bluuebunny/crossref_metadata_2025 huggingface dataset:
Determinants of Within-Patch Microdistribution and Movements of Endangered Butterfly Coenonympha Oedippus (Fabricius, 1787) (Nymphalidae: Satyrinae)
Authors: Čelik Tatjana , Vreš Branko , Seliškar Andrej
Published: January 2010

Determinants of Within-Patch Microdistribution and Movements of Endangered Butterfly Coenonympha Oedippus (Fabricius, 1787) (Nymphalidae: Satyrinae)

The within-patch microdistribution and movements of adults of the critically endangered butterfly, Coenonympha oedippus, were studied using mark-recapture data from an isolated patch network, which consisted of 8 patches in central Slovenia. The impact of patch characteristics on both parameters was analyzed. Males fly longer distances and spend more time flying than females. The distances and seasonal pattern of male movements were dependent on the patch size, and on the microdistribution and density of freshly emerged (receptive) females. The spatial and temporal pattern of female microdistribution was influenced by vegetation height, the homogeneity of host plant stands and the shading of the ground and/or the lowest parts of herb layer. In the case of near continuous distribution of host plants within a patch, the structure of herb vegetation appears to be the major determinant of adult microdistribution. It affects the dynamics of butterfly emergence and the selection of oviposition sites. The per cent cover of the nectar plant, Potentilla erecta, does not play an important role in butterfly microdistribution.
Interglacial complex and solcomplex
Authors: Schirmer Wolfgang
Published: January 2010

All younger Pleistocene interglacials form interglacial complexes. The term interglacial complex is a short term for a tight complex of interglacials, interstadials and breviglacials, separating a complex of warm periods from the long glacial periods (euglacials). In the terrestric environment the interglacial complexes are represented by soil clusters (solcomplexes). Therein which occur interglacial and interstadial soils of different types in the loess environment separated by thin beds of loess or loess derivates (breviglacials). This article considers the mutilation and simulation of solcomplexes. Frequently, fossil solcomplexes present themselves as diminished to a few soils or to one single soil. This mutilation of solcomplexes can be due to soil convergence (soils of different warm periods — interglacials, interstadials — merge to form optically one soil), syn-solcomplex erosion or post-solcomplex erosion and sometimes to soil disguise. Conversely solcomplexes may be simulated by narrowing of soils which belong to different interglacial complexes and moreover by soil divergence (splitting of a soil of one single warm period by an interlayer of rock) or by reworked soil sediment.
The shape of loess particles reviewed
Authors: Howarth John
Published: January 2010

An important property of loess is a tendency to collapse on loading and wetting (hydroconsolidation) which can have serious consequences worldwide for civil engineering projects. This paper describes the use of Monte Carlo and other analytical techniques to predict the shape of naturally occurring loess particles. Randomly generated particles are classified according to Zingg shape categories: disc, sphere, blade and rod. By assuming a uniform distribution for the basic particle, average relative dimensions are calculated for the blade category, into which most loess particles have been shown to fall.
Typological Assessment of Reconstruction: Did Indo-European Have Inclusive and Exclusive First Person Plural Personal Pronouns?
Authors: Shields Kenneth
Published: January 2010

Typological Assessment of Reconstruction: Did Indo-European Have Inclusive and Exclusive First Person Plural Personal Pronouns?

This brief article attempts to apply current typological theory about the structure of person-marking paradigms to reconstructions of early Indo-European personal pronoun declension and early Indo-European verbal conjugation in order to determine whether or not such application can shed light on the traditional debate about whether or not an inclusive/exclusive opposition can be ascribed to the protolanguage. Despite the demonstrated positive value of typology in assessing the plausibility of reconstructions, the conclusion reached here is that current typological theory is very limited in its ability to resolve this particular issue of historical/comparative Indo-European linguistics.
Is the Taxon of Altaic Languages Natural or Artificial?
Authors: Tambovtsev Yuri
Published: January 2010

Is the Taxon of Altaic Languages Natural or Artificial?

The article considers if the taxon of Altaic languages natural enough to call it a good classification. The more compact a taxon, the more natural it is. The article deals with the peculiarities of functioning of labial consonants in the languages of the Altaic language unity and the peculiarities of functioning of labial consonants in subgroups, groups, families and other language taxa of world languages. The analysis is made with the help of such statistical methods as the coefficient of variance, the confidence interval, Chi-square and t-test. The linguistic conclusions on the similarity of functioning of labial consonants are made on the basis of the statistical criteria. It is possible to establish the typological distances between some language taxa (Turkic, Finno-Ugric, Tungus-Manchurian, Slavonic, etc.) on the values of the t-test.
Dagmar S. Wodtko, Britta Irslinger, Carolin Schneider. 2008. Nomina im Indogermanischen Lexikon.
Authors: Blažek Václav
Published: January 2010

Dagmar S. Wodtko, Britta Irslinger, Carolin Schneider. 2008.Nomina im Indogermanischen Lexikon.
Common fetal measurements: A comparison between ultrasound and magnetic resonance imaging
Authors: Parkar Anagha P. , Olsen Øystein E. , Gjelland Knut , Kiserud Torvid , Rosendahl Karen
Published: January 2010

Background: Ultrasound has been the method of choice for antenatal fetal assessment for the past three decades; however, problems may arise in cases of oligohydramnion, unfavorable position of the fetus, and maternal obesity.

Purpose: To compare ultrasound (US) and magnetic resonance imaging (MRI) for common fetal measurements at 19–30 weeks’ gestation, and to assess the effect of high maternal body-mass index (BMI).

Material and Methods: 59 low-risk singleton pregnancies were enrolled in a prospective blinded cross-sectional study. In a first session, an experienced obstetrician used a high-resolution US technique and in a second session on the same day MRI was used to measure biparietal diameter (BPD), head circumference (HC), mean abdominal diameter (MAD), abdominal circumference (AC), and femur length (FL). Inter- and intraobserver and intermodality variability was determined using Bland-Altman plots. The effect of maternal BMI was assessed using Spearman's statistics.

Results: A total of 45 women aged 19–43 years (median 29 years) attended both US and MRI at median 22 weeks’ gestation. The mean differences between US and MRI were 1.6 mm for HC (95% confidence interval [CI] −1.0, 4.3 mm), 1 mm for AC (95% CI −0.2, 4.0 mm), 0.2 mm for MAD (95% CI −0.7, 1.2 mm), 2.2 mm for BPD (95% CI 1.7, 2.7 mm), and 4.6 mm for FL (95% CI 2.9, 6.4 mm). Maternal BMI did not affect the results (Spearman’ rho 0.054–0.277; P=NS). The intraobserver agreement for all MRI measurements was acceptable, except for FL, while the interobserver agreement was poor.

Conclusion: There was good agreement between US and MRI for common fetal measurements, but not for all (i.e., BPD and particularly FL). MRI had a poor interobserver agreement, underscoring the need for technical refinement and reference ranges specifically established for MRI.
Barge Bow Force–Deformation Relationships for Barge–Bridge Collision Analysis
Authors: Consolazio Gary R. , Davidson Michael T. , Cowan David R.
Published: January 2010

The AASHTO specifications pertaining to bridge design for barge collision loads use a static impact force determination procedure. Incorporated within that static procedure is a force–deformation relationship that represents barge bow stiffness. Recently developed dynamic vessel collision analysis techniques, which include mass-related components of bridge response, also require the use of a force–deformation relationship (or crush curve) to model barge bow stiffness. Whether static or dynamic analysis techniques are used, the vessel crush curve largely governs impact forces and, therefore, plays a critical role in quantifying structural response to impact loads. The basis for the AASHTO crush curve is reviewed, and new crush curves are proposed on the basis of finite element crush simulations of multiple high-resolution barge bow models. The barge models developed for this study are based strictly on structural vessel plans obtained from U.S. barge manufacturers and consist of the two most common types of barges traversing U.S. inland waterways (hopper and tanker). Recommended crush curves are then proposed for use in barge–bridge collision analysis and design.
Fatigue Design of Sign Support Structures for Loading Caused by Natural Wind Loads
Authors: Hosch Ian E. , Fouad Fouad H.
Published: January 2010

A unified design method for fatigue loading caused by natural wind for highway overhead sign support structures is needed. Whereas the fatigue design provisions given in the 2001 AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals provide fatigue design criteria for natural wind, these provisions are applicable only within certain limitations. A comprehensive approach was developed for fatigue design for the treatment of sign support structures, considering the dynamic properties of the structures such as the natural frequency and damping characteristics. The approach is applicable for structures in which the dynamic response can be approximated by a single degree-of-freedom system. Typical examples include cantilever-and bridge-type overhead sign support structures. The proposed fatigue design approach incorporates these parameters in a simplified, systematic procedure that can be readily used by the engineer. The analytical work performed involved principles relating to random vibration in use of the vibration response spectrum (VRS). The fatigue load was selected from the VRS in terms of the natural frequency of the structure, the critical damping percentage (a.k.a., damping ratio), and the annual mean wind velocity of the intended site.
Development of a Procedure for Fatigue Design of Slender Support Structures Subjected to Wind-Induced Vibration
Authors: Chang Byungik , Phares Brent M. , Sarkar Partha P. , Wipf Terry J.
Published: January 2010

Cantilevered signal, sign, and light support structures are used nationwide on major Interstate highways, national highways, local highways, and at local intersections for traffic control. Recently, a number of failures of these structures have been characterized as wind-induced fatigue failures. It is widely accepted that there is considerable lack of accuracy in the calculation of wind-induced loads on high mast light poles (HMLPs) in both the AASHTO and the Canadian Highway Bridge Design Code provisions. A coupled model for predicting buffeting- and vortex shedding–induced response for slender support structures was developed. To accomplish this, monitoring of long-term response behavior of an HMLP subjected to wind-induced vibration and wind tunnel experiments was used to study global behavior and to extract important parameters. From the long-term field monitoring and wind tunnel experiments, the two critical types of wind vibration (natural wind gusts or buffeting and vortex shedding) were individually identified for in-depth analysis. Finally, a coupled dynamic model in time domain was developed for predicting the wind-excited response and was validated by comparing the simulation results with the field-collected data. The fatigue life of a specific HMLP was also estimated with the stress amplitudes predicted by the time-domain model and was validated with statistical extrapolation of the field data.
Evaluation of Prestressed Concrete I-Girder Bridge Design Software with NCHRP Process 12-50
Authors: Choe Lisa , Varma Amit H. , Wheeler Eric
Published: January 2010

NCHRP Process 12-50 was used to evaluate and verify prestressed concrete bridge design software commonly used in Indiana. A test bed of 40 bridge structures was developed with input from practicing engineers and Indiana Department of Transportation (INDOT) specialists. The test bed included 20 simple-span and 20 multispan bridges. The primary parameters were bridge span, girder spacing, section type, strand pattern (straight or draped), and concrete strength. The remaining parameters were held constant with practical or consensus values provided by engineers or the INDOT bridge design manual. The section types included were AASHTO Types II, III, and IV and Indiana modified Bulb-Tee beams (54–78 in. deep). An indigenous computer program, PURDUE PSBD, was developed to implement the bridge design calculations specified in the AASHTO LRFD Bridge Design Specifications, which are currently endorsed by the INDOT bridge design manual. Both CONSPAN (the most common bridge design software in Indiana) and PURDUE PSBD generated calculation results for the complete test bed of bridges. The output from both computer programs was compared to identify assumptions and discrepancies from the AASHTO LRFD specifications. These comparisons indicated excellent agreement between the results from both programs for ( a) concrete stresses and deflections at service-level loads, ( b) nominal flexural strength, ( c) nominal shear strength, and ( d) initial camber and deflections. The test bed of bridge structures and the PURDUE PSBD program developed in this research are recommended for evaluating and verifying other bridge design software.
Proposal for Concrete Compressive Strength up to 18 ksi (124 MPa) for Bridge Design
Authors: Rizkalla Sami , Zia Paul , Mirmiran Amir , Russell Henry G. , Mast Robert
Published: January 2010

An extensive experimental and analytical research program was undertaken to recommend revisions to extend the applicability of flexural and compression design provisions for reinforced and prestressed concrete members of the AASHTO LRFD Bridge Design Specifications to concrete compressive strengths up to 18 ksi (124 MPa). The recommended provisions are intended to be seamless and unified over the full range of concrete strengths. The experimental program included tests of material properties; flexural, axial compression, and combined axial and flexure tests of reinforced concrete members; and flexural tests of prestressed concrete members. From the measured test results and the analytical study came several recommendations to revise the specifications; these include modulus of elasticity, modulus of rupture, creep and shrinkage, rectangular stress block parameters for flexural design, minimum area of prestressed, and nonprestressed longitudinal reinforcement for compression members and prestressed girders. The 4-year research program was sponsored by NCHRP and TRB.
Jointless Bridge Deck with Link Slabs
Authors: Ulku Evren , Attanayake Upul , Aktan Haluk
Published: January 2010

Link slabs are used over the piers developing jointless decks while adjacent bridge spans remain simply supported. The Michigan Department of Transportation incorporates link slabs during deck replacements and deep resurfacing. Field performance assessment documented full-depth cracking of most of the link slabs. These cracks allow surface water infiltration, which leads to accelerated deterioration. This study was conducted to address link slab design and performance issues. The literature is inconsistent with the influence of design parameters on link slab performance. The objective was to document the link slab behavior of its design parameters, to propose a method to calculate the link slab moment and axial force, and to propose recommendations for updating current design details and construction procedures. Single-girder, two-span, finite element assemblage models under various types and levels of loads in conjunction with the link slab design parameters were used to evaluate the moments and axial forces developed in the link slab. Analysis showed that support conditions underneath the link slab greatly influence the link slab moment and axial force. Use of moment interaction diagram is recommended for the design. A detailed analysis and design example is presented incorporating live load, temperature gradient load, and the support configurations.
Impact Factors of Curved Steel Multibox Girder Bridges
Authors: Huang Dongzhou
Published: January 2010

A method for estimating dynamic loading of steel multibox girder bridges caused by moving vehicles, based on an extensive parameter analysis of 216 multibox girder bridges, was developed. The curved multibox girder bridge is modeled as a curved grillage system. The analytical vehicle, simulated as a nonlinear vehicle model with 11 degrees of freedom, is the HL-93 truck, as described in the AASHTO specifications. Truck parameters include the body, suspensions, and tires. The bridge deck surface is assumed to be classed as good and is simulated with a stochastic process (power spectral density function). The bridge–vehicle interaction model is validated by field test results from two curved steel box bridges. The analytical results show that the torsion impact factors for curved box girder bridges can be relatively high, whereas moment, shear, and deflection impact factors are normally less than those of corresponding straight box girder bridges because of restricted vehicle speed on curved bridges. The proposed simplified impact equations are appropriate for the design of curved steel box girder bridges.
Probabilistic Structural Health Monitoring Method Applied to the Bridge Health Monitoring Benchmark Problem
Authors: Scianna Adam M. , Christenson Richard
Published: January 2010

A probabilistic structural health monitoring (SHM) method was identified to detect global damage in a highway bridge while accounting for the variability associated in calculating the desired damage measure. The proposed vibration-based monitoring method is applied to the bridge health monitoring benchmark problem. The benchmark structure is a scaled laboratory model of a typical highway bridge. The associated finite element model of this structure is excited with a simulated traffic excitation. The proposed SHM method is intended to meet the practical requirements of using a small number of sensors and detection of damage in a global sense. As such, accelerations are measured at a single location on the bridge. The bridge natural frequencies for a healthy state and a variety of damaged states are considered to help quantify and detect the potential damage. The natural frequencies are determined from the peaks in the power spectral density functions of the measured acceleration response. These natural frequencies are observed to be random variables with a normal distribution. The probability that the current natural frequency is greater than the previously measured healthy natural frequency can then be calculated from the assumed probability density functions and is used to predict, in a global sense, whether damage has occurred on the bridge structure. The results of this simulation-based study were used to extend and apply this method to actual highway bridges in Connecticut.
Analysis of a Gasketed Polyvinyl Chloride Pipe Joint
Authors: Balkaya Müge , Moore Ian D.
Published: January 2010

Poor performance of pipe joints can contribute significantly to reduction of the overall performance of pipe systems. The most common problems attributed to joint defects are infiltration, exfiltration, and erosion of the soil surrounding the pipe, which can ultimately produce pipe failure. Thus, modeling of joints in pipelines is a critical issue influencing both the short- and long-term performance of these systems. Although joints may often be the weakest points along the pipe and can have a significant influence on pipe performance, little research has been conducted with regard to joint design. Even joint response to simple loading conditions is largely unknown because of the complexity of interactions between the pipes and the gasket. A three-dimensional, finite element analysis of a Rieber-type rubber-gasketed polyvinyl chloride (PVC) water pipe joint was carried out to investigate the influence of gasket modulus, rubber–PVC friction, insertion length, and joint rotation on the overall performance of the pipe joint system. The numerical analyses were performed with ABAQUS.
Effective Splices for a Carbon Fiber–Reinforced Polymer
Authors: Dawood Mina , Guddati Murthy , Rizkalla Sami
Published: January 2010

Carbon fiber–reinforced polymer (CFRP) materials have been used successfully to strengthen reinforced concrete bridges and structures. Recently, a new high modulus CFRP strengthening system was developed to increase the allowable load carrying capacity and to enhance the serviceability of steel bridges and structures. Because of the relatively high flexural rigidity of the CFRP materials, the length of the CFRP plates that can be transported to the job site is limited. To implement the proposed strengthening system in longer-span steel bridges, adjacent lengths of CFRP must be spliced. To develop an effective splice joint for the proposed strengthening system, an experimental and analytical research program was conducted to study the bond behavior of the CFRP materials. The parameters considered included plate end geometry, splice length, and the possibility of using mechanical anchorage. The analytical study included a finite element analysis to determine the distribution of the stresses within the adhesive layer for different splice configurations. On the basis of the findings, a simplified method was proposed to design lap splice joints with different reversed taper angles and adhesive properties. The research concluded that, with proper detailing, the proposed CFRP system could be effectively used to strengthen steel bridges and structures.
Investigation into the Bond of Glass Fiber–Reinforced Polymer Stay-in-Place Structural Forms to Concrete for Decking Applications
Authors: Honickman Hart , Nelson Mark , Fam Amir
Published: January 2010

Glass fiber–reinforced polymer (GFRP) pultruded sections have great potential as structural stay-in-place forms for bridge components, including deck slabs. The bond behavior between cast-in-place concrete and GFRP forms, a key consideration in this type of structure, was studied. Eight concrete slabs cast on GFRP plates were fabricated and tested in bending to investigate and compare various bond systems and GFRP reinforcement ratios. No steel reinforcement was used. Bond systems included adhesively bonded freshly cast concrete on the plate, coarse aggregates bonded to the plate before concrete casting, and GFRP and steel mechanical shear connectors. Adhesive bonding to fresh concrete was the most efficient method. Generally, this method resulted in higher flexural stiffness than mechanically connected systems because no slip occurred in the former, whereas progressive slip occurred in the latter from the onset of concrete cracking. Bond failure eventually occurred within a thin layer of cement mortar that remained adhered to the plate. The hybrid slabs were equivalent in strength and stiffness to conventional steel-reinforced slabs of high reinforcement ratios. In addition, the hybrids had the advantage of simple and quick constructability as well as not being hindered by the limitations of concrete cover or rebar spacing. A general analytical model was developed to predict the full behavior and strength of the slabs and was successfully validated. The model can detect various failure modes, including GFRP plate debonding.
Improvement in Fiber-Reinforced Polymer–Concrete Bond by External Pressure
Authors: Aguilar Julio , Winters Danny , Sen Rajan , Mullins Gray , Stokes Mike
Published: January 2010

An experimental study evaluated the improvement in the bond of fiber-reinforced polymer (FRP) and concrete to dry and wet substrates from applied pressure. In the study, 12 full-sized pile specimens, including four controls, were wrapped by using two different glass FRP systems–- a prepreg and a wet layup–-and two different layouts typically used for unidirectional and bidirectional fibers. Wrapping was conducted inside a partially filled tank to ensure that the bonded areas of the dry and wet regions were identical. Sustained pressure was maintained during curing by using pressure or vacuum bagging. Bond improvement was evaluated from more than 400 pull out tests. Results showed that external pressure led to improved bond in both the dry and submerged regions. However, vacuum bagging was better for prepreg systems, whereas pressure bagging was better for wet layups. Transverse fiber layout typically used with bidirectional fibers gave better bond in controls where no external pressure was applied.
Sustained Loading and Temperature Response of Fiber-Reinforced Polymer–Concrete Bond
Authors: Gullapalli Anusha , Lee Jae Ha , Lopez Maria M. , Bakis Charles E.
Published: January 2010

One aspect of long-term behavior of the bond of fiber-reinforced polymer (FRP) and concrete bond has received relatively little attention in the literature: bond stress redistribution and remaining (residual) pulloff strength after sustained loading. The relevance of this missing information is directly related to the expected reliability of FRP-strengthened structures when subjected to sustained loading and elevated temperatures over their life span. The objective of this investigation was to evaluate the effects of sustained loading and temperature on the time-dependent distribution of strain in carbon FRP bonded to concrete and on the pulloff strength of the carbon FRP at room temperature after the sustained loading period. Pulloff specimens were used to evaluate stress distributions during sustained loading tests at loads below ultimate and during tests to ultimate after sustained loading. Under sustained loading, the presence of temperature and a bond-line flaw increased the bond stress transfer length between the FRP and the concrete substrate. However, although the presence of higher temperatures resulted in increased pulloff strength, this beneficial effect was eliminated in the presence of sustained loading.
Exploring Variation Properties of Departure Time Choice Behavior by Using Multilevel Analysis Approach
Authors: Chikaraishi Makoto , Fujiwara Akimasa , Zhang Junyi , Axhausen Kay W.
Published: January 2010

The variation properties of departure time choice behavior are examined by activity type with the use of a continuous 6-week travel survey collected in the cities of Karlsruhe and Halle, Germany, in 1999. The total variation in departure time choice is divided into five variation components: spatial variation, temporal variation at the aggregate level, interhousehold variation, interindividual variation, and intraindividual variation. These variations are first quantitatively analyzed by using a multilevel modeling approach without considering the influences of explanatory variables. Then, on the basis of the clarified variations patterns, how much of the variations can be captured by explanatory variables is examined. It is confirmed that different activities show quite different variations, and of the variations the intraindividual variation accounts for the largest percentage of the total variation. Model estimation results further underscore the need for simultaneously dealing with unobserved macrolevel variations, especially interindividual, interhousehold, and spatial variations, as well as the intraindividual variation, even when the explanatory variables are included in the model. Such quantitative assessment of various types of variations based on a multilevel modeling approach provides a useful guide for the specification of behavior models and deepens the knowledge of behavioral variability by going beyond the traditional paradigm, which focuses on a limited set of variations.
Model for Integrating Home–Work Tour Scheduling with Time-Varying Network Congestion and Marginal Utility Profiles for Home and Work Activities
Authors: Adnan Muhammad , Watling David , Fowkes Tony
Published: January 2010

The existing literature on activity-based modeling emphasizes that individuals schedule their activities by keeping the whole-day activity pattern in mind. Several attempts have been made to integrate this with network congestion; however, for explicit explanation of travel behavior of individuals, further improvements are required. The proposed model is a combined model that addresses the scheduling of the home–work tour with time-varied network congestion in a fixed-point problem framework. Marginal utility profiles that represent individual time-of-day preferences and satiation effect of the activities are incorporated for the measurement of the utility of activity engagement along with the disutility of travel. Consideration of only time-of-day dependent marginal utility profiles of activities in the utility function does not appropriately integrate activities and travel within the tour. The proof is shown analytically and numerically. This finding contradicts earlier research into integration of morning and evening commutes with network congestion. Additionally, the results of two numerical experiments are presented. In the first experiment, an arbitrary dynamic tolling strategy is assumed, and then a detailed analysis is performed to show variation in the balance of trade-offs involved in the process. The second experiment assesses the sensitivity of the combined model through incorporation of different dynamic traffic loading models. Some meaningful observations are drawn from these experiments and are discussed with the identification of avenues for future research.
Fuel Costs, Circulation Taxes, and Car Market Shares
Authors: Vance Colin , Mehlin Markus
Published: January 2010

With efficiency standards and consumer information, car-related taxes are one of three pillars of the European Commission's strategy to reduce CO2 emissions from passenger cars. A long-standing question concerns the effectiveness of such taxes in determining the car-purchasing behavior of households. Several recent studies suggest that purchases are primarily determined by retail cost rather than by taxes, which typically are incurred over the lifetime of the car. Panel data on new car registrations in Germany, Europe's largest car market, were used to address this issue through an econometric analysis of the impact of fuel costs and circulation taxes on car market shares. By using a nested logit model that explicitly recognizes the segmented structure of the car market, the analysis considers correlation in unobserved shocks in cars belonging to the same market segment. Moreover, given the panel structure of the data, a fixed-effects estimator is used to control for the influence of unobservable, time-invariant automobile attributes that could otherwise induce biases in the estimated coefficients. Contrasting with much of the evidence garnered to date, the results suggest that circulation taxes and fuel costs significantly determine car market shares and hence may serve as effective instruments in influencing the composition of the car fleet and associated CO2 emissions.
Travel, Activities, and Money
Authors: Ettema Dick
Published: January 2010

Although microeconomic models of the trade-off between time and money expenditures exist, these have been applied primarily in theoretical or simplified empirical settings. Yet, studying how time and money are traded off against each other in the context of daily activity patterns is crucial because of relationships that exist between activities and between various dimensions of one activity and because of increasing importance of the quality of places and facilities. To facilitate the analysis of expenditures, a theoretical framework was developed; it suggests that money can be invested directly into activities and indirectly into the facilities that support the activities (dwellings, transport, telecommunication devices). Focusing on the trade-off between various types of fixed expenditures (related to facilities) and daily expenditures, an exploratory analysis was carried out by using a 1996 Dutch data set. The analysis revealed that expenditure decisions are influenced by such factors as education level, age, frequency of social interactions, nationality, presence of children, and monthly income. In addition, a substitution effect is found between daily expenditures and expenditures to the dwelling, transport, and telecommunication.
Effects of Physical Activity on Propensity for Sustainable Trips
Authors: Meloni Italo , Portoghese Alessandro , Bez Massimiliano , Spissu Erika
Published: January 2010

Recent statistics about the low level of participation by individuals in physical activities as well as a generalized propensity to use private vehicles have broadened the scope of transport studies to the sphere of health and well-being. The current shift in travel demand modeling to the activity-based paradigm is central to investigating which population segment is more likely to opt for environmentally friendly and energy-efficient vehicles, alternative modes of transport, and a rational use of the motor car. A mixed, joint Tobit–probit model analyzes the effects of time allocation for daily activity on the propensity to sustainable trips. The model is applied to a sample of workers and students age 14 and older, drawn from a time-use survey conducted in Turin, Italy, and its metropolitan area. The analysis suggests the presence of self-selection effects between active lifestyles and sustainable mandatory trips. The model predictions highlight the substantial contribution of transportation interventions in getting individuals to engage in healthier behaviors.
Comprehensive Model of Worker Nonwork-Activity Time Use and Timing Behavior
Authors: Rajagopalan Bharath S. , Pinjari Abdul Rawoof , Bhat Chandra R.
Published: January 2010

A comprehensive, high-resolution model for out-of-home nonwork-activity generation is developed; it considers daily activity time-use behavior and activity timing preferences in a unified random utility framework. The empirical analysis is undertaken with data from the 2000 San Francisco, California, Bay Area Travel Survey. Several important household and commuter demographics, commute characteristics, and activity travel environment attributes are found to be significant determinants of workers’ nonwork-activity time use and timing behavior. The developed comprehensive model can serve as an activity-generation module in an activity-based travel demand microsimulation framework.
Who are Bicyclists? Why and how much are they Bicycling?
Authors: Sener Ipek N. , Eluru Naveen , Bhat Chandra R.
Published: January 2010

The factors influencing the decision to bicycle are explored and unraveled to inform the development of appropriate and effective strategies to increase bicycling and promote the health of individuals and of the environment. The data used in the analysis were drawn from a survey of Texas bicyclists, and the study includes a comprehensive explanatory analysis of bicyclists and their bicycling habits. Various econometric models are used to evaluate the determinants of bicyclists’ perception for safety and quality issues and the frequency of bicycling for commute and noncommute purposes. The results of the study indicate that the perceptions of the quality of bicycle facilities and safety from traffic crashes show significant variation depending on bicyclists’ demographic and work characteristics and bicycle amenities and facilities on the commute route and at the workplace. Bicyclist demographics (gender, age, education level, commute distance), household demographics (number of automobiles, number of bicycles, number of children), residential location and season, bicycle amenities at work (bicycle racks, showers), bicyclist perceptions of the overall quality of bicycle facilities, and bicycle-use characteristics affect commute and noncommute bicycling frequency. These study results can assist in the development of informed policies to increase commute and noncommute bicycling, and the results highlight the ongoing need for detailed surveys to understand bicycling behavior.
Intrahousehold Interaction in Transit-Oriented Residential Choice Behavior Represented in Stated Preference Approach
Authors: Zhang Junyi , Fujiwara Akimasa
Published: January 2010

A study applied a web-based stated preference (SP) survey to investigate household preferences for transit-oriented residential choices, incorporating intrahousehold interaction. The SP survey included five alternatives: one current residential location and four combinations of two residential areas and two commuting modes (a car and a transit system). The assumed residential areas were all located near stations of a transit system: one was close to and another was far from the city center. Commuting modes were only for household heads. Households with only couples were recruited, and the survey was conducted with the help of an Internet survey company. In the SP survey, the couple was first asked to answer the SP questions separately, and then the two members jointly answered the questions. It was found that members in 40% of the households changed their stated choices after joint decisions. This switch suggests the necessity to incorporate intrahousehold interaction into any household residential choice model. To this end, a group discrete choice model with multilinear utility was established; members’ relative influences and intrahousehold interaction were simultaneously represented in the model. Model estimation results first confirmed the effectiveness of the established model. It was then revealed that the existence of intra-household interaction reduced total household utility and that husbands wielded relatively greater influence than wives. It was also shown that with increases in age, members’ relative influence grew, and that dominant decision makers concerning household asset management had greater influence power on household residential choice behavior.
Investigation of Planning Priority of Joint Activities in Household Activity-Scheduling Process
Authors: Kang Hejun , Scott Darren M. , Doherty Sean T.
Published: January 2010

Operational models of the household activity-scheduling process have emerged recently. These models replicate the sequence of decisions that leads to observed patterns of human activities and travel, including which activities to conduct, with whom, for how long, at what time and location, and by what mode. Activity priority has been suggested as an important dimension in such scheduling models, particularly as a determinant for the choice and sequencing of activities. The importance of intrahousehold interactions, joint activities in particular, has led to a rapid expansion of research on this topic. However, within most scheduling models, joint activities have been addressed, at best, by assuming that they are preplanned relative to independent activities. Within this context, two important issues concerning the planning of joint activities are explored: the extent to which joint activities are preplanned and whether male and female householders share the same priority when scheduling joint activities. The data set used for the study was the 2003 Computerized Household Activity Scheduling Elicitor survey for Toronto, Ontario, Canada, which recorded information about when a particular activity was planned by respondents. In the analysis, bivariate probit models are estimated for two scheduling alternatives (impulsive or preplanned) for husband and wife. Overall, the empirical results highlight the need to move beyond static priority assumptions for determining the sequencing of activities to develop a behaviorally sound model for activity scheduling. Furthermore, differences in planning priority across individual participants should be taken into account.
How Far is Too Far?
Authors: Susilo Yusak O. , Dijst Martin
Published: January 2010

It is widely believed that providing activity locations close to residential locations reduces the travel time of residents. However, it has not been clear how close to one another activity locations and residential locations should be. The Dutch National Travel Survey and a travel time ratio index were used to measure acceptable travel times in relation to duration times of various activities. The results show that the value of an individual travel time ratio depends on the type of activity, individual commitments, available travel mode, and activity locations. Each activity has a unique tradeoff relationship between activity duration and travel time. Each activity also has its own turnover point–-a point at which increased activity duration will lead to less instead of more travel time. The analysis also shows that the travel time ratio value is influenced not only by an individual's activity commitments, resources, and constraints but also by the trade-off within households.
Estimation of Road Traffic Demand Elasticities for Mexico City, Mexico
Authors: Crôtte Amado , Noland Robert B. , Graham Daniel J.
Published: January 2010

A study was done to estimate price, income, vehicle stock, metro fares, and fuel-efficiency elasticities of the demand for road traffic in Mexico City, Mexico. Dynamic panel generalized method of moments (GMM) models are estimated with annual data from the 16 Mexico City boroughs for 2000 to 2004. The results show that the available instruments in both the difference and system GMM specifications are weak and the estimator is biased. The elasticities are therefore estimated with a static within-groups approach. The estimated medium-run traffic elasticity for fuel prices is -0.117, much smaller than the average estimates reported in the literature, a pattern also found for fuel-demand elasticities in Mexico City. These results suggest that a road user charge equivalent to 10% of the price of fuel would reduce traffic by only about 1.2% but would be effective in increasing government revenue. The results also show that road traffic grows in line with economic development, as the combined effect of income and vehicle stock is close to unity. Traffic elasticities for metro fares are negligible, which suggests little substitution between transport modes. Finally, the positive fuel-efficiency elasticity shows that as vehicles become more fuel efficient, road traffic increases, although less than proportionally.
Travel Time Reliability for Stockholm Roadways
Authors: Franklin Joel P. , Karlstrom Anders
Published: January 2010

In recent years, there has been an increasing awareness that travel time reliability, apart from expected travel time, is an important component of cost–benefit analysis, especially during congested traffic conditions. A common measure of travel time reliability is standard deviation, and it has been shown that this is a theoretically sound measure under scheduling constraints, provided that the mean lateness factor is known. Hence, in applied cost–benefit analyses, one will need both the standard deviation and the mean lateness factor. These analyses would be particularly simple if the mean lateness were constant across time of day and for different routes chosen. A study was done to explore how the mean lateness varies and how its variations can be approximated. With the use of travel time measurements on individual links, it is shown how mean lateness varies considerably across time and space. It is shown that mean lateness exhibits a time-varying pattern depending on the characteristics of congestion on the link. It is also shown that the location of the link in the network is a significant determinant. The resulting model for mean lateness represents a considerable improvement over existing practice, where the mean lateness is implicitly assumed constant, yet a large portion of its variation remains unexplained. The model is useful for informing future research but is of less value for predicting the mean lateness in broad applied settings.
Extent to Which Sustainable Travel to Work can be Explained by Neighborhood Design Characteristics
Authors: Aditjandra Paulus T. , Mulley Corinne , Nelson John D.
Published: January 2010

A case study approach is used to present causal evidence from the United Kingdom on the impact of neighborhood design on travel behavior. “Sustainable travel to work” is defined as including walking, cycling, and travel by bus or light rail. Travel-to-work data are derived from the British Census 2001 for two groups of carefully selected neighborhoods–- those exhibiting either a high or a low incidence of sustainable travel-to-work patterns. A questionnaire was used to capture dimensions of neighborhood attitudes and preferences, socioeconomic characteristics, and car-travel characteristics in the northeast of England. The results offer microscale evidence by using a cross-sectional design to investigate the relationship between neighborhood characteristics and travel behavior and by using multivariate analysis to explore differences between neighborhood groups for socioeconomic variables, travel attitudes, and perceived neighborhood characteristics. The neighborhood group with a high incidence of sustainable travel to work is shown to have a higher potential to travel farther, and the neighborhood group with a low incidence of sustainable travel to work is shown to have a higher potential to use public transport. These results imply a policy dilemma about how public preferences for improved travel accessibility should be met by local authorities.
Activity Travel Planning and Rescheduling Behavior
Authors: van Bladel Kelly , Bellemans Tom , Janssens Davy , Wets Geert
Published: January 2010

Travel behavior research of the past few years has shown an increasing interest in dynamic activity scheduling. Research was done to analyze factors influencing the actual activity scheduling process by using detailed activity travel data from an extensive data set collected in Flanders (Belgium). A model examines the attributes that influence activity planning; a second model analyzes the factors that affect activity rescheduling. The explanatory variables considered in both models are individual, household, activity, and schedule attributes, and their impact is analyzed by using mixed logit models. Random effects are added to the models to test for within-individual variance. The results reveal that activity and schedule characteristics considerably affect activity planning. The rescheduling model also has several highly significant activity and schedule attributes. Most individual and household attributes considered do not influence activity planning and rescheduling behavior, although strong statistical evidence indicates that individual-specific preferences for planning and rescheduling determine the process of activity scheduling.