NETWORK LOADING VERSUS EQUILIBRIUM ESTIMATION OF THE STOCHASTIC ROUTE CHOICE MODEL MAXIMUM LIKELIHOOD AND LEAST SQUARES REVISITED*

Daganzo (1977, 1979), Daganzo and Sheffi (1977), Sheffi (1985), and Sheffi and Daganzo (1980) have used one assumption about traveler behavior in developing estimation techniques for the stochastic route-choice problem and another assumption in predicting flows on networks by using the same model. In estimation, they calculate the congested travel costs of the network links from observed flows on the network, and the network is loaded based on these costs. In prediction, they follow their stochastic user-equilibrium assumption by which travelers evaluate costs using the mean of the observed flows (or equilibrium flows). The travel-cost coefficient obtained from the loading method systematically overestimates the true travel-cost coefficient from which the observed flow data (which must be used in loading) is generated. The estimates of the same coefficient, obtained in this paper, by constraining the estimation results to conform to the equilibrium conditions are unbiased, and only marginally less efficient (have larger standard deviations). The average percentage error and inefficiency of the link flow predictions based on the loading method increases as the level of congestion on the network rises. In contrast, the average percentage error of link flow predictions based on the equilibrium estimation method declines and their efficiency remains very high as the level of congestion on the network rises.     

Barcelona—fast forward? City entrepreneurialism in the 1980s and 1990s

Since 1979 the city council of Barcelona has sought to guide the city's destiny by a variety of methods, most powerfully by securing the 1992 Olympic Games candidacy, but also by means of two strategic planning exercises, begun in 1988 and 1992. These strategies are examined within their political and economic contexts in order to understand how they relate to changes in Spanish and Catalan politics, in global/local economic shifts and in thinking on city guidance. Significant differences in the three phases of city promotion are identified. It is concluded that strategic planning within the context of the intense spatial economic competition of the late 1990s may be even more difficult for Barcelona than was its drive up to 1992.     

The Pyramids—Cement or Stone?

Several samples of pyramids from Giza were obtained. The samples were analysed by scanning electron microscopy, electron diffraction by X-rays, powder X-ray diffraction, inductively coupled plasmography, Fourier-transform infrared spectroscopy and other techniques. Some scientists who have recently studied the pyramids have suggested that the pyramids were poured into place, stone by stone. The prevailing theory among Egyptologists is, of course, that the pyramids were built from blocks of natural stone. All of the results obtained during this study directly support the concept that the pyramids are made of limestone and are not cementitious in nature.     

Zopilotes,Alacranes, y Hormigas (Vultures,Scorpions, and Ants): Animal Metaphors as Organizational Politics in a Nicaraguan Garbage Crisis

While scholars frequently frame conflicts over urban waste in terms of a politics of infrastructure, this article frames such conflicts in terms of a politics of organization. In 2008, self‐employed recyclers in and around Managua, Nicaragua blockaded local dumps in an effort to secure rights to scavenge for resellable material. Over the course of this “garbage crisis”, a material and semiotic entanglement of human labor organization with animal ecology became politically salient. At different points, recyclers were compared to ants (hormigas), vultures (zopilotes), and scorpions (alacranes). State officials, NGOs, and recyclers themselves used these animal metaphors to describe the organization of waste collection. Drawing on theories of value from political ecology and economic anthropology, as well as analysis of the deployment of these “organic” metaphors, we outline an “organizational politics” of urban waste.