Real Time Traffic

This paper presents the design of a robust and real-time traffic-violation detection system for cameras on intersections. We use background segmentation and a novel road-model to obtain the candidate traffic participants. A region-based tracking system, equipped with static occlusion-reasoning, tracks the positions of the objects in the scene. A computationally efficient camera model is defined which only requires three input parameters and enables the extraction of key object parameters like vehicle type and speed. Experiments have shown that an impressive average processing rate of 63-150 Hz is achieved, with high average correct road detection and object-type classification rates of 93-94% and event detection accuracy of 85%.

The growing need of the driving public for accurate traffic information has spurred the deployment of large scale dedicated monitoring infrastructure systems, which mainly consist in the use of inductive loop detectors and video cameras. On-board electronic devices have been proposed as an alternative traffic sensing infrastructure, as they usually provide a cost-effective way to collect traffic data, leveraging existing communication infrastructure such as the cellular phone network. A traffic monitoring system based on GPS-enabled smartphones exploits the extensive coverage provided by the cellular network, the high accuracy in position and velocity measurements provided by GPS devices, and the existing infrastructure of the communication network. This article presents a field experiment nicknamed Mobile Century, which was conceived as a proof of concept of such a system. Mobile Century included 100 vehicles carrying a GPS-enabled Nokia N95 phone driving loops on a 10-mile stretch of I-880 near Union City, California, for 8 hours. Data were collected using virtual trip lines, which are geographical markers stored in the handset that probabilistically trigger position and speed updates when the handset crosses them. The proposed prototype system provided sufficient data for traffic monitoring purposes while managing the privacy of participants. The data obtained in the experiment were processed in real-time and successfully broadcast on the internet, demonstrating the feasibility of the proposed system for real-time traffic monitoring. Results suggest that a 2-3% penetration of cell phones in the driver population is enough to provide accurate measurements of the velocity of the traffic flow.

With the advent of the IEEE 802.11 wireless networks that provide high speed connectivity, demand for supporting multiple real-time traffic appli-cations over wireless LANs has been increasing. A natural question is how to provide fair resource allocation to real-time traffic in wireless LANs. Wireless networks are subject to unpredictable location-dependent error bursts, which is different from wired networks. We propose a fair real-time scheduling model whose goal is to minimize the maximum loss rate among all the flows and additionally to maximize the overall throughput. We de-velop algorithms for this scheduling model that takes the wireless channel error characteristics into consideration. I.

The need for increased individual mobility has resulted in a significant and continuous increase of road traffic density. More and more, the roads are getting congested. Modern Intelligent Transportation Systems (ITS) are offering methods to avoid these congestions. However, this requires a dense surveillance system of sensors that is very costly. Thus, due to financial constraints, not all roads are

This paper introduces a new real-time traffic light recognition system for on-vehicle camera applications. This approach has been tested with good results in urban scenes. Thanks to the use of our generic "Adaptive Templates" it would be possible to recognize different kinds of traffic lights from various countries.

The paper studies a train scheduling problem faced by railway infrastructure managers during real-time traffic control. When train operations are perturbed, a new conflict-free timetable of feasible arrival and departure times needs to be recomputed, such that the deviation from the original one is minimized. The problem can be viewed as a huge job shop scheduling problem with no-store constraints. We make use of a careful estimation of time separation among trains, and model the scheduling problem with an alternative graph formulation. We develop a branch and bound algorithm which includes implication rules enabling to speed up the computation. An experimental study, based on a bottleneck area of the Dutch rail network, shows that a truncated version of the algorithm provides proven optimal or near optimal solutions within short time limits.

The aim of this paper is to characterize the behavior of the UDP transport protocol, mainly in terms of throughput and average delay, over an IEEE 802.11b compliant wireless local area network (WLAN) from an experimental approach. Although performance evaluation of these kinds of LAN is being extensively discussed in the current literature, most of these studies are analytical or simulation-based and they do not consider the influence of channel impairments or link quality over network throughput. After an exhaustive measurement campaign, different performance parameters such as throughput, goodput, effective goodput, frame error rate, IT loss rate, delay and jitter have been obtained. This could be a preliminary analysis of the behavior of real-time traffic over WLAN infrastructures, such as streaming audio and voice transmission, services that are expected to undergo substantial growth in the coming years. All these studies and results have been developed in the context of the WINE (Wireless Internet Networks) project belonging to the framework of the Information Society Technologies (IST) programme, addressed to enhancing the performance of TCP/IP protocol over WLAN such as IEEE 802.11, Bluetooth and HIPERLAN/2

This paper presents the design and evaluation of a fuzzy logic trac signal controller for an isolated intersection. The controller is designed to be responsive to real-time trac demands. The fuzzy controller uses vehicle loop detectors, placed upstream of the intersection on each approach, to measure approach ows and estimate queues. These data are used to decide, at regular time intervals, whether to extend or terminate the current signal phase. These decisions are made using a two-stage fuzzy logic procedure. In the ®rst stage, observed approach trac¯ows are used to estimate relative trac intensities in the competing approaches. These trac intensities are then used in the second stage to determine whether the current signal phase should be extended or terminated. The performance of this controller is compared to that of a trac-actuated controller for dierent trac conditions on a simulated four-approach intersection. Ó (M.B. Trabia).

In this paper, we study a constraint-based routing strategy using label switching in a multi-layered hierarchical satellite constellation such as transformational communications architecture. Both quality (bit error rate on free space optical and radio inter-satellite links) and bandwidth availability on a satellite link are taken into account when setting up routes for high priority real-time traffic such as VoIP, which is sensitive to delay and jitter. To protect the real-time traffic from being swamped by bursty best-effort traffic we propose to have a ...

Heterogeneous wireless networks will be dominant in the next-generation wireless networks with the integration of various wireless access networks. Wireless mesh networks will become to a key technology as an economically viable solution for wide deployment of high speed, scalable and ubiquitous wireless Internet services.

Traffic sign recognition has been a very active research topic for many years now. However, during this time of intensive research, no common evaluation methodology has been established. This paper explains detailedly, how we evaluated our real time video-based traffic sign recognition system and thus may serve as a building block towards establishing a commonly accepted evaluation methodology. The proposed evaluation methods are taken from the visual surveillance research community, which was very active in evaluation techniques during the recent years.

Distributed computer control systems used nowadays in the industry need often to meet requirements of on-line reconfigurability so they can adjust dynamically to changes in the application environment or to evolving specifications. The communication network connecting the computer nodes, commonly a fieldbus system, must use therefore dynamic scheduling strategies, together with on-line admission control procedures that test the validity of all changes in order to guarantee the satisfaction of real-time constraints. These are both very computationally demanding tasks, something that has precluded their wide adoption. However, these algorithms also embed sufficient levels of parallelism to grant them benefits from implementations in dedicated hardware. This paper presents a scheduling coprocessor that executes dynamic real-time traffic scheduling and schedulability analysis. The FPGA-based implementation described here supports multiple scheduling policies and was tailored for the FTT-CAN protocol, but it can be used also in other fieldbuses relying on centralized scheduling. The coprocessor generates schedules in about two orders of magnitude less time than any practical network elementary cycle duration. The time to execute a schedulability test is deterministic. An evaluation based on the SAE benchmark yielded a worstcase execution time of 1.4 ms. The paper starts by discussing the scheduling problem being addressed. It describes then the coprocessor functionality and architecture, highlighting important design decisions, and its latest implementation. Finally the coprocessor performance evaluation is presented.

For having better and up to date traffic information access, spatio-temporal GIS for transportation (TGIS-T) needs to interact with the intelligent transport systems (ITS). Advanced traffic management systems (ATMS) is one of the components of the ITS and predicts traffic congestion and provides real time traffic information and optimal control strategies for freeways and arterials. ATMS needs automatic acquisition of traffic information such as traffic volume using different detectors. In fact, the ideal condition for ATMS is the one in which all urban intersections are equipped with these detectors, however, it would not be possible in short time. So, the urban intersection degree of importance recognition in order to consider the priority as well as planning for detectors installation is one of the main traffic control designers' challenges. In this paper, an approach has been proposed and implemented to measure each intersection degree of importance, considering the impact of other network intersections using GIS capabilities, dynamic traffic modeling and space syntax theory. Tests of each intersection degree of importance for a part of North-West of Tehran urban traffic network are conducted and the results verified the efficiency of the proposed method and support our strategy.

Faced with increasing congestion on urban roads, authorities need better real-time traffic information to manage traffic. Kalman Filters are efficient algorithms that can be adapted to track vehicles in urban traffic given noisy sensor data. A Kalman Filter process model that approximates dynamic vehicle behaviour is a reusable subsystem for modelling the dynamics of a multi-vehicle traffic system. The challenge is choosing the an appropriate process model that produces the smallest estimation errors. This paper provides a comparative analysis and evaluation of Linear and Unscented Kalman Filters process models for urban traffic applications.

Wireless Local Area Networks (WLANs) is one of the most promising access technologies for the upcoming fourth-generation wireless communication systems. In the last few years, several research efforts have been devoted to investigate possible multiple access schemes capable of supporting real-time traffic as well as best-effort data transmissions. In particular, the use of suitable transmission schemes allows not only to achieve higher data-rates, but also to perform resource allocation in order to guarantee specific service requirements. In this paper we propose a medium access control (MAC) scheme for a WLAN supporting realtime (voice) and best-effort (data) services, based on Orthogonal Frequency Division Multiplexing (OFDM) technique. A suitable analytical approach is proposed in order to derive the performance of the proposed MAC scheme. In particular, it is shown in the paper that a high overall network capacity in terms of simultaneously active users is achieved by effectively exploiting the multiuser capabilities offered by OFDM, together with a proper service differentiation.

Differentiated Services (DiffServ) architecture is based on aggregation of traffic and, unlike the Integrated Services (lntServ) the resources are not reserved on a per flow basis. One of the current research issues is the provision of Quality of Service (QoS) guarantees to real time traffic in the DiffServ environment. The idea here is to achieve these guarantees without per flow resource allocation while safeguarding the best effort traffic from extremely high delays. The self-similar nature of Internet traffic that results in burstiness and very high delays has been identified in the recent past. The problem at hand is, what packet-scheduling scheme can be used to minimise delay to reasonable limits and the levels of control to be applied on the aggregated traffic to achieve such limits. We propose a class based aggregated Priority Queue with Lower Real time Traffic Utilisation (PQ-LRTU) as a packet-scheduling scheme that is capable of providing statistical delay guarantees for DiffServ networks. Since only a real time traffic utilization threshold is maintained at the entrance to the network to control traffic, it provides a simple mechanism. Overall queue efficiency is achieved by using different levels of delay tolerable lower priority traffic.

Recent natural or man-made disasters around the world have provided compelling evidence that transportation system plays a crucial role in the emergency evacuation and have stressed the need for effective evacuation traffic management to maximize the utilization of the transportation system and to minimize fatalities and losses. This paper presents a model reference adaptive control ͑MRAC͒ framework for real-time traffic management under emergency evacuation. Distinct from the well-studied evacuation planning, real-time traffic management for evacuation aims to dynamically guide ͑control͒ traffic flow under evacuation in such a way that certain system objective ͑e.g., minimization of fatalities or property losses͒ could be achieved. The proposed framework is based on both dynamic network modeling techniques and adaptive control theory, by considering the traffic network under evacuation as a dynamic system. First, a prescriptive dynamic traffic assignment model is applied to predict, in a short-term and rolling-horizon manner, the desired traffic states based on certain system optimal objectives. This model will serve as a reference point for the adaptive control. Then, the adaptive control system integrates these desired states and the current prevailing traffic conditions collected via the sensing system to produce real-time traffic control schemes. Finally, these traffic control schemes are implemented in the field to guide the real-world traffic flow to evolve towards the desired states. Simulation studies provided in this paper show that the proposed framework based on MRAC can significantly improve the performance of real-time evacuation traffic management.

Most transit trip planning systems are based on static schedules and generate trips that do not dynamically respond to delays in transit operation caused by traffic congestion or accidents. In addition, the driving-parking-then-transit travel mode is common in metropolitan areas. However, very few transit trip planners incorporate real-time transit data into this mode. This article describes a multimodal trip planning system for multiple modes: driving, transit, and driving-parking-then-transit. The system considers the real-time transit arrival time, which is estimated by a prediction model. Both Web-based and mobile phone-based clients are used to access the system. Case studies show that the multimodal trip planning system works well in real-life situations.

1 -the European Union (EU) Framework Program 7 (FP7) funded project, iTETRIS [1] (An Integrated Wireless and Traffic Platform for Real-Time Road Traffic Management Solutions) targets to extend state of art in simulation of wireless vehicular cooperative systems for evaluation of road traffic management services and applications. In particular, iTETRIS addresses four important and distinct challenges: (a) road traffic and wireless integrated open-source simulation platform, (b) large scale trials, (c) realistic Vehicle to Vehicle (V2V) and Vehicle to Infrastructure (V2I) communication simulation and (d) dynamic, distributed and self-autonomous Intelligent Transport Systems (ITS) [2] applications based on cooperative systems. iTETRIS will provide a standard compliant, open-source integrated communication and traffic platform suited for large scale scenario simulation.

Differentiated Services (DiffServ) Architecture is based on aggregation of traffic as opposed to per flow traffic. When DiffServ is used in real time traffic environment it is important to study the effects of traffic aggregation on quality of service parameters. One-way delay and instantaneous packet delay variation (IPDV) are the most commonly used quality of service parameters for real time traffic. In this paper we study how one-way delay and IPDV are affected by traffic aggregation. We discover through our simulations and analytical models that IPDV remains unchanged with traffic aggregations as long as the micro flow granularity index (MFGI) is unchanged, while one-way delay is not affected purely due to aggregation. Further the IPDV of a given flow increases when the MFGI decreases for a given number of aggregated micro flows. We used a priority queue scheduler for our simulation where the real time traffic was served with highest priority.

SUMMARY This paper discusses the architecture of an Advanced Traveler’s Information System (ATIS), which uses the internet to disseminate real-time travel related information. The different parts of the system are integrated through the use of GIS (Geographic Information Systems) technologies. GIS can easily integrate data with a spatial dimension both for easy, intuitive access and improved visualization. Advances in the field of GIS have lead to the development of internet GIS, that is systems that provide full GIS functionality on the web. The system proposed is a web-based system. Real-time traffic dissemination is accomplished by linking the system to traffic monitoring systems, storing the information in databases and visualizing it on top of the actual street network. Information on location of activities can be provided from yellow pages databases and/or other available sources. Route alternatives can be estimated in realtime based on algorithms available in the system. User...

In this paper, a "real-time" traffic signal control strategy is provided using genetic algorithms to provide nearoptimal traffic performance for intersections. Real-time traffic signal control is an integral part of the urban traffic control system and providing effective real-time traffic signal control for a large complex traffic network is an extremely challenging distributed control problem. The developed "intelligent" system makes "real-time" decisions as to whether to extend green time for a set of signals. The model is developed using genetic algorithm implemented in MATLAB. A traffic emulator is developed in JAVA to represent dynamic traffic conditions. The emulator conducts surveillance after fixed interval of time and sends the data to genetic algorithm, which then provides optimum green time extensions and optimizes signal timings in real time. The optimization parameters are -total number of vehicles in a road and importance of the road in the intersection. In the end, by comparing the experimental result obtained by the fixed time and real time based traffic systems which improves significant performance for intersections, we confirmed the efficiency of our intelligent real time based control system.

In this paper, we discuss theoretical foundations and a practical realization of a real-time traffic sign detection, tracking and recognition system operating on board of a vehicle. In the proposed framework, a generic detector refinement procedure based on mean shift clustering is introduced. This technique is shown to improve the detection accuracy and reduce the number of false positives for a broad class of object detectors for which a soft response's confidence can be sensibly estimated. The track of an already established candidate is maintained over time using an instance-specific tracking function that encodes the relationship between a unique feature representation of the target object and the affine distortions it is subject to. We show that this function can be learned on-the-fly via regression from random transformations applied to the image of the object in known pose. Secondly, we demonstrate its capability of reconstructing the full-face view of a sign from substantial view angles. In the recognition stage, a concept of class similarity mea-Electronic supplementary material The online version of this article (sure learned from image pairs is discussed and its realization using SimBoost, a novel version of AdaBoost algorithm, is analyzed. Suitability of the proposed method for solving multi-class traffic sign classification problems is shown experimentally for different feature representations of an image. Overall performance of our system is evaluated based on a prototype C++ implementation. Illustrative output generated by this demo application is provided as a supplementary material attached to this paper.

... would be used to recalculate the signal timings and splits by consideration the signal parameters, such as minimum and maximum greens, permissive start and end times, and force-off green times. Development of Dynamic Transit Signal Priority Strategy Wael Ekeila, Tarek ...

Data gathering in a timely and reliable fashion has been a key concern in wireless sensor networks particularly related to military applications. The introduction of real time communication has created additional challenges in this area with different communication constraints. Since sensor networks represent a new generation of time-critical applications, it is often necessary for communication to meet real time constraints. However, research dealing with providing QoS guarantees for real time traffic in sensor networks is still immature. To provide guaranteed QoS in WSN, this paper presents a novel analytical model based on limited service polling discipline. The proposed model implements two queues in a sensor node which are being served according to round robin service. The model is based on M/D/l queueing system (a special class of M/G/l queueing systems), which takes into account two different classes of traffic in a sensor node. The exact queueing delay in a sensor node for corresponding classes is calculated. Further, the analytical results are validated through an extensive simulation study.

A new dynamic channel allocation scheme (DCAS) has been proposed for mobile satellite systems with the aim of improving the utilization of the network resources by reducing the handoff call dropping probability (HODP) while guaranteeing a certain quality of service for the new call blocking probability (NCBP). The arriving calls are given channels based on their priority. The handoff calls

This paper describes a prototype development of a new system for the integration of real-time traffic data within a GIS. Various functions of traffic monitoring systems are improved in terms of graphic capabilities in particular through the temporal visualisations of traffic conditions within an urban network. Traffic data are integrated and aggregated on a real-time basis. Complementary abstraction levels are used for both the spatial and temporal dimensions. Visualisations and animation tasks are developed using either spatial or thematical views

Bu Doktora tez çalışmamın sunumudur. Faydalanılması amacıyla paylaşıyorum. 25. Slaytta test sözlü olarak anlatılmıştır. Sonuçlar Ulaştırma Bakanlığı ile mail yoluyla paylaşılmıştı. Fakat bu mailimi bulamadım. Ulaştırma Bakanlığının Güncellenen Ulaşım ve İletişimde 2023 Hedeflerinin Karayolu Sektörü 2023 Hedefleri başlığı altında Trafik Yönetim Sistemi Merkezlerinin kurulması hedefi gecikmeli de olsa bu önerilerimin bazılarının dikkate alındığını gösteriyor. Eksik de olsa güzel bir gelişme.
Bu doktora tez çalışmasının amacı mobil sistemlerde gerçek zamanlı trafik bilgisi kullanarak alternatif araç güzergahlarının hesaplanması için yeni bir yaklaşım geliştirmek ve bu yaklaşımı coğrafi bir alanda uygulamaktır. Hemen her alanda teknolojik gelişmelerin çok hızlı yaşandığı, her geçen gün insanların hayatını kolaylaştıracak yeni buluşların, çözümlerin ve yaklaşımların olduğu bir yüzyıl yaşanmaktadır. İnsanoğlu karşılaştığı her problemin çözümü için her zaman pratik yöntemler arayışında olmuştur. Tüm bu buluşlar, çözümler ve yaklaşımlar farklı yönleriyle insanların karşılaştığı problemlere pratik çözümler sunmakta, ihtiyaçlarını gidererek hayatlarını kolaylaştırmakta, hızla akıp giden zamanı daha verimli kullanmalarını sağlamaktadır. Normalde çok uzun zaman alan işler, teknolojik gelişmelerin geldiği noktada getirdiği pratik çözümlerle çok kısa sürede bitirilebilmektedir. Günümüz dünyasında özellikle büyük şehirlerde insanların en çok şikâyetçi olduğu problemlerin başında trafik yoğunluğu gelmektedir. Bu durum, özellikle aracı olan ve bu trafiğe karışan her sürücü için çözülmesi gereken en önemli problemdir. Hiçbir sürücü, trafik yoğunluğu ve karmaşıklığının yaşandığı bir yolda zamanının boş yere geçmesini istemez. Bu açıdan, sürücüleri trafik yoğunluk ve karmaşasından kurtaracak alternatif çözümlerin geliştirilmesi çok büyük önem taşımaktadır. Bu tez çalışmasında, mobil sistemlerde gerçek zamanlı trafik bilgisi kullanarak alternatif araç güzergahlarının belirlenmesi amacıyla uygulama yazılımı geliştirilmiş ve coğrafi alan testleri yapılmıştır. Uygulama yazılımı C# platformunda geliştirilmiş olup, alternatif güzergah tespiti için Dijkstra algoritması kullanılmıştır. Klasik mobil navigasyon sistemlerinden farklı olarak, iki nokta arasındaki en uygun güzergahın sadece uzaklık bilgisi dikkate alınarak değil, çevrimiçi olarak sağlanan gerçek zamanlı trafik yoğunluğu bilgisinin de kullanılmasıyla belirlendiği uygulamalı bir çözüm sunulmaktadır. Bu sayede, tez çalışması kapsamında oluşturulması öngörülen Trafik İzleme ve Yönetim Merkezi (TİYM) tarafından sürücülere gerçek zamanlı olarak gönderilen trafik bilgileri ile önceden belirlenmiş olan güzergahın, oluşan yeni yol koşullarına bağlı olarak yeniden belirlenmesi sağlanmaktadır.

To the purpose of solving problems related to the transmission of multimedia contents on IP networks, several QoS models have been proposed, each of them with precise features. Till now, it looks clear that satisfactory quality performances can be obtained by combining different QoS models with some functionality provided by most advanced distributed multimedia applications. This work presents some experimental performance measures conducted on a testbed that reproduces an interoperability scenario where a VoD application runs on a dynamically configurable QoS network. Using this VoD application we were able to measure the network performances. The reference scenario is presented and both Premium IP Network and video streaming application are depicted.

Performance of a priority-based dynamic capacity allocation suitable for wireless ATM systems is presented. The scheduling of ATM cell transmission in each uplink TDMA frame is based on a priority scheme with priority given to real-time traffic over nonreal-time traffic. Real-time traffic exceeding the uplink capacity is lost while nonreal-time traffic that cannot be served is stored in a first-in first-out (FIFO) queue. An analytical model is developed to evaluate the cell loss ratio (CLR) of both real-time and nonreal-time traffic. Aggregate voice, video, and data traffic is modeled by three two-state Markov-modulated Poisson processes (MMPPs). Analytical results for different system capacities and various traffic loads and scenarios are discussed. Simulation results with on-off sources and approximating MMPP sources are also presented.

Providing Quality of Service (QoS) and Traffic Engineering (TE) capabilities in the internet is essential, especially in supporting the requirement of real-time traffic, as well as mission critical applications. Differentiated Services (DiffServ) is an emerging technology that provides QoS and traffic engineering features in Internet Protocol (IP) Network by programming the IXP2400 Intel Network Processor. Since the introduction of the network processors, there have been a number of network services developed based on the special-built, packet processing optimized programmable microprocessors. This paper is mainly concerns on how to deploy DiffServ in order to assess priority functionalities. A scheduling mechanism was developed on the IXP2400 network processor to provide QoS by maintaining priority of incoming packets based on criteria i.e. class of packets and traffic. The queuing mechanism improves the QoS of the traffic at the expense of some performance degradation. To reduce the performance degradation, a cache unit has been added into the operation of the QoS mechanism to cut down SRAM access during the lookup operation. A performance study was then carried out to evaluate the performance of the QoS mechanism after adding the cache unit. The overall speed is enhanced and delay is minimized. At the same time, the mechanism can be implemented on the ENP-2611 Evaluation Board to verify the functionality of the application on hardware.

IEEE 802.11 is a widely used standard for MAC and PHY layers of WLANs. Unfortunately, the access methods offered in this standard cannot support QoS (Quality of Service) for real-time traffics. Using multimedia applications over WLANs is increasing and, on the other hand, it seems that the access methods employed in this standard causes high variations in delay or jitter and wastes bandwidth due to collisions. There are many methods to enable DCFbasic access method in 802.11-with service differentiation and QoS. The difficulty in majority of these methods is unfair bandwidth allocation among low and high priority traffics at high loads resulting starvation for low priority traffics. In this paper, we modify the way that the CW (Contention Window) size is calculated after a successful transmission and study the effect of the CW size on performance and fairness. Results of our simulations show that the performance of DCF with this modification is better, specially, for traffics in which throughput is the most important parameter.

The paper summarizes experiences in the development of a real- time simulator which underlies the implementation of novel traffic information systems. The research project was carried out in collaboration between the Helsinki University of Technology (HUT)/ Laboratory of Transportation Engineering and the Nottingham Trent University (NTU)/ Department of Computing during a one year period from September 1997. The HUTSIM microscopic simulation model was interfaced to the SCOOT-urban traffic control system providing real-time traffic data through the Distributed Shared Memory system (DIME) developed at NTU. The emphasis of this paper is on presenting the principles of interfacing micro-simulation model to real-time field measurements, demonstrating a prototype implementation and outlining the range of information services that can be provided on the basis of such a system.

In this paper we explain why trivial solutions are inadequate for supporting deterministic QoS (quality of service) for real-time traffic in multi-hop ad-hoc networks with shared medium and contention based MAC (media access control) protocols. We also provide our initial work to address this issue with an analytical model within the context of suburban ad-hoc networks (SAHN). A SAHN is a multi-hop ad-hoc network. The analytical model is based on the channel access mechanism of a contention based MAC protocol such as the IEEE 802.11e. We refer to the improved IEEE 802.11e as SAHN-MAC. SAHN-MAC provides a distributed admission control and bandwidth reservation scheme by extending the features of IEEE 802.11e and coordinating with the network layer. The proposed admission control mechanism aims to prevent any new data stream from initiating if the new stream saturates or is about to saturate any part of the network. The bandwidth reservation scheme is necessary for the admission control scheme to work properly. These unique features make SAHN-MAC different from existing protocols. The proposed mechanisms have been verified via simulations.

We investigate the value of choosing the next stop to visit in a multistop trip based on current traffic conditions to minimize the expected total travel time of the tour. We model this problem as a Markov decision process. Numerical examples are presented that indicate that the value of using current traffic information for dynamic tour determination can be significant.

In this paper, we present the characteristics of a vehicular ad hoc network (VANET), which is the Shanghai urban vehicular network (SUVnet). We construct a mobility model using the GPS data collected from more than 4000 taxis in Shanghai. The model is both realistic and large scale. Based on this model, network topology and connectivity of SUVnet are studied. Because of the sparse distribution and dynamic topology of SUVnet, simply utilizing the conventional mobile ad hoc network routing protocols in SUVnet may not achieve a satisfactory performance. Therefore, we apply the delay-tolerant network model to SUVnet and evaluate the epidemic routing protocols. We propose a new protocol, which is the distance aware epidemic routing (DAER), to improve the bundle delivery ratio. Results show that DAER performs well for a VANET. This paper provides a basis in studying a realistic urban VANET.

There are several mobile work scenarios requiring real-time messages. Examples of these scenarios are disaster relief or mobile work in isolated areas. Although opportunistic networks are not intended for real-time messages, under certain conditions the communication could be feasible. This paper presents the schedulability analysis of an opportunistic network for real-time traffic. It includes a stochastic and deterministic analysis of the network performance. Moreover, a scheduling policy is also proposed.

IEEE 802.11 lacks of the capability to support quality of services such as multimedia and real-time traffic properly. This paper presents a simple approach to enhance the multimedia real-time performance over the 802.11 WLAN by implementing a Quality Of Service Manager (QoSM) for differentiating services with two queues on top of the 802.11 medium access controller. With slow decrease of

paper describes the prototype development of an inter-operable system for the integration of real-time traffic data within a GIS. The aim of our research project is twofold: (1) to improve current capabilities of traffic monitoring systems in terms of database functions, and (2) to explore analysis tools based on the visualisation and animation of traffic conditions within an urban network. The OSIRIS prototype objective is the integration and manipulation of historical traffic data within GIS, it complements current facilities of traffic monitoring systems. This paper presents the computing and geographical database environments of this inter-operable system. Traffic data are integrated and aggregated on a real-time basis. A pre-processor acts as a receiver of traffic data and as a data integrator for the traffic GIS application. Complementary abstraction levels are used for the spatial and temporal dimensions. Interactive visualisations and animation tasks are developed using either spatial or thematic views.