Current Issue : October - December Volume : 2011 Issue Number : 4 Articles : 7 Articles
Recent development in connected vehicle technology or equivalently vehicular ad hoc networks (VANET) has stimulated tremendous interests among decision makers, practitioners, and researchers due to the potential safety and mobility benefits provided by these technologies. A primary concern regarding the deployment of connected vehicle technology is the degree of market penetration required for effectiveness. This paper proposes a methodology to analyze the benefit of highway capacity gained from connected vehicle technology. To fulfill this purpose, a model incorporating the effects of connected vehicle technology on car following is formulated, building on which a rough estimate of the resulting capacity gain is derived. A simulation study is conducted to verify the model, and an illustrative example is provided to show the application of the methodology. This work provides decision makers and practitioners with a basic tool to understand the mobility benefit obtained from connected vehicle technology and how such benefit varies as market penetration changes....
Vehicular networks are the major ingredients of the envisioned Intelligent Transportation Systems (ITS) concept. An important component of ITS which is currently attracting wider research focus is road traffic monitoring. The actual approaches for traffic road monitoring are characterized by longer response times and are also subject to higher processing requirements and possess high deployment costs. In this paper, we propose a completely distributed and scalable mechanism for wireless sensor network-based road traffic monitoring. The approach relies on the distributed and bidirectional exchange of traffic information between the vehicles traversing the routes and a miniature cluster head and takes into consideration both the security and reliability of data communication. In addition, the communication between nodes is collision-free since the underlined data link layer protocol relies on a heuristic time multiplexed-based protocol. The performance analysis shows that the proposed mechanism usually outperforms other algorithms for different traffic densities....
Today's advanced simulators facilitate thorough studies on Vehicular Ad hoc NETworks (VANETs). However the choice of the physical layer model in such simulators is a crucial issue that impacts the results. A solution to this challenge might be found with a hybrid model. In this paper, we propose a semi-deterministic channel propagation model for VANETs called UM-CRT. It is based on CRT (Communication Ray Tracer) and SCMEââ?¬â?UM (Spatial Channel Model Extendedââ?¬â?Urban Micro) which are, respectively, a deterministic channel simulator and a statistical channel model. It uses a process which adjusts the statistical model using relevant parameters obtained from the deterministic simulator. To evaluate realistic VANET transmissions, we have integrated our hybrid model in fully compliant 802.11?p and 802.11?n physical layers. This framework is then used with the NS-2 network simulator. Our simulation results show that UM-CRT is adapted for VANETs simulations in urban areas as it gives a good approximation of realistic channel propagation mechanisms while improving significantly simulation time....
This paper presents a comparative study of outer rotor PMAC machine candidates for starter-generator application in hybrid bus with series power train configuration. PMAC machines with interior and surface mount permanent magnets are considered and compared, although a complete analysis is only carried out for the SPM. Different design aspects such as concentrated versus distributed windings as well as interior and exterior rotor structures are evaluated. Different slot numbers per pole per phase configurations for concentrated winding PMAC machines are also examined. Comparison and evaluation of the machines is based on their performance which included evaluation of winding and iron losses, magnet losses, and maximum torque capability as well as the size and weight of the machines....
The implementation of ITS (Intelligent Transport Systems) services offers great potential to improve the level of safety, efficiency and comfort on our roads. Although cooperative traffic safety applications rely heavily on the support for real-time communication, the Medium Access Control (MAC) mechanism proposed for the upcoming IEEE 802.11p standard, intended for ITS applications, does not offer deterministic real-time support, that is, the access delay to the common radio channel is not upper bounded. To address this problem, we present a framework for a vehicle-to-infrastructure-based (V2I) communication solution extending IEEE 802.11p by introducing a collision-free MAC phase assigning each vehicle an individual priority based on its geographical position, its proximity to potential hazards and the overall road traffic density. Our solution is able to guarantee the timely treatment of safety-critical data, while minimizing the required length of this real-time MAC phase and freeing bandwidth for best-effort services (targeting improved driving comfort and traffic efficiency). Furthermore, we target fast connection setup, associating a passing vehicle to an RSU (Road Side Unit), and proactive handover between widely spaced RSUs. Our real-time MAC concept is evaluated analytically and by simulation based on a realistic task set from a V2I highway merge assistance scenario....
Considering automatic and effective stereo image matching for vehicle-borne mobile mapping system (VMMS), a new stereo image matching algorithm based on digital parallax model (DPM) is proposed in this paper. The new matching propagation strategy is designed in this algorithm, which includes two processes as DPM construction and parallax prediction. With some known matched points, the DPM of stereo image pairs is firstly constructed, and parameters for confirming conjugate epipolar line is also worked out. Then searching range during dense matching can be confirmed under constraints of DPM and epipolar line, which can improve matching speed and accuracy. Furthermore, to improve matching robustness, the computation model of similarity measurement combined with local structure feature and global color feature is designed. The new algorithm is applied to actual stereo images taken by VMMS to verify its validity. Experimental results show that the proposed approach has higher reliability and accuracy....
Road traffic microsimulations based on the individual motion of all the involved vehicles are now recognized as an important tool to describe, understand, and manage road traffic. Cellular automata (CA) are very efficient way to implement vehicle motion. CA is a methodology that uses a discrete space to represent the state of each element of a domain, and this state can be changed according to a transition rule. The well-known cellular automaton Nasch model with modified cell size and variable acceleration rate is extended to two-lane cellular automaton model for traffic flow. A set of state rules is applied to provide lane-changing maneuvers. S-t-s rule given in the BJH model which describes the behavior of jammed vehicle is implemented in the present model and effect of variability in traffic flow on lane-changing behavior is studied. Flow rate between the single-lane road and two-lane road where vehicles change the lane in order to avoid the collision is also compared under the influence of s-t-s rule and braking rule. Using results of numerical simulations, we analyzed the fundamental diagram of traffic flow and show that s-t-s probability has more effect than braking probability on lane-changing maneuver....
Loading....