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431.
This paper investigates the role that enhanced service quality introduced into a deregulated market has in improving the experience
of bus travel by a sample of passengers in the Tyne and Wear area of England. A generalised ordered choice (GOC) model that
accounts for preference heterogeneity through random parameters, as well as heteroscedasticity in unobserved variance, and
random parameterisation of thresholds, is implemented to identify sources of influence on the overall experience of bus travel
in the presence and absence of the quality-enhanced treatment of service. The GOC model is contrasted with a standard ordered
logit model, and the marginal effects associated with the preferred GOC model are derived for each influencing attribute,
taking into account the various ways in which each influence contributes to the utility associated with each level of bus
experience. The paper supports a view that the introduction of quality improvements, via a Quality Bus Partnership, does contribute
non-marginally to an increase in a positive bus experience, and signals a way forward through cooperative intervention, to
grow patronage. Knowing which attributes successfully deliver a more positive experience (and those that do not) means that
resources are effectively targeted at the aspect of service provision which will increase patronage and therefore revenues,
satisfying the objectives of both the bus operator and the local authority partner. 相似文献
432.
Daniel J. Mayor Thomas R. Anderson David W. Pond Xabier Irigoien 《Journal of Marine Systems》2009,78(4):511
The egg production of marine copepods correlates with a range of variables, including the availability of organic carbon (C), nitrogen (N) and the polyunsaturated fatty acids (PUFAs) 20:5(n−3) (EPA) and 22:6(n−3) (DHA). However, an understanding of which substrates limit egg production in the natural environment has yet to be reached. The quantities of C, N, EPA and DHA ingested, derived from parental biomass, and invested in eggs by female Calanus finmarchicus during a 5-day incubation experiment were examined using stoichiometric theory to determine which substrate was limiting. The majority of each substrate was derived from parental biomass, and therefore the existing stoichiometric theory is developed to include this route of supply. The females were essentially devoid of lipid reserves, as evidenced by the lack of the storage fatty acids 20:1(n−9) and 22:1(n−11), and carbon limitation was predicted under most of the scenarios examined. Nitrogen limitation was only apparent when carbon and nitrogen utilisation efficiencies were assumed to be high (0.5) and low (0.4) respectively. PUFAs were assumed to be utilised with high efficiency (0.9), and were never predicted to limit production. This work highlights the need for a more detailed understanding of the maintenance requirements that marine copepods have for C, N, EPA, and DHA and hence the efficiencies with these substrates can be utilised for growth. 相似文献
433.
David A. Hensher John M. Rose Juan de Dios Ortúzar Luis I. Rizzi 《Transportation Research Part A: Policy and Practice》2009,43(7):692-707
In recent years there has been a re-focus on the valuation of a statistical life from the ex post or human capital method to an ex ante willingness to pay (WTP) approach. This is in part a recognition that we may have been undervaluing the cost of fatalities and injuries to society associated with crashes, but also a strong belief in the need to focus on establishing the amount, ex ante, that individuals are willing to pay to reduce the risk of exposure to circumstances that might lead to death or degree of injury on the road network. This study has developed a framework in which to identify the degree of preference heterogeneity in willingness to pay by individuals who are drivers or passengers in cars to avoid being killed or injured. A stated choice experiment approach is developed. The empirical setting is a choice of route for a particular trip that a sample of individuals periodically undertakes in Australia. The particular trip is described in enough detail to provide the respondent with a familiar market environment, providing all the relevant background information required for making a decision. Mixed logit models are estimated to obtain the marginal (dis)utilities associated with each influence on the choice amongst the attribute packages offered in the stated choice scenarios. These estimates are used to obtain the WTP distributions for fatality and injury avoidance, which are then aggregated to obtain estimates of the value of risk reduction (VRR), of which the fatality class is also known as the value of a statistical life (VSL). 相似文献
434.
The seaborne oil transportation market is served by two main types of vessels—crude oil tankers and product tankers. Product tankers are designed to move refined oil products, yet they can also opportunistically carry ‘dirty’ products such as crude and heavy fuel oil, subject to the cost of tank cleaning when re-entering the clean products trade. We apply an entry-exit real option model with a stochastic freight rate differential to derive optimal triggers for switching between the two cargo types and estimate the value of the switching option. We show that the value of active switching has grown over time, and generally exceeds the additional construction cost of a product tanker. Our findings are important both from a practical point of view and for our understanding of market integration in the tanker freight market. Specifically, shipowners can use our model as a basis for optimizing chartering policy for clean product tankers. We also show that there are periods where the dirty market is persistently stronger, and discuss the possible reasons for such apparent inefficiencies. 相似文献