There is a growing interest in transportation pricing reforms (increased fuel taxes, efficient road and parking pricing, and distance-based vehicle insurance and registration fees) to help achieve ...various policy objectives including reduced traffic congestion, accidents and pollution emissions. Their effectiveness is affected by the price sensitivity of vehicle fuel consumption and travel, measured as elasticities (percentage change in consumption caused by a percentage change in price). Lower elasticities imply that price reforms are relatively ineffective in achieving objectives, high prices significantly harm consumers, and rebound effects are small so strategies that increase vehicle fuel efficiency are relatively effective at conserving fuel. Higher elasticities imply that price reforms are relatively effective in achieving objectives, consumers can easily reduce fuel consumption and vehicle travel, and rebound effects are relatively large. Some studies found that US price elasticities declined during the last quarter of the Twentieth Century but recent evidence suggests that vehicle travel has since become more price sensitive. This article examines evidence of changing vehicle fuel and travel elasticities, and discusses policy implications.
► Vehicle travel and fuel consumption appear to be more price sensitive than indicated by many studies performed in the US during the last quarter of the Twentieth Century. ► Pricing reforms are more effective and less harmful to consumers than often assumed, and fuel efficiency regulations provide smaller net benefits due to rebound effects.
Bony fish encode multiple multi-gene families of membrane receptors that are comprised of immunoglobulin (Ig) domains and are predicted to function in innate immunity. One of these families, the ...diverse immunoglobulin (Ig) domain-containing protein (DICP) genes, maps to three chromosomal loci in zebrafish. Most DICPs possess one or two Ig ectodomains and include membrane-bound and secreted forms. Membrane-bound DICPs include putative inhibitory and activating receptors. Recombinant DICP Ig domains bind lipids with varying specificity, a characteristic shared with mammalian CD300 and TREM family members. Numerous DICP transcripts amplified from different lines of zebrafish did not match the zebrafish reference genome sequence suggesting polymorphic and haplotypic variation. The expression of DICPs in three different lines of zebrafish has been characterized employing PCR-based strategies. Certain DICPs exhibit restricted expression in adult tissues whereas others are expressed ubiquitously. Transcripts of a subset of DICPs can be detected during embryonic development suggesting roles in embryonic immunity or other developmental processes. Transcripts representing 11 previously uncharacterized DICP sequences were identified. The assignment of two of these sequences to an unplaced genomic scaffold resulted in the identification of an alternative DICP haplotype that is linked to a MHC class I Z lineage haplotype on zebrafish chromosome 3. The linkage of DICP and MHC class I genes also is observable in the genomes of the related grass carp (
Ctenopharyngodon idellus
) and common carp (
Cyprinus carpio
) suggesting that this is a shared character with the last common Cyprinidae ancestor.
The polymeric immunoglobulin (Ig) receptor (pIgR) is an integral transmembrane glycoprotein that plays an important role in the mammalian immune response by transporting soluble polymeric Igs across ...mucosal epithelial cells. Single pIgR genes, which are expressed in lymphoid organs including mucosal tissues, have been identified in several teleost species. A single
pigr
gene has been identified on zebrafish chromosome 2 along with a large multigene family consisting of 29
pigr
-like (PIGRL) genes. Full-length transcripts from ten different PIGRL genes that encode secreted and putative inhibitory membrane-bound receptors have been characterized. Although PIGRL and
pigr
transcripts are detected in immune tissues, only PIGRL transcripts can be detected in lymphoid and myeloid cells. In contrast to pIgR which binds Igs, certain PIGRL proteins bind phospholipids. PIGRL transcript levels are increased after infection with
Streptococcus iniae
, suggesting a role for PIGRL genes during bacterial challenge. Transcript levels of PIGRL genes are decreased after infection with Snakehead rhabdovirus, suggesting that viral infection may suppress PIGRL function.
Generated traffic has three different impacts to consider in transportation planning and project appraisal: 1. It reduces the congestion-reduction benefit that can result from increased road ...capacity. 2. It often increases external costs, such as downstream congestion, parking demand, uncompensated crash damages and environmental damages. 3. Since it consists of marginal value trips (vehicle travel consumers are most willing to shift or forego if their costs increase), consumer benefits from generated traffic tend to be modest. This article describes how generated traffic occurs, defines different types of generated traffic, discusses their impacts and describes ways to incorporate generated traffic into transport planning and modeling.
In recent years, researchers have developed new methods to measure how transport decisions affect different groups of society. An example is the distribution of impacts (benefits and costs) from ...roadway investments, and the degree that the results are considered equitable (also called fair or just). Such decisions affect people’s ability to access services and activities, and therefore their economic opportunities and development. This study suggests ways of incorporating social equity measures in transportation network planning. It describes various equity impacts that can result from transportation planning decisions, discusses various social equity concepts and theories, reviews previous attempts to incorporate equity considerations into transport networks modeling, and suggests a framework for simultaneously optimizing network design and achieving social equity objectives. According to this framework, network design can be formulated using bi-level integer programming models corresponding to seven major social equity approaches along with the classical approach of “Total Travel Time Minimization.” An accessibility variable is used as the distributable benefit. This approach is more comprehensive and flexible than previous equity impact models. The proposed framework can be used to evaluate and optimize the equity impacts of various infrastructure investment decisions.
Pricing for Traffic Safety Litman, Todd
Transportation research record,
01/2012, Volume:
2318, Issue:
1
Journal Article
Peer reviewed
This paper evaluates the traffic safety impacts of various transport pricing reforms, including fuel-tax increases, efficient road and parking pricing, distance-based insurance and registration fees, ...and public-transit fare reductions. This analysis indicates that such reforms can significantly reduce traffic risk, in addition to providing other important economic, social, and environmental benefits. Crash reductions depend on the type of price change, the portion of vehicle travel affected, and the quality of alternative transport options available. If implemented to the degree justified on the grounds of economic efficiency (for example, to reduce congestion, recover road and parking facility costs, and make insurance more actuarially accurate), these reforms are predicted to reduce North American traffic casualties by 40% to 60%. The low per capita traffic fatality rates in European and wealthy Asian countries result in significant part from their higher transport prices, which result in more efficient multimodal transport systems by which residents drive less and rely more on alternative modes. However, these benefits are often overlooked: pricing reform advocates seldom highlight traffic safety benefits, and traffic safety experts seldom advocate pricing reforms. Taking these steps is particularly important for developing countries now establishing pricing practices that will affect their future travel patterns and therefore crash risks.
The zebrafish (Danio rerio) has become a significant model for understanding the developmental regulation of gene expression and holds considerable potential for characterizing the development of the ...immune system. Using a number of different approaches, including heterologous hybridization and short-primer PCR, cDNAs for three different classes of light-chain genes were identified and characterized. The zebrafish light chains are similar to trout type 1, trout type 2, and catfish type F, respectively. T-cell antigen receptor alpha (TCRalpha) was also identified and characterized. A high proportion of unusual transcripts including sterile transcripts, germline VJC transcripts, aberrant splice forms, and V-V transcripts were encountered in the immunoglobulin and TCR cDNAs examined. The light-chain and TCRalpha loci each consist of multiple families of V gene segments, apparent even from the small numbers of cDNAs of each isotype sequenced. The gene sequences reported provide an essential set of markers of both B- and T-cell lineages that will facilitate investigations of immune system development.
X chromosome-linked agammaglobulinemia is a life-threatening disease that involves a failure in normal development of B lymphocytes and is associated with missense mutations in BTK, a gene encoding a ...cytoplasmic tyrosine kinase (Bruton agammaglobulinemia tyrosine kinase, EC 2.7.1.112), a member of the Tec family of protein-tyrosine kinases. The genomic organization has been determined by using conventional restriction fragment mapping, extended DNA sequencing, and PCR fragment-sizing approaches. The DNA sequences of the 18 coding exons composing BTK and their flanking-region sequences are reported; an additional exon(s) encodes a 5' untranslated segment. Single-base-pair substitutions and 4-nt deletions resulted in amino acid replacement, premature termination, frameshift, and exon deletion in a group of X chromosome-linked agammaglobulinemia patients exhibiting different clinical presentations and courses. The nature of the mutations is interpreted in terms of the genomic organization of the BTK gene and the disease course in individual patients. Several examples are found in which the same mutation occurs in unrelated patients, and one of these mutations occurs at the same codon that is substituted in the murine form of BTK, resulting in X chromosome-linked immunodeficiency disease. Considerable variation in presentation and disease course in X chromosome-linked agammaglobulinemia appears associated with the nature and position of different missense mutations.
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