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.     

WHY ARE URBAN TRAVEL TIMES SO STABLE?

Personal travel time in U.S. urban areas has been stable, clashing with the assertion that urban sprawl greatly lengthens travel. Average commute time rises by 7.7 percent with each cross‐sectional doubling of Metropolitan Statistical Area (MSA) jobs. Using the RELU‐TRAN structural computable general equilibrium model of the Chicago MSA, we simulate the equilibrium effects of a 24 percent population increase projected from 2000 to 2030 by the Chicago Metropolitan Agency for Planning. If no new road capacity is added, then congestion per mile increases. Although the urbanized land area increases by 19 percent, indicating sprawl, the vehicle miles traveled (VMT) per car‐trip decreases by 1.31 percent and the VMT per car‐trip to work decreases by 2.78 percent. Car travel time increases by only 6.25 percent and commuting time by only 4.54 percent, from 30.3 minutes in 2000 to 31.7 in 2030 or 3.4 seconds per year. We further explore the effects of new road capacity, gasoline prices, public transit speed, fuel economy gains, limits on suburban construction, and importantly, the cross‐elasticity of public transit use with respect to car times. The availability of public transportation, economizing on nonwork travel, and land use adjustments that increase job‐residence proximity keep times stable.     

Dendrochronological methods for reconstructing mass movements — An example of landslide activity analysis using tree-ring eccentricity

Dendrochronological methods can be applied to the reconstruction of different types of environmental events such as climate changes, fires, glacier movements, floods, earthquakes, volcano activity. In the field of geomorphology dendrochronology is increasingly frequently used for the absolute dating of different types of mass-movements (rock falls, landslides and debris flows, etc.). Trees growing on slopes transformed by mass-movements are tilted and wounded while their stems and root systems are exposed or buried under sediment. These events are recorded in wood anatomy as eccentric growth, reaction wood, scar overgrowth by callous tissue, changes in cell size or adventitious root production. Dating changes in wood anatomy allows to date and precisely reconstruct the spatial and temporal occurrence of mass-movements with at least one year resolution. The paper provides a review of existing dendrochronological tools used in geomorphology and also an example of the application of eccentric tree-growth to reconstruct landsliding. Using tree-ring eccentricity allows to (1) obtain a dynamic depiction of slopes, (2) study landslide activity, not only contemporary, but also in the last tens of hundreds of years (depending on the stand age).     

Pious Way to Politics: The Rise of Political Salafism in Post‐Mubarak Egypt

The Arab Spring has reshaped the Islamist landscape in the Middle East drastically. After decades of repression and exclusion, Islamist parties have taken power in Egypt, Tunis, and Morocco. However, the startling rise of Salafism (Salafiyya) remains the most visible feature of the new Islamist scene in the region. After decades of eschewing politics for theological and political reasons, Salafi movements and groups have rushed into electoral politics enthusiastically. They became keen to form political parties, contest elections, and vie for power. In Egypt, the Salafi parties fared well in the post‐revolution parliamentary elections and are a key player in drafting Egypt's new constitution. This article explores the rise of Salafism after Mubarak and examines its effects on the democratic transition in Egypt. It investigates the ideological and theological stance of Salafi movements and parties on politics and democracy in particular. The argument put forward is that the extraordinary political openness in Egypt after the revolution has pushed Salafis into everyday politics. Subsequently, Salafis have become more inclined to adopt a pragmatic and practical discourse. Based on field research, this article provides a thematic analysis of Egyptian Salafism and assesses its political future.     

STATISTICAL PROPERTIES OF MATHEMATICAL PROGRAMMING MODELS OF STOCHASTIC NETWORK EQUILIBRIUM*

ABSTRACT. Boyce et al. (1981, 1983) have proposed and implementd the use of observed entropy levels to estimate the travel-cost coefficient in mathematical programming models of network equilibrium which involve logit route-choice probabilities. This so-called “dispersion-constrained” model is shown to give severely biased and statistically inefficient underestimates. A natural counterpart, the entropy-maximizing model, is proposed here and overestimates the travel-cost coefficient with much lower bias and much higher statistical efficiency. Even though the two models are mathematically homeomorphic in some respects, they have vastly different statistical properties. It follows that the use of observed entropy levels is undesirable and should be avoided, since maximizing entropy provides an unambiguously superior alternative.     

A REGIONAL ECONOMY,LAND USE,AND TRANSPORTATION MODEL (RELU‐TRAN©): FORMULATION,ALGORITHM DESIGN,AND TESTING*

ABSTRACT RELU is a dynamic general equilibrium model of a metropolitan economy and its land use, derived by unifying in a theoretically valid way, models developed by one of the authors [ Anas (1982) , Anas–Arnott (1991, 1997) , Anas–Kim (1996) , Anas–Xu (1999) ]. RELU equilibrates floor space, land and labor markets, and the market for the products of industries, treating development (construction and demolition), spatial interindustry linkages, commuting, and discretionary travel. Mode choices and equilibrium congestion on the highway network are treated by unifying RELU with the TRAN algorithm of stochastic user equilibrium [ Anas–Kim (1990) ]. The RELU‐TRAN algorithm's performance for a stationary state is demonstrated for a prototype consisting of 4‐building, 4‐industry, 4‐labor‐type, 15‐land‐use‐zone, 68‐link‐highway‐network version of the Chicago MSA. The algorithm solves 656 equations in a special block‐recursive convergent procedure by iterations nested within loops and loops within cycles. Runs show excellent and smooth convergence from different starting points, so that the number of loops within successive cycles continually decreases. The tests also imply a numerically ascertained unique stationary equilibrium solution of the unified model for the calibrated parameters.