Monopoly,Subsidies and the Mohring Effect: A Synthesis

Abstract

This paper provides a unifying framework to analyze whether a monopoly transit provider will under or over-supply frequency. To this end we couch the problem in term of Spence [(1975). Monopoly, quality and regulation. The Bell Journal of Economics, 6, 417–429] who analyzed the incentives to provide quality by a monopolist. We show that all of the results of a recent academic exchange discussing this topic are special cases of Spence [(1975). Monopoly, quality and regulation. The Bell Journal of Economics, 6, 417–429], albeit with an adjustment in order to take into account the cost structure of frequency provision in the case of public transport. In theory then, there are cases when a monopolist may offer optimal or above optimal levels of frequency without requiring subsidies. However, public transport is rarely provided by an unregulated monopolist. Rather, these services are usually provided either by an exclusive operator under regulated fares or by a group of competing operators, with or without fare regulation. We show that in the first case frequency will always be below the social optimal level.     

An empirical comparison of travel choice models that capture preferences for compromise alternatives

Compromise alternatives have an intermediate performance on each or most attributes rather than having a poor performance on some attributes and a strong performance on others. The relative popularity of compromise alternatives among decision-makers has been convincingly established in a wide range of decision contexts, while being largely ignored in travel behavior research. We discuss three (travel) choice models that capture a potential preference for compromise alternatives. One approach, which is introduced in this paper, involves the construction of a so-called compromise variable which indicates to what extent (i.e., on how many attributes) a given alternative is a compromise alternative in its choice set. Another approach consists of the recently introduced random regret-model form, where the popularity of compromise alternatives emerges endogenously from the regret minimization-based decision rule. A third approach consists of the contextual concavity model, which is known for favoring compromise alternatives by means of a locally concave utility function. Estimation results on a stated route choice dataset show that, in terms of model fit and predictive ability, the contextual concavity and random regret models appear to perform better than the model that contains an added compromise variable.     

An analysis of soft transport policy measures implemented in Sweden to reduce private car use

Evaluations carried out in many countries show that soft policy measures in the form of personalized travel planning reduce private car use and increase travel by public transport. Sweden is a sparsely populated country that poorly supports public transport, a country with long distances, a cold climate, and a high concentration of private cars, which is why soft policy measures implemented in Sweden may be less cost-effective than has been found in other countries. Thirty-two programs using personalized travel planning were analysed with regard to stewardship, geographic area of application, choice of techniques of exerting an influence, and effects on car use and choice of alternative travel modes. None of the evaluations of the documented programs met the method requirements for such evaluations as regards design and effect measurement. Additionally, reporting was substandard as well as non-standard in the way that is desirable in order to enable comparative analyses. With reservations for these shortcomings, it is inferred that positive effects on a par with the results in other countries have been obtained in some of the implemented programs. It is however necessary to conduct evaluations which are of higher quality. The requirements which will then have to be applied are defined.     

Decision makers and socializers, social networks and the role of individuals as participants

Models explaining and predicting human travel behavior have gone through many changes in the past few decades. As researchers attempt to explain more and predict with more accuracy, the inclusion of social interactions in modeling and simulation is being recognized as a necessity. Among these efforts, researchers have focused on issues such as the composition of social networks, and the constraints and influences that others have on spatial decisions. An important aspect that has been understudied however is the variability or heterogeneity of individuals both as social network members and as participants in these social networks. Understanding the role individuals play in decision-making in different social networks can further define our models to include more accurate representations of human behavior. This research explores the differences between social network composition, and the decision roles members play within different social networks specifically when deciding where to participate in activities. A survey was conducted in Santa Barbara, California on social network involvement, network attributes and decision-making roles within each network. Two separate latent class cluster analysis models were developed to classify social network involvement and roles. Results show that there are clearly different types of social involvement and roles within networks. Further data collection and analysis will be used to better understand how these decision-making roles manifest themselves in activity decision-making.     

Robust control for 4WS vehicles considering a varying tire-road friction coefficient

A µ-synthesis for four-wheel steering (4WS) problems is proposed. Applying this method, model uncertainties can be taken into consideration, and a µ-synthesis robust controller is designed with optimized weighting functions to attenuate the external disturbances. In addition, an optimal controller is designed using the well-known optimal control theory. Two different versions of control laws are considered here. In evaluations of vehicle performance with the robust controller, the proposed controller performs adequately with different maneuvers (i.e., J-turn and Fishhook) and on different road conditions (i.e., icy, wet, and dry). The numerical simulation shows that the designed µ-synthesis robust controller can improve the performance of a closed-loop 4WS vehicle, and this controller has good maneuverability, sufficiently robust stability, and good performance robustness against serious disturbances.     

Effects of mixture stratification on HCCI combustion of DME in a rapid compression and expansion machine

Compression ignition of homogeneous charges in internal combustion (IC) engines is expected to offer high efficiency of DI diesel engines without high levels of NOx and particulate emissions. This study is intended to find ways of extending the rich limit of HCCI operation, one of the problems yet to be overcome. Exhaust emissions characteristics are also explored through analyses of the combustion products. DME fuel, either mixed with air before induction or directly injected into the combustion chamber of a rapid compression and expansion machine, is compressed to ignite under various conditions of compression ratio, equivalence ratio, and injection timing. The characteristics of the resulting combustion and exhaust emissions are discussed in terms of the rate of heat release computed from the measured pressure, and the concentrations of THC, CO, and NOx are measured by FT-IR and CLD. The experimental data to date show that operation without knock is possible with mixtures of higher equivalence ratio when DME is directly injected rather than when it is inducted in the form of a perfectly homogeneous fuel-air mixture. Although fuel injected early in the compression stroke promotes homogeneity of the DME-air mixture in the cylinder, it causes the mixture to ignite too early to secure good thermal efficiency and knock-free operation at high loads. Low temperature reactions occur at about 660K regardless of the fueling methods, fuel injection timing and equivalence ratio. The main components of hydrocarbon emissions turned out to be unburned fuel (DME), formaldehyde and methane.     

Effects of valve timing and intake flow motion control on combustion and time-resolved HC & NOx formation characteristics

In SI engines, valve events have a major influence on volumetric efficiency, fuel economy and exhaust emissions. Moreover, swirl and tumble motions in the intake charge also improve combustion speed and quality by stratifying the mixture as well as intensifying the mixing rate of air and fuel. This paper investigates the behaviors of an engine and the combustion phenomenon for various intake valve timings and intake charge motions using CVVT system and port masking schemes. Test condition includes a part load and a cold idle condition inclusive of a cold start of the engine. Time-resolved HC and NOx emissions were also measured at an exhaust port to examine their formation mechanisms and behaviors with fast response HC/NOx analyzers. In conclusion, the fast burning of fuel and improved combustion quality by enhanced charge motions reduced unburned HC emissions, and advancing the intake valve opening reduced HC as well as NOx. Furthermore, HCs during the cold transient phase and idle conditions decreased with recalibrated start parameters such as lean air-fuel ratio and spark retardation via the enhancement of intake charge motions.     

Fine sediment deposits in shelf seas

From field observations it appears that the top layer of a shelf bottom in general exhibits an intricate geographical pattern of sediment formations. Sediments of different composition are confined in distinct regions. This contradicts the idea that current and wave forces stir up bottom sediment and disperse it in a random way over the shelf; the dispersal process is counteracted by sorting mechanisms. In this paper the bottom patterns of fine cohesive sediments are considered. A specific sorting mechanism is studied which may explain the patchy structure of fine sediment deposits. It is shown that fine sediments can be trapped in bottom deposits which contain a fine sediment fraction high enough to prevent pore water motion in the shelf bed. This mechanism opposes sediment dispersal away from existing deposits. It may also explain the formation or the preservation of mud patches, even in regions where the bottom shear stress is relatively high.     

Thermal exchanges at air-water interfacies and reproduction of temperature vertical profiles in water columns

For a 3-D eutrophication-diffusion macromodel of the central part of the Venice Lagoon, air-water heat fluxes are computed interpolating, through Fourier series expansion, meteoclimatic variables averaged over a thirty years survey. Also reproduced with the same interpolation methods, is the daily fluctuation of incident light as well as the annual variation of the photoperiod.With an interative procedure temperature values, to be assigned at each grid's point and corresponding to each hour of a reference year, are computed also accounting for the thermal inertia of water columns of varying depths. By statistical examination of temperature vertical profiles, depth varying diffusivities are also estimated, which enables, without assumption of an instantaneous mixing, the reproduction of heat diffusion from the surface to the bottom water cells.Procedures, preliminary refined and verified for a one-dimensional vertical system input, are next implemented on a three-dimensional submodel of reduced size provided of “open boundaries”: this last submodel, under a continuous input of energy and of matter is seen to attain a steady states as well as to be capable of simulating regime conditions. A further validation is performed, on a submodel of 43 × 47 × 20 cells, encompassing a limited portion of the macromodel and presenting the actual lagoon bathymetry.Macromodel's seasonalisation so achieved, enables for a more correct simulation of the periodical behaviour of light and of temperature, forcing functions governing the eutrophication phenomena.