltration rate of ∼0.1 cm s ^−1 , which is adequate to drain rainwater without generating surface runoff during most typical rain events in central California. An increase in albedo can significantly reduce the daytime high surface temperature in summer. Permeable pavements under wet conditions could give lower surface temperatures than impermeable pavements. The cooling effect highly depends on the availability of moisture near the surface layer and the evaporation rate. The peak cooling effect of watering for the test sections was approximately 15–35 °C on the pavement surface temperature in the early afternoon during summer in central California. The evaporative cooling effect on the pavement surface temperature at 4:00 pm on the third day (25 h after watering) was still 2–7 °C lower compared to that on the second day, without considering the higher air temperature on the third day. A separate and related simulation study performed by UCPRC showed that full depth permeable pavements, if designed properly, can carry both light-duty traffic and certain heavy-duty vehicles while retaining the runoff volume captured from an average California storm event. These preliminarily results indicated the technical feasibility of combined reflective and permeable pavements for addressing the built environment issues related to both heat island mitigation and stormwater runoff management.

The Pontis bridge management system is the predominant bridge management system employed in the United States. The system employs a network optimization model for preservation, formulated as a Markov decision process with a linear program solution procedure. On each bridge, a set of level-of-service standards determines functional needs, whose benefits are calculated according to a user cost model. A multi-year program simulation generates project alternatives by combining preservation and improvement needs on each bridge. The program is optimized within budget constraints by means of an incremental benefit/cost algorithm.The mathematical formulation of each of these components is presented and discussed. Aspects of system development and data management are outlined, along with the current implementation status. California’s experience with the use of Pontis in its funding process is highlighted.

Dedicated short-range communication (DSRC) and 4G-LTE are two widely used candidate schemes for Connected Vehicle (CV) applications. It is thus of great necessity to compare these two most viable communication standards and clarify which one can meet the requirements of most V2X scenarios with respect to road safety, traffic efficiency, and infotainment. To the best of our knowledge, almost all the existing studies on comparing the feasibility of DRSC or LTE in V2X applications use software-based simulations, which may not represent realistic constraints. In this paper, a Connected Vehicle test-bed is established, which integrates the DSRC roadside units, 4G-LTE cellular communication stations, and vehicular on-board terminals. Three Connected Vehicle application scenarios are set as Collision Avoidance, Traffic Text Message Broadcast, and Multimedia File Download, respectively. A software tool is developed to record GPS positions/velocities of the test vehicles and record certain wireless communication performance indicators. The experiments have been carried out under different conditions. According to our results, 4G-LTE is more preferred for the nonsafety applications, such as traffic information transmission, file download, or Internet accessing, which does not necessarily require the high-speed real-time communication, while for the safety applications, such as Collision Avoidance or electronic traffic sign, DSRC outperforms the 4G-LTE.