A knowledge-based system for controlling automobile traffic

Transportation network capacity variations arising from accidents, roadway maintenance activity, and special events as well as fluctuations in commuters' travel demands complicate traffic management. Artificial intelligence concepts and expert systems can be useful in framing policies for incident detection, congestion anticipation, and optimal traffic management. This paper examines the applicability of intelligent route guidance and control as decision aids for traffic management. Basic requirements for managing traffic are reviewed, concepts for studying traffic flow are introduced, and mathematical models for modeling traffic flow are examined. Measures for quantifying transportation network performance levels are chosen, and surveillance and control strategies are evaluated. It can be concluded that automated decision support holds great promise for aiding the efficient flow of automobile traffic over limited-access roadways, bridges, and tunnels

Initial Financial Assessment of the Fraport Greece Cluster A Concession

There is a worldwide trend in the privatization of transport infrastructure and airports. Likewise, the Greek government launched an extensive privatization program that granted Fraport AG the right to operate 14 airports for the next forty years. The two separate concessions for clusters of seven airports each are named Cluster A and Cluster B. The financial assessment of privatization contracts is crucial so decision-makers can accurately assess the value of aviation enterprises. This paper applies the Economic Value Added (EVA) methodology and enterprise valuation on Cluster A by assessing the concession company\u27s balance sheets and income statements. We concluded that Cluster A has a high Debt-to-Equity (D/E) ratio but also outstanding results when examining profitability ratios. After the adverse effects of the COVID-19 pandemic, we discovered that the concession has a vast potential for development and profitability. Overall, the privatization has successfully transferred operating risk to the concessionaire while ensuring timely airport upgrading/refurbishment. Finally, a high level of services has been attained, as evidenced that during the 2022 Airport Service Quality (ASQ) Awards Thessaloniki Makedonia Airport was recognized as one of the top airports in Europe in the category of airports that handle 5-15 million passengers per year

Composite Criticality in Machinery Fleet Management of Construction Projects

During construction operations, fleet management aims at maximizing the uptime and efficiency of construction machinery while also minimizing the cost of ownership through lifecycle planning and management. In the deterministic approach, the theory suggests that one type of machinery is considered to be critical. However, taking into account the real circumstances under which projects are performed with issues such as machine reliability, worker performance, and/or errors in estimating the scope of work, it is evident that there are significant limitations to the existing approach. Hence, to address this issue, uncertainty in fleet productivity is modelled with fuzzy set theory. In this context, the notion of composite criticality under which the productivity of a fleet depends on more than one type of machinery because of the fluctuations of the individual productivities is introduced. To this purpose, a simple case study is presented to illustrate this concept. It is concluded that this approach leads to a better understanding of the estimation of activity duration and cost estimation which in turn means better project scheduling and financial planning

A New Approach to Studying Net Present Value and the Internal Rate of Return of Engineering Projects under Uncertainty with Three-Dimensional Graphs

Cost-benefit analysis (CBA) is very useful when appraising engineering projects and examining their long-term financial and social sustainability. However, the inherent uncertainty in the estimation of completion time, final costs, and the realization of benefits often act as an impediment to its application. Since the emergence of fuzzy set theory, there have been significant developments in uncertainty modelling in project evaluation and investment analysis, primarily in the area of formulating a fuzzy version of CBA. In this context, in studying the key indicators of CBA, whereas fuzzy net present value (fNPV) has been investigated quite extensively, there are significant issues in the calculation of fuzzy internal rate of return (fIRR) that have not been addressed. Hence, this paper presents a new conceptual model for studying and calculating fNPV and fIRR. Three-dimensional fNPV and fIRR graphs are introduced as a means of visualizing uncertainty. A new approach is presented for the precise calculation of fIRR. To facilitate practical application, a computerization process is also presented. Additionally, the proposed methodology is exemplified in a sample motorway project whereby its advantages over traditional stochastic uncertainty modelling techniques such as Monte Carlo analysis are discussed. Overall, it is concluded that the new approach is very promising for modelling uncertainty during project evaluation for both project managers and project stakeholders

Scheduling and financial planning of projects and portfolios with fuzzy constraints

Scheduling and financial planning is hindered when it is based on fuzzy data. Thus, the validity of the main estimates, such as completion time, final cost and the expected cash flow is seriously affected. Moreover, projects are implemented in regard to time and cost constraints, the values of which cannot be precisely defined because of their intrinsic fuzziness. Therefore, the margin for improvement should be investigated, so that the scheduling and financial planning in regard to fuzzy constraints becomes more reliable and realistic.This Doctoral Thesis is aimed at investigating the importance and influence of Fuzzy Set Theory in scheduling and financial planning. Furthermore, it aims at developing a multi-level approach to the analysis and processing of scheduling and financial planning data in different management levels, i.e., project activities, projects, portfolios of projects and programmes of projects. Finally, the determination of the degree of fuzziness of the data that is necessary for scheduling and financial planning isinvestigated.The starting point of the research was to identify the margin for improvement in terms of dealing with fuzziness in existing scheduling and financial planning methodologies. To this end, a literature review and an evaluation of research efforts and practices in this field was conducted. Essentially, theThesis adapts elements of Fuzzy Set Theory to existing methodologies in order to model fuzziness. Finally, a software application was developed in the MATLAB computer programming environment for the implementation of new algorithms and the presentation of the results of the proposedmethodologies. The Thesis attempts to combine the duration and cost estimates, while there is also a uniform approach to the analysis and processing of data at different levels of detail. Specifically:i) At the project activity level, a methodology is presented for the estimation of the fuzzy duration and cost of activities.ii) In the special case of linear and repetitive projects the Fuzzy-Repetitive Scheduling Model (FRSM) was developed. In terms of the financial planning of projects, the concept of the S-Surface waspresented.iii) At the level of the portfolios of projects, the focus is on optimizing the use of shared resources with resource leveling techniques and heuristic algorithms.iv) At the level of programmes of projects, the impacts of fuzziness of individual projects on the cost and duration of the entire programme are examined. Additionally, elements from the scientific area of project cost-benefit analysis are combined with the theory of programme benefits management.The findings of the Thesis may be used collectively or individually in order to assist in scheduling and financial planning. Project managers can implement a methodology in one or several levels. New concepts that contribute to the development of scientific knowledge in scheduling and financial planning were developed. Finally, because the proposed methodologies are similar with existing scheduling and planning techniques, they could potentially be rapidly integrated within many practical applications.Ο χρονικός και ο οικονομικός προγραμματισμός δυσχεραίνεται όταν υπάρχει ασάφεια στα δεδομένα βάσει των οποίων εκπονείται. Έτσι, επηρεάζεται σημαντικά η εγκυρότητα των κύριων εκτιμήσεων, όπως ο χρόνος ολοκλήρωσης, το τελικό κόστος και οι αναμενόμενες χρηματοροές. Εξάλλου, τα έργα υλοποιούνται σε σχέση με περιορισμούς χρόνου και κόστους, οι τιμές των οποίων δεν μπορούν να προσδιορισθούν επακριβώς καθώς έχουν εγγενή ασάφεια. Συνεπώς, θα πρέπει να διερευνηθούν τα περιθώρια βελτίωσης, ώστε ο χρονικός και o οικονομικός προγραμματισμός σε σχέση με ασαφείς περιορισμούς να γίνει πιο αξιόπιστος και ρεαλιστικός.Η Διδακτορική Διατριβή (ΔΔ) αποσκοπεί στη διερεύνηση της σημασίας και της επιρροής της θεωρίας της ασάφειας στον χρονικό και οικονομικό προγραμματισμό. Περαιτέρω, επιδιώκεται η ανάπτυξη μιας πολύ-επίπεδης προσέγγισης για την ανάλυση και επεξεργασία των δεδομένων χρονικού και οικονομικού προγραμματισμού σε διαφορετικά επίπεδα διοίκησης-διαχείρισης, δηλαδή, δραστηριότητας έργου, έργου, χαρτοφυλακίου έργων και προγράμματος έργων. Τέλος, εξετάζεται ο προσδιορισμός του βαθμού της ασάφειας των δεδομένων που είναι απαραίτητα στον χρονικό και οικονομικό προγραμματισμό. Αφετηρία της έρευνας αποτέλεσε ο εντοπισμός των περιθωρίων βελτίωσης ως προς τη διαχείριση της ασάφειας στις υπάρχουσες μεθοδολογίες χρονικού και οικονομικού προγραμματισμού. Για τον σκοπό αυτόν, πραγματοποιήθηκε βιβλιογραφική ανασκόπηση και αξιολόγηση των μέχρι σήμερα ερευνητικών προσπαθειών και πρακτικών στο συγκεκριμένο πεδίο. Έτσι, κατά κύριο λόγο, στη ΔΔ προσαρμόζονται στοιχεία της θεωρίας της ασάφειας σε υπάρχουσες μεθοδολογίες προγραμματισμού ώστε να μοντελοποιηθεί η ασάφεια. Τέλος, για την εφαρμογή των νέων αλγορίθμων και την παρουσίαση των αποτελεσμάτων των προτεινόμενων μεθοδολογιών αναπτύχθηκε εφαρμογή σε ηλεκτρονικό υπολογιστή στο περιβάλλον προγραμματισμού MATLAB. Στη ΔΔ επιχειρείται ο συνδυασμός των εκτιμήσεων χρόνου και κόστους, ενώ παράλληλα υπάρχει μια ενιαία προσέγγιση ως προς την ανάλυση και επεξεργασία των δεδομένων σε διαφορετικά επίπεδα λεπτομέρειας. Ειδικότερα:i) Στο επίπεδο της δραστηριότητας έργου, παρουσιάζεται μεθοδολογία υπολογισμού της ασάφειας στον χρόνο και στο κόστος δραστηριοτήτων.ii) Στην ειδική κατηγορία των γραμμικών και επαναληπτικών έργων, αναπτύχθηκε μεθοδολογία ασαφούς χρονικού προγραμματισμού επαναληπτικών έργων Fuzzy-Repetitive Scheduling Model (F-RSM). Στον οικονομικό προγραμματισμό έργων παρουσιάστηκε η έννοια της επιφάνειας-S (SSurface).iii) Στο επίπεδο του χαρτοφυλακίου έργων, δίνεται έμφαση στη βελτιστοποίηση της χρήσης των κοινών μέσων παραγωγής με τεχνικές εξισορρόπησης πόρων και ευρετικές μεθόδους.iv) Στο επίπεδο της διαχείρισης προγραμμάτων, εξετάζεται η επίδραση της ασάφειας μεμονωμένων έργων στο κόστος και στον χρόνο του συνολικού προγράμματος. Επιπρόσθετα, συνδυάζονται στοιχεία από το επιστημονικό πεδίο των αναλύσεων κόστους-οφέλους έργων με τη διαχείριση των ωφελειών προγράμματος (benefits management).Τα ευρήματα της ΔΔ μπορούν συνολικά ή ξεχωριστά να υποβοηθήσουν τον χρονικό και τον οικονομικό προγραμματισμό. Οι διαχειριστές έργων μπορούν να εφαρμόσουν μια μεθοδολογία σε ένα ή σε πολλά επίπεδα. Σημειώνεται ότι αναπτύχθηκαν νέες έννοιες που συμβάλλουν στην ανάπτυξη της επιστημονικής γνώσης στον χρονικό και οικονομικό προγραμματισμό. Τέλος, επειδή οι προτεινόμενες μεθοδολογίες έχουν αρκετά κοινά σημεία με τις παρούσες τεχνικές προγραμματισμού έργων, θα μπορούσαν δυνητικά να ενσωματωθούν ταχύτατα σε πολλές πρακτικές εφαρμογές