The economics of airport congestion pricing

Conventional economic wisdom suggests that congestion pricing would be an appropriate response to cope with the growing congestion levels currently experienced at many airports. Several characteristics of aviation markets, however, may make naive congestion prices equal to the value of marginal travel delays a non-optimal response. This paper develops a model of airport pricing that captures a number of these features. The model in particular reflects that (1) airlines typically have market power and are engaged in oligopolistic competition at different sub-markets; (2) part of external travel delays that aircraft impose are internal to an operator and hence should not be accounted for in congestion tolls; and (3) different airports in an international network will typically not be regulated by the same authority. We present an analytical treatment for a simple two-node network and some numerical results to illustrate our findings. Some main conclusions are that second-best optimal tolls are typically lower than what would be suggested by congestion costs alone and may even be negative, and that cooperation between regulators need not be stable but that non-cooperation may lead to welfare losses also when compared to a no-tolling situation. © 2003 Elsevier Inc. All rights reserved

Natural cytotoxic macrophages in the peritoneal cavity of mice.

Many strains of mice from various breeding institutes have natural cytotoxic macrophages. These macrophages can also be present in nude mice, suggesting that this cytotoxicity can be acquired without invovlvement of T cells. The natural cytotoxicity was non-specific for tumour cells, was not sensitive to trypsin treatment, was lost after 5 days incubation, but could be enhanced by foetal bovine serum. The presence of cytotoxic macrophages in the peritoneal cavity was not genetically or age controlled. Natural cytotoxic macrophages did not occur in germ-free mice. The possible causes of natural cytotoxicity are discussed

Choice of departure station by railway users

This paper applies a multinomial logit model to the choice of a departure railway station by Dutch railway passengers. This is a relevant theme since about 50% of Dutch railway passengers do not travel via the nearest railway station. The passengers’ choices for departure stations are aggregated at the four digit postal code area level. We applied three functional forms for the underlying systematic utility of a station, namely a linear effect of attributes, cross effect of distance and frequency of service, and a translog formulation on distance and frequency of train services. With 3,498 post code areas and 360 railway stations our analysis found consistent effect sizes for distance, frequency of service, intercity status of the station and the presence of park-and-ride facility on the choice of departure station. The effect of distance on the choice of a departure station declines smoothly. The effect of frequency of service is relatively small compared to the effect of distance. A frequency of service increase by a hundred trains per day is equivalent to being 600 m closer to the station. The Intercity status of the station plays the biggest role in the choice of departure station. It has an equivalent effect of a change in 2 km distance or about a frequency of service of 300 trains per day. In addition, the presence of park-and-ride facility in the station poses a sizable effect in the departure station choice. In most cases its effect reaches about 35% of the intercity status effect