Rational behaviour, Risk aversion, High stakes for society

Certain areas related to the topics under discussion here lie outside my field; for instance the evaluation of risk assessment and security deficiencies in the transport sector. What has convinced me of the importance of this subject are a few very general conclusions, indeed I would say, impressions, that I have drawn from the truly remarkable development of our powers to analyse the risk decision-making process over some years now.Risk, uncertainty, home security, expected utility, non-expected utility, OECD

Transition choice probabilities and welfare analysis in random utility models

We study the descriptive and the normative consequences of attribute changes in standard discrete choice models. For additive random utility models, we derive expressions for the transition choice probabilities for a change in the systematic utility. We then use these expressions to compute the CDF’s of the compensating variation conditional on the initial and on the final choices. The conditional moments of the compensating variation are obtained as a one-dimensional integral of the transition choice probabilities. We also provide a stochastic version of Shephard’s Lemma when transitions are observed. Example of the logit and the disaggregated CES are also studied.Random Utility Models, Transition Choice Probabilities, Multinomial Logit Model, CES, Conditional Compensating Variation, Shephard’s Lemma.

Traffic Congestion Pricing Methods and Technologies

This paper reviews the methods and technologies for congestion pricing of roads. Congestion tolls can be implemented at scales ranging from individual lanes on single links to national road networks. Tolls can be differentiated by time of day, road type and vehicle characteristics, and even set in real time according to current traffic conditions. Conventional toll booths have largely given way to electronic toll collection technologies. The main technology categories are roadside-only systems employing digital photography, tag and beacon systems that use short-range microwave technology, and in vehicle-only systems based on either satellite or cellular network communications. The best technology choice depends on the application. The rate at which congestion pricing is implemented, and its ultimate scope, will depend on what technology is used and on what other functions and services it can perform. Since congestion pricing calls for the greatest overall degree of toll differentiation, congestion pricing is likely to drive the technology choice.Road pricing; Congestion pricing; Electronic Toll Collection technology

Dynamic and Static congestion models: A review

We begin by providing an overview of the conventional static equilibrium approach. In such model both the flow of trips and congestion delay are assumed to be constant. A drawback of the static model is that the time interval during which travel occurs is not specified so that the model cannot describe changes in the duration of congestion that result from changes in demand or capacity. This limitation is overcome in the Vickrey/Arnott, de Palma Lindsey bottleneck model, which combines congestion in the form of queuing behind a bottleneck with users' trip-timing preferences and departure time decisions. We derive the user equilibrium and social optimum for the basic bottleneck model, and explain how the optimum can be decentralized using a time-varying toll. They then review some extensions of the basic model that encompass elastic demand, user heterogeneity, stochastic demand and capacity and small networks. We conclude by identifying some unresolved modelling issues that apply not only to the bottleneck model but to trip-timing preferences and congestion dynamics in general

Congestion on risky routes with risk adverse drivers

We study the impact of information on risk adverse drivers who maximize their von Neumann and Morgerstern expected utility (rather than minimizing expected travel time). The preferences of the users are described by their utility functions. Beside the (potentially inconsistent) mean variance model used so far in transportation, we consider three other standard utility functions: the mean standard deviation model, and the CARA and CRRA utility functions. We show that maximization of expected utility provides a more general formulation than minimization of expected travel time (the latter case corresponds to the standard Wardrop principle). We illustrate the proposed approach with a simple network which consists in one origin/one destination and two routes in parallel. Total demand is inelastic. Capacity on one route is constant and on the other route it is stochastic, and depends on the states of nature, with two possible values. We assume that all users have the same value of time but that they differ in their risk aversion parameter. Equilibrium travel time then depends on the distribution of risk aversion. We consider two polar information regimes: no information and full information. We study the differential impacts of information according to the level of risk aversion, and compute the social value of information. We introduce a formula to compute the value of information that is the individual willingness to pay for information (or in economic terms, the compensating variation). Moreover, we find that optimal route choice may depend on global factors (and not only on local traffic conditions). This has serious implications on the design of driver information systems. Finally, we study road pricing when users are risk neutral (and minimize the expected travel time) and when users are risk adverse. We compare the level of tolls, as well as the benefits of road pricing with and without taking into account risk aversion.

Transition choice probabilities and welfare in ARUM's

We study the descriptive and the normative consequences of price and/or other attributes changes in additive random utility models. We first derive expressions for the transition choice probabilities associated to these changes. A closed-form formula is obtained for the logit. We then use these expressions to compute the cumulative distribution functions of the compensating variation conditional on ex-ante and/or ex-post choices. The unconditional distribution is also provided. The conditional moments of the compensating variation are obtained as a one-dimensional integral of the transition choice probabilities. This framework allows us to derive a stochastic version of Shephard's lemma, which relates the expected conditional compensating variation and the transition choice probabilities. We compute the compensating variation for a simple binary linear in income choice model and show that the information on the transitions leads to better estimates of the compensating variation than those obtained when only ex-ante or ex-post information on individual choices is observed. For the additive in income logit, we compute the conditional distribution of compensating variation, which generalizes the logsum formula. Finally, we derive a new welfare formula for the disaggregated version of the represen- tative consumer CES model.Additive random utility models (ARUM), Logit, Transition choice probabilities, Compensating variation, Shephard's Lemma, Logsum, CES

The influence of information availability on the choice of destination

We set a framework where an individual has to choose one among a set of spatially distributed activities. The individual knows the price of each activity, as well as the distance to reach it. She has either full or zero information about each activity's quality. Qualities are modeled by i.i.d. random variables. Under the full information regime, the individual knows the realizations of the qualities; while under the no information regime, she only knows the distribution of the qualities. In that case, she can decide either ex ante, or en route, how many activities to patronize. We analyze the impact of information availability on the choice process, on the distance the individual covers, and on the individual's expected utility. In this framework, more information yields longer distance traveled, but also higher utility. We compute the individual's willingness to pay for information. Finally, we show that providing information may decrease the individual's benefit when congestion arises.travel demand, search, logit, information regimes, value of information, differentiation

MARKET PERFORMANCE WITH MULTIPRODUCT FIRMS

We revisit the fundamental issue of market provision of variety associated with Chamberlin, Spence, and Dixit and Stiglitz when firms sell several products. Both products and firms are envisaged as di?erentiated. We propose a nested demand model where consumers decide upon a firm then which variant to buy, and use it to determine the market’s biases when firms compete in product ranges and prices. The market system attracts too many firms with too few products per firm: firms restrain product ranges to relax price competition, but this exacerbates overentry. The results extend to generalized nested CES models.Multiproduct firms, excess variety, nested demand, product line competition

Information Congestion: open access in a two-sided market

Advertising messages compete for scarce attention. “Junk” mail, “spam” e-mail, and telemarketing calls need both parties to exert effort to generate transactions. Message recipients supply attention depending on average message benefit, while senders are motivated by profits. Costlier message transmission may improve message quality so more messages are examined. Too many messages may be sent, or the wrong ones. A Do-Not-Call policy beats a ban, but too many individuals opt out. A monopoly gatekeeper performs better than personal access pricing if nuisance costs to receivers are moderate.information overload, congestion, advertising, common property resource, two-sided markets, junk mail, email, telemarketing, Do Not Call List, message pricing policy.

Information Congestion

Advertising messages compete for scarce attention. ?Junk? mail, ?spam? e-mail, and telemarketing calls need both parties to exert effort to generate transactions. Message recipients supply attention depending on average message beneÞt. Senders are motivated by proÞts. Costlier message transmission may improve message quality so more messages are examined. Too many messages may be sent, or the wrong ones. A Do-Not-Call policy beats a ban, but too many individuals opt out. A monopoly gatekeeper performs better than personal access pricing if nuisance costs are moderate. The medium is the message with multiple channels, and there is excessive indiscriminate mailing.information overload, congestion, advertising, common property resource, overÞshing, two-sided markets, junk mail, email, telemarketing, Do Not Call List, message pricing, the Medium is the Message, market research.