Estimation of aggregated modal split mode

In spite of the fact that disaggregate modelling has undergone considerable development in the last twenty years, many studies are still based on aggregate modelling. In France, for example, aggregate models are still in much more common use than disaggregate models, even for modal split. The estimation of aggregate models is still therefore an important issue.In France, for most studies it is possible to use behavioural data from household surveys, which are conducted every ten years in most French conurbations. These household surveys provide data on the socioeconomic characteristics both of individuals and the households to which they belong and data on modal choice for all the trips made the day before the survey. The sampling rate is generally of 1% of the population, which gives about 50,000 trips for a conurbation of 1 million inhabitants. However, matrices that contain several hundred rows and columns are frequently used. We therefore have to construct several modal matrices that contain more than 10,000 cells (in the case of a small matrix with only 100 rows) with less than 50,000 trips (to take the above example). Obviously, the matrices will contain a large number of empty cells and the precision of almost all the cells will be very low. It is consequently not possible to estimate the model at this level of zoning.The solution which is generally chosen is to aggregate zones. This must comply with two contradictory objectives:- the number of zones must be as small as possible in order to increase the number of surveyed trips that can be used during estimation and hence the accuracy of the O-D matrices for trips conducted on each mode;- the zones must be as small as possible in order to produce accurate data for the explanatory variables such as the generalized cost for each of the transport modes considered. When the size of the zone increases, it is more difficult to evaluate the access and regress time for public transport and there are several alternative routes with different travel times between each origin zone and each destination. Therefore more uncertainty is associated with the generalized cost that represents the quality of service available between the two zones. The generally adopted solution is to produce a weighted average of all the generalized costs computed from the most disaggregated matrix. However, there is no guarantee that this weighted mean will be accurate for the origin-destination pair in question.When the best compromise has been made, some of the matrix cells are generally empty or suffer from an insufficient level of precision. To deal with this problem we generally keep only the cells for which the data is sufficiently precise by selecting those cells in which the number of surveyed trips exceeds a certain threshold. However, this process involves rejecting part of the data which cannot be used for estimation purposes. When a fairly large number of zones is used, the origin destination pairs which are selected for the estimation of the model mainly involve trips that are performed in the centre of the conurbation or radial trips between the centre and the suburbs. These origin-destination pairs are also those for which public transport's share is generally the highest. The result is to reduce the variance of the data and therefore the quality of the estimation.To cope with this problem we propose a different aggregation process which makes it possible to retain all the trips and use a more disaggregate zoning system. The principle of the method is very simple. We shall apply the method to the model most commonly used for modal split, which is the logit model. When there are only two modes of transport, the share of each mode is obtained directly from the difference in the utility between the two modes with the logit function. We can therefore aggregate the origin-destination pairs for which the difference between the utility of the two modes is very small in order to obtain enough surveyed trips to ensure sufficient data accuracy. This process is justified by the fact that generally the data used to calculate the utility of each mode is as accurate or even more accurate at a more disaggregate level of zoning. The problem with this method is that the utility function coefficients have to be estimated at the same time as the logit model. An iterative process is therefore necessary. The steps of the method are summarised below:- selection of initialization values for the utility function coefficients for the two transport modes in order to intitialize the iteration process. These values can, for example, be obtained from a previous study or calibration performed according to the classical method described in Section 1.2;- the utility for each mode is computed on the basis of the above coefficients, followed by the difference in the utility for each O-D pair in the smallest scale zoning system for which explanatory variables with an adequate level of accuracy are available (therefore with very limited zonal aggregation or even none at all);- the O-D pairs are classified on the basis of increasing utility difference;- the O-D pairs are then aggregated. This is done on the basis of closeness of utility difference. The method involves taking the O-D link with the smallest utility difference then combining it with the next O-D pair (in order of increasing utility difference). This process is continued until the number of surveyed trips in the grouping is greater than a threshold value that is decided on the basis of the level of accuracy that is required for trip flow estimation. When this threshold is reached the construction of the second grouping is commenced, and so on and so forth until each O-D pair has been assigned to a group;- for each new class of O-D pairs it is necessary to compute the values of the explanatory variables which make up the utility functions for each class. This value is obtained on the basis of the weighted average of the values for each O-D pair in the class;- a new estimation of the utility function coefficients.This process is repeated until the values of the utility function coefficients converge. We have tested this method for the Lyon conurbation with data from the most recent household travel survey conducted in 1995/96. We have conducted a variety of tests in order to identify the best application of the method and to test the stability of the results. It would seem that this method always produces better results than the more traditional method that involves zoning aggregation. The paper presents both the methodology and the results obtained from different aggregation methods. In particular, we analyse how the choice of zoning system affects the results of the estimation.Aggregate modelling ; choice modal ; Zoning system ; Urban mobility ; Conurbation (Lyon, France) ; Estimation method

Analysis of principal trends of mobility related to location policy, car ownership, supply policy and ageing of population

In transport analysis, we generally have several correlative explanatory variables when we want to explain the evolution of a factor. Therefore the quantification of the contribution of each variable in the evolution of our study object is often problematic. This problem is well known in modelling even if not always well treated. In this case the evolution of the object cannot always be expressed simply (as a sum or a product) from the evolution of the explanatory variables. To take this question into account, we propose a method to break down and measure the effect of each explanatory variable. We have applied this method to two contexts which focus the thematic network on Society, Behaviour and Private/Public Transport.The first one deals with a retrospective analysis of the evolution of car ownership and car use of both elderly people and younger people. This analysis permits to quantify the contribution of different factors: demographic effect, car ownership effect and behaviour effect and their combination to quantify the evolution of the number of car trips in the population. This analysis has been conducted both in Lyon and Grenoble conurbation in south-east of France from several household surveys conducted between 1970 and 1995.The second one analyses the evolution of the share of public transport among motorised trips in the Lyon conurbation. This analysis allows to quantify the contribution of different factors: urban sprawl effect, car ownership effect, public transport supply effect, private transport supply effect and a residual effect which summarised unobserved variables and their combination to quantify the evolution of public transport share among motorised transport. It explains the apparent paradox of a very important increase in public transport supply in Lyon conurbation but a stability of the share of public transport between 1976 and 1995.Both analysis suggest interesting features both in term of prospective and urban policy. It appears that very strong socio-demographic trends act to reduce, when not cancel, the effect of important improvement in public transport supply as we can see in many French conurbation. From the quantification of different effects, we can simulate different future from which it appears that only global and comprehensive policy on all mode of transport and parking and on urbanism are able to reduce use of car in sustainable perspective.Urban mobility ; car ownership ; urban sprawl ; aging of population ; public transport ; trends ; cohort effect ; simulation

Optimality Conditions for Semivectorial Bilevel Convex Optimal Control Problems

We present optimality conditions for bilevel optimal control problems where the upper level, to be solved by a leader, is a scalar optimal control problem and the lower level, to be solved by several followers, is a multiobjective convex optimal control problem. Multiobjective optimal control problems arise in many application areas where several conflicting objectives need to be considered. Minimize several objective functionals leads to solutions such that none of the objective functional values can be improved further without deteriorating another. The set of all such solutions is referred to as efficient (also called Pareto optimal, noninferior, or nondominated) set of solutions. The lower level of the semivectorial bilevel optimal control problems can be considered to be associated to a ”grande coalition” of a p-player cooperative differential game, every player having its own objective and control function. We consider situations in which these p-?players react as ”followers” to every decision imposed by a ”leader” (who acts at the so-called upper level). The best reply correspondence of the followers being in general non uniquely determined, the leader cannot predict the followers choice simply on the basis of his rational behavior. So, the choice of the best strategy from the leader point of view depends of how the followers choose a strategy among his best responses. In this paper, we will consider two (extreme) possibilities: (i) the optimistic situation, when for every decison of the leader, the followers will choose a strategy amongst the efficient controls which minimizes the (scalar) objective of the leader; in this case the leader will choose a strategy which minimizes the best he can obtain amongst all the best responses of the followers: (ii) the pessimistic situation, when the followers can choose amongst the efficient controls one which maximizes the (scalar) objective of the leader; in this case the leader will choose a strategy which minimizes the worst he could obtain amongst all the best responses of the followers. This paper continues the research initiated in [17] where existence results for these problems have been obtained.

Discrete Elastic Inner Vector Spaces with Application in Time Series and Sequence Mining

This paper proposes a framework dedicated to the construction of what we call discrete elastic inner product allowing one to embed sets of non-uniformly sampled multivariate time series or sequences of varying lengths into inner product space structures. This framework is based on a recursive definition that covers the case of multiple embedded time elastic dimensions. We prove that such inner products exist in our general framework and show how a simple instance of this inner product class operates on some prospective applications, while generalizing the Euclidean inner product. Classification experimentations on time series and symbolic sequences datasets demonstrate the benefits that we can expect by embedding time series or sequences into elastic inner spaces rather than into classical Euclidean spaces. These experiments show good accuracy when compared to the euclidean distance or even dynamic programming algorithms while maintaining a linear algorithmic complexity at exploitation stage, although a quadratic indexing phase beforehand is required.Comment: arXiv admin note: substantial text overlap with arXiv:1101.431

Trans-dimensional inversion of modal dispersion data on the New England Mud Patch

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Bonnel, J., Dosso, S. E., Eleftherakis, D., & Chapman, N. R. Trans-dimensional inversion of modal dispersion data on the New England Mud Patch. IEEE Journal of Oceanic Engineering, 45(1), (2020): 116-130, doi:10.1109/JOE.2019.2896389.This paper presents single receiver geoacoustic inversion of two independent data sets recorded during the 2017 seabed characterization experiment on the New England Mud Patch. In the experimental area, the water depth is around 70 m, and the seabed is characterized by an upper layer of fine grained sediments with clay (i.e., mud). The first data set considered in this paper is a combustive sound source signal, and the second is a chirp emitted by a J15 source. These two data sets provide differing information on the geoacoustic properties of the seabed, as a result of their differing frequency content, and the dispersion properties of the environment. For both data sets, source/receiver range is about 7 km, and modal time-frequency dispersion curves are estimated using warping. Estimated dispersion curves are then used as input data for a Bayesian trans-dimensional inversion algorithm. Subbottom layering and geoacoustic parameters (sound speed and density) are thus inferred from the data. This paper highlights important properties of the mud, consistent with independent in situ measurements. It also demonstrates how information content differs for two data sets collected on reciprocal tracks, but with different acoustic sources and modal content.10.13039/100000006-Office of Naval Research 10.13039/100007297-Office of Naval Research Globa

Nonlinear time-warping made simple: a step-by-step tutorial on underwater acoustic modal separation with a single hydrophone

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Bonnel, J., Thode, A., Wright, D., & Chapman, R. Nonlinear time-warping made simple: a step-by-step tutorial on underwater acoustic modal separation with a single hydrophone. The Journal of the Acoustical Society of America, 147(3), (2020): 1897, doi:10.1121/10.0000937.Classical ocean acoustic experiments involve the use of synchronized arrays of sensors. However, the need to cover large areas and/or the use of small robotic platforms has evoked interest in single-hydrophone processing methods for localizing a source or characterizing the propagation environment. One such processing method is “warping,” a non-linear, physics-based signal processing tool dedicated to decomposing multipath features of low-frequency transient signals (frequency f  1 km). Since its introduction to the underwater acoustics community in 2010, warping has been adopted in the ocean acoustics literature, mostly as a pre-processing method for single receiver geoacoustic inversion. Warping also has potential applications in other specialties, including bioacoustics; however, the technique can be daunting to many potential users unfamiliar with its intricacies. Consequently, this tutorial article covers basic warping theory, presents simulation examples, and provides practical experimental strategies. Accompanying supplementary material provides matlab code and simulated and experimental datasets for easy implementation of warping on both impulsive and frequency-modulated signals from both biotic and man-made sources. This combined material should provide interested readers with user-friendly resources for implementing warping methods into their own research.This work was supported by the Office of Naval Research (Task Force Ocean, project N00014-19-1-2627) and by the North Pacific Research Board (project 1810). Original warping developments were supported by the French Delegation Generale de l'Armement

Poverty Reduction Strategies: Their Importance for Disability

[Excerpt] In recent years, Poverty Reduction Strategy Papers (PRSPs) have made substantial headway in increasing country ownership of poverty reduction strategies and opening the policy dialogue between government and civil society. In the process, PRSPs have emerged as a key instrument for reducing the poverty of poor households. There is a wide consensus that disabled persons, being disproportionately poor, are among the population groups that should benefit from the poverty reduction programs of PRSPs. The issue, however, is whether they are de facto excluded from benefiting from current poverty reduction strategies. As argued by the ILO, PRSPs do not meet the needs of disabled persons because they are based on a limited social protection policy that conveys a wrong impression about the abilities and aspirations of the majority of disabled persons. Furthermore, they do not reflect the basic principles of the modern approach to disability adopted by the United Nations. This report is an attempt to assess the validity of the mentioned argument by reviewing the disability policy content of PRSPs. In doing so, the report focuses on whether the specific poverty dimensions of disabled persons are acknowledged and the critical interventions for improving the economic and social integration of disabled persons are included in PRSPs

Cost effectiveness and financial sustainability in ovc plansand budget: what more needs to be done

This item is archived in the repository for materials published for the USAID supported Orphans and Vulnerable Children Comprehensive Action Research Project (OVC-CARE) at the Boston University Center for Global Health and Development

Une mesure dynamique des relations entre transports collectifs, étalement urbain et motorisation. Le cas de Lyon, 1976-1995

A l'heure où de nombreuses agglomérations en Europe cherchent à réduire ou à contenir la place de la voiture en ville pour répondre à des objectifs environnementaux ou économiques, cet article vise à quantifier la contribution de certaines tendances lourdes à l'évolution du partage modal entre les transports collectifs et la voiture. Nous examinons l'incidence de l'étalement urbain et de la croissance de la motorisation sur la part de marché des transports collectifs et de la voiture particulière. Sur l'agglomération lyonnaise, au cours de chacune des deux dernières décennies, l'évolution des localisations a été synonyme, selon la décennie et la zone d'étude, d'une perte de 6 à 9 % sur la part de marché des transports collectifs tandis que l'évolution de la motorisation (à structure spatiale des flux stable) a signifié une perte plus modérée de 1 à 4 %. Cette quantification permet d'éclairer les décideurs sur les évolutions probables de la part de marché des transports collectifs et sur l'importance de certains facteurs dans ces évolutions. Elle permet de bâtir des scénarios plus réalistes en matière de partage modal et de mesurer l'importance des efforts à consentir, ne serait-ce que pour contenir la place de l'automobile dans une perspective de développement durable.étalement urbain ; transport en commun ; transport collectif ; choix du mode de transport ; croissance de la motorisation ; répartition modale ; Lyon (France) ; agglomération lyonnaise