The use of floating car data as a particular case of probe vehicle data has been the object of extensive research for estimating traffic conditions, travel times, and origin-to-destination trip matrices. It is based on data collected from a GPS-equipped vehicle fleet or available cell phones. Cooperative cars with vehicle-to-vehicle and vehicle-to-infrastructure communication capabilities represent a step forward, as they also allow tracking of vehicles surrounding the equipped car. This paper presents the results of a limited experiment with a small fleet of cooperative cars in the central business district of Barcelona, Spain, known as L’Eixample District. Data collected from the experiment were used to build and calibrate the emulation of cooperative functions in a microscopic simulation model that captured the behavior of vehicle sensors in Barcelona’s central business district. Such a calibrated model allows emulating fleet data on a large scale that goes far beyond what a small fleet of cooperative vehicles could capture. To determine the traffic state, several approaches were developed for estimating traffic variables—whose accuracy depends on the penetration level of the technology—on the basis of extensions of Edie’s generalized definitions of the fundamental traffic variables with the emulated data.
The paper presents the effects of Dynamic Speed Limit control (DSL) in a 3 lane section on the A13 freeway, in Rotterdam. The main objective is to contrast the latest empirical findings in Barcelona , where the mainline metering capability (i.e. gating, meaning mainline flow restriction) due to sub-critical speed limits (e.g. down to 40 km/h) was questioned. Moreover, according to the Barcelona results, the validity of the current fundamental diagram models accounting for DSL could be strongly compromised.
This investigation takes advantage of the huge empirical traffic database recorded by the Dutch government and of DSL strategies being present on most of their freeways. Data is treated in order to identify stationary periods of traffic. A method, reproducible elsewhere, and computerized into an algorithm has been developed to this end. The fundamental diagram is used as a graphical tool to assess the results.
The main findings do not contradict the Barcelona observations. Flows of 1850 veh/h per lane were steadily observed for the sub-critical speed limit of 50 km/h. The reactive nature of the DSL-control implemented in the Netherlands, implies that very low speed limits do not affect a wide range of traffic states. This hampered the possibility of extending this conclusion. Further research with less limiting DSL control strategies would be necessary to clarify the extent of the phenomenon considered.
The choice to use horizontal handling transport in automated container terminals is not fully consistent in comparison with the automation of stacking cranes at the storage yard. Often the decision of whether to use an automated system between the berth and the yard area is not clear, and terminal operators tend not to use automated systems. The goal of this paper is to provide an economic analysis to determine under which conditions automated horizontal transport is more efficient than a semiautomated system. The study provided several simulation models to calculate the optimal equipment necessary to connect storage and berth subsystems in a maritime container terminal in fully automated and semiautomated scenarios. Data from the semiautomated container terminal at the Port of Barcelona, Spain, were used. In addition to the cost analysis, guidelines on the best alternative, considering labor costs, throughput movements per quay crane and year, and quay crane productivity are provided.
Many first-order macroscopic models for freeway traffic have been developed since the seminal work on the well-known Lighthill-Whitham-Richards, or LWR, continuous model. The asymmetric cell transmission model (ACTM) is a widely accepted macroscopic model integrated into a variety of freeway traffic control frameworks. The model is based on the original cell transmission model; modified merge equations make it computationally tractable for optimization of ramp metering. However, when the common simplistic calibration of the model is used, an infeasible merging behavior is observed at uncontrolled merges, and the resulting queue lengths are not accurately estimated. This paper proposes an elegant analytical relationship, based on traffic flow theory, for calibrating the two parameters involved in the ACTM merge model. The method ensures the physical consistency of the dynamics involved in queue processes in the proximity of a noncontrolled merge junction. This method should be an essential feature of any freeway traffic model.
Origin–destination (O-D) trip matrices that describe the patterns of
traffic behavior across a network are the primary data input used in
principal traffic models and, therefore, a critical requirement in all
advanced systems supported by dynamic traffic assignment models.
However, because O-D matrices are not directly observable, the current
practice consists of adjusting an initial or seed matrix from link
flow counts that are provided by an existing layout of traffic-counting
stations. The availability of new traffic measurements provided by information
and communication technologies (ICT) allows more efficient
algorithms, namely for real-time estimation of O-D matrices that are
based on modified Kalman filtering approaches to exploit the new data.
The quality of the estimations depends on various factors such as the
penetration of the ICT devices, the detection layout, and the quality of
the initial information. The feasibility of real-time applications depends
on the computational performance of the proposed algorithms for urban
networks of sensitive size. This paper presents the results of a set of
computational experiments with a microscopic simulation of the network
of Barcelona’s central business district that explore the sensitivity of the
Kalman filter estimates in relation to design factor values.
Origin–destination (O-D) trip matrices that describe the patterns of traffic behavior across a network are the primary data input used in principal traffic models and, therefore, a critical requirement in all advanced systems supported by dynamic traffic assignment models. However, because O-D matrices are not directly observable, the current practice consists of adjusting an initial or seed matrix from link flow counts that are provided by an existing layout of traffic-counting stations. The availability of new traffic measurements provided by information and communication technologies (ICT) allows more efficient algorithms, namely for real-time estimation of O-D matrices that are based on modified Kalman filtering approaches to exploit the new data. The quality of the estimations depends on various factors such as the penetration of the ICT devices, the detection layout, and the quality of the initial information. The feasibility of real-time applications depends on the computational performance of the proposed algorithms for urban networks of sensitive size. This paper presents the results of a set of computational experiments with a microscopic simulation of the network of Barcelona’s central business district that explore the sensitivity of the Kalman filter estimates in relation to design factor values.
The importance of binder performance on the mixture response to accelerated fatigue loading and thermal cracking was investigated. Binder’s fatigue performance was measured by means of the Linear Amplitude Sweep test (LAS) while fatigue properties of the mixtures were investigated by performing the EBADE test. The low temperature properties of the binders were investigated by measuring the glass transition temperature and fracture properties with the Single Edge Notched Beam (SENB) test. The mixtures fracture properties were investigated using the FENIX test. The experimental matrix for this study included unmodified and rubber-modified binders and limestone aggregates. A good correlation between binder and mixture fracture energy was observed at low temperatures. This good correlation indicates the importance of fracture response of the binder to the overall low temperature cracking performance of the mixture. Experimental results suggest that a significant part of the variation of the fracture energy of the mixture can be explained by the binder fracture properties. Good correlations were also obtained for the displacement at maximum load in the SENB and Fenix tests. Similar accelerated fatigue response for binders and mixtures were observed when the stresses and strains were normalized. Significant reduction in the stress happened at about the same normalized strain in the binder and mixture. It can be seen that the mixture has remaining strength after reaching peak stress probably due to the aggregate structure.
The primary data input used in principal traffic models comes from Origin-Destination (OD) trip matrices, which describe the patterns of traffic behavior across the network. In this way, OD matrices become a critical requirement in Advanced Traffic Management and/or Information Systems that are supported by Dynamic Traffic Assignment models. However, because OD matrices are not directly observable, the current practice consists of adjusting an initial or seed matrix from link flow counts which are provided by an existing layout of traffic counting stations. The adequacy of the detection layout strongly determines the quality of the adjusted OD. The usual approaches to the Detection Layout problem assume that detectors are located at network links. The first contribution of this paper proposes a modified set that formulates the link detection layout problem with side constraints. It also presents a new metaheuristic tabu search algorithm with high computational efficiency. The emerging Information and Communication Technologies, especially those based on the detection of the electronic signature of on-board devices (such as Bluetooth devices) allow the location of sensors at intersections. To explicitly take into account how these ICT sensors operate, this paper proposes a new formulation in terms of a node covering problem with side constraints that, for practical purposes, can be efficiently solved with standard professional solvers such as CPLEX.
From the point of view of the information supplied by an ATIS to the motorists entering a freeway of one of the most relevant is the Forecasted Travel Time, that is the expected travel time that they will
experience when traverse a freeway segment. From the point of view of ATMS the dynamic estimates of time dependencies in OD matrices is a major input to dynamic traffic models used for estimating the current traffic state and forecasting its short term evolution. Travel Time Forecasting and Dynamic OD Estimation are two of the key components of ATIS/ATMS and the quality of the results that they could provide depend not only on the quality of the models but also on the accuracy and reliability of
the measurements of traffic variables supplied by the detection technology.
The quality and reliability of the measurements produced by traditional technologies, as inductive loop detectors, is not usually the required by real-time applications, therefore one wonders what could be expected from the new ICT technologies as for example Automatic Vehicle Location, License Plate Recognition, detection of mobile devices and so on. The main objectives of this paper are: to explore
the quality of the data produced by the Bluetooth detection of mobile devices equipping vehicles for Travel Time Forecasting and its use to estimate time dependent OD matrices. Ad hoc procedures
based on Kalman Filtering have been designed and implemented successfully and the numerical results of the computational experiments are presented and discussed.
This paper presents a new direct tensile test to evaluate cracking resistance of asphalt concrete mixtures called Fénix test. First, the literature on cracking factors and mechanisms of bituminous mixtures as well as current tests to measure cracking properties are reviewed. Next, the Fénix
test is described and some initial experimental results of the influence of variables such as binder type and content and test temperature are provided. Additionally, test repeatability and sensitivity are statistically analyzed. Correlations between parameters obtained by the Fénix test and the three-point bending beam fatigue test are also shown. Finally, the main conclusions of this work are summarized. These conclusions confirm that the Fénix test is a practical and efficient method for characterizing cracking behaviour of asphalt concrete mixtures as far as the studied variables are concerned.
This paper defines some compact expressions to evaluate the average distance traveled in VRP problems in circular and elliptic zones. These formulas have been carried out empirically from the results obtained by the
application to a set of problems of heuristic algorithms (Clarke & Wright, Fisher & Jaikumar and Gillet & Miller) and Daganzo’s method based on continuous approximations of the demand spatial distribution.
The problems are solved and designed automatically by a computer. Vehicle capacity has been the only constraint considered in the tour design. If N is the number of points and C is the vehicle capacity, it has been shown that the Clarke and Wright algorithm provides the best solutions especially when N<50 or N/C<14. On
the other hand, solutions with Daganzo’s method are not adequate when N/C≤3.
The works carried out within the framework of the development of an automatic system for permit vehicle routing on the Spanish National Highway network are described. The focus is on the methodology adopted for analysis of the old existing bridges. Because information about bridge properties (geometry, material strength) and design live load is unknown, the evaluation procedure combines the information provided by in situ measurements and inspection with a reliability-based evaluation. The reliability index for the most critical limit states derived from the maximum effects due to actual traffic on the bridge is adopted as the comparison value to define a passage criterion. Any permit crossing the bridge alone or with traffic restrictions leading to a lower reliability index will not be allowed on the bridge. The actual traffic load is obtained from existing traffic records using a model of traffic flow. The method is applied to 10 bridges fully representative of the old and nondocumented bridges most often encountered on Spanish highways. The final result is definition of the standard permits as presented in Eurocode 1 that are allowed on the bridge. From the most unfavorable permit, a criterion is derived concerning the actual vehicle permits.
Different bridge types and design configurations used in bridge engineering result in largely different dynamic mechanisms of response. Therefore, one of the most important problems to resolve about their theoretical dynamic modeling is to choose the most adequate and simple model for a particular bridge. The work carried out during the dynamic testing of several bridges is reviewed. The objective was to check the feasibility and accuracy of various numerical and analytical models assumed for the dynamic behavior of various bridge types (box-girder, slab bridges, and cable-stayed). Experimental field test data were used to derive the dynamic properties of the bridges. The most appropriate analytical models and dynamic properties of the elements used in the discretization mesh were derived for each bridge type on the basis of the correlation between the theoretical and experimental results. Taking these results into account, a set of practical recommendations for the dynamic modeling of different bridge types is proposed.