This paper presents data, collected from video-recording, on the microscopic details of merging and weaving manoeuvres under congested traffic conditions. Based on these observations, a ...classification of the manoeuvres into free, forced and cooperative lane changes is proposed. A new lane change model is developed, incorporating explicit modelling of vehicle interactions using intelligent agent concepts. The model was implemented in the ARTEMiS traffic simulator, and several hypothetical test studies were conducted to demonstrate the capabilities of the new model. The results show that the model is able to reproduce the observed behaviour of individual vehicles in terms of speed, gap acceptance and conflict-resolution in all three types of lane change manoeuvres, and hence, it is able to simulate highly congested flow conditions in a realistic manner. The macroscopic results in terms of speed-flow relationship are close to the typical expected results. The model can simulate both freeways and signalised urban arterial networks.
This paper introduces Simulation of Intelligent TRAnsport Systems (SITRAS), a massive multi-agent simulation system in which driver-vehicle objects are modelled as autonomous agents. The simulation ...outputs can be used for the evaluation of Intelligent Transport Systems applications such as congestion and incident management, public transport priority and dynamic route guidance. The model concepts and specifications, and the first applications of the model in the area of incident modelling in urban arterial networks were described in previous publications. This paper presents the details of the lane changing and merging algorithms developed for the SITRAS model. These models incorporate procedures for ‘forced’ and ‘co-operative’ lane changing which are essential for lane changing under congested (and incident-affected) traffic conditions. The paper describes the algorithms and presents simulation examples to demonstrate the effects of the implemented models. The results indicate that only the forced and cooperative lane changing models can produce realistic flow-speed relationships during congested conditions.
In this experimental study, the authors evaluated the biomechanical properties of the femoral press-fit graft fixation technique in ACL reconstruction. 20 fresh frozen distal femurs, patellae and ...patellar ligaments were used from 10 cadaver specimens. Three bone-patellar tendon grafts of 10 mm width were prepared from each sample; altogether 60 bone-patellar tendon grafts were prepared for the experiment. Three 9 mm wide tunnels were drilled in each distal femur at different angles (0, 15, 30, 45, and 60 degrees). This means that 60 tunnels were drilled into the 20 femurs, 12 at each angle. The trapezoid bone blocks were impacted into the holes. The primary stability and stiffness of this press-fit fixation method were measured with a Zwick 020 computer-controlled testing device using maximum-failure tensile-strength tests. The ultimate tensile strength was the greatest at 45 degrees (534+/-20 N, range 507-554), with 118+/-10 N/mm (range 99-126) stiffness, followed by 485+/-35 N (range 416-510) with 122+/-13 N/mm (range 104-136) stiffness at 30 degrees, 353+/-18 N (range 320-371) with 113+/-13 N/mm (range 83-124) stiffness at 15 degrees, and 312+/-30 N (range 261-343) with 89+/-14 N/mm (ranged:68-103) stiffness at 0 degrees. In the cases of 0, 15, 30 and 45 degrees the bone blocks were pulled out of the drilled holes, but at 60 degrees rupture of the patellar tendon or breakage of the bone block occurred more frequently. It can be seen that the ultimate tensile strength increased with the angle between the loading direction and the bone block. When compared to data in the literature, these data showed similar and satisfying biomechanical properties of femoral press-fit fixation. Because of the known advantages of an implantation-free fixation technique, the femoral press-fit fixation technique can be a good alternative in ACL surgery. These results provide the basis for future studies involving the postoperative healing process of this femoral press-fit fixation technique in porcine knees.
This paper presents findings from a comparative evaluation of car-following behaviour in a number of microscopic traffic simulators. The paper describes the results of the calibration and validation ...of the car following model implemented in the ARTEMiS simulator developed by the author. The calibration and validation are based on a ‘standard’ car-following experiment (called the Boschtest) which used instrumented vehicles to record the speed and relative distance between follower and leader vehicles on a one-lane road, and which was previously used to evaluate a number of other state-of-the-art simulators, including AIMSUN, PARAMICS and VISSIM. The simulated car following behaviour was compared to the field data using a number of error tests. A comparison of the results showed that the ARTEMiS car following model produced the closest match to the observed data out of all the tested models. In the last section of the paper, a number of traffic situations are identified where most car following models fail to reproduce real-life driver behaviour, and solutions to overcome these weaknesses are recommended for further development of car following models in microsimulation.
This paper reports the findings of a study aimed at testing and evaluating the lane changing and merging abilities, especially under congested flow conditions, of four traffic simulators: AIMSUN, ...ARTEMiS, PARAMICS and VISSIM. Several hypothetical traffic scenarios that require a large proportion of vehicles to merge and/or change lanes are constructed. These scenarios are then implemented in each model and simulated under increasing traffic flow rates. The model outputs are compared and evaluated and conclusions are drawn on the quality of the simulators in terms of their ability to model lane changing and merging in congested conditions. This paper describes the test scenarios, briefly introduces the parameters related to lane changing available in each simulator, presents the results of the simulation runs, summarises the findings and formulates recommendations for further research and model development.
The performance of the CMS Level-1 Trigger for supersymmetric events at an LHC luminosity of 2 x 1033 cm-2s-1 is reviewed. Energy and momentum trigger thresholds have been chosen to yield a maximum ...Level-1 output rate of 50 kHz, within a safety factor of three. The Level-1 trigger efficiencies for the majority of the channels studied are found to be greater than 90%, which provides a good basis for the High-Level Trigger, where more stringent conditions are applied. Reasons for occasional lower efficiencies are given.
Microscopic traffic simulation models are becoming increasingly important tools in modelling complex transport networks and evaluating various traffic management alternatives in order to determine ...the optimum solution for traffic problems that cannot be studied by other analytical methods. Several traffic simulation tools are used in Australia, especially PARAMICS, AIMSUN and VISSIM. While these packages have many similarities, each has its own specific characteristics that make it more or less suitable for certain modelling purposes. This paper is based on a study of the available documentation of the three models, a literature review and other information collected from the model users and developers; it evaluates and compares the functional capabilities, specific strengths and weaknesses, limitations and user opinions as at the time of writing (2004), and offers conclusions and recommendations on the suitability of each package for various modelling tasks.
We present our technique for surgically treating Tossy III acromioclavicular joint dislocation, discuss the indications for various procedures, and evaluate our postoperative results. We operated on ...17 patients suffering from chronic acromioclavicular instability after such dislocation using a modified Weaver-Dunn procedure, in which there is no lateral clavicular end resection, the coracoacromial ligament graft is sutured to the inferior part of the clavicle by transosseal sutures, and a Bosworth coracoclavicular screw is used to protect the graft postoperatively for 8 weeks. After a mean of 37 months we evaluated shoulder function by the Constant score and the subjective and radiological results. Mean Constant score was 91.9% (74-100%); it was 80-90% in 5 patients and above 90% in 11. One patient had screw loosing after the operation and suffered partial loss of reduction and discomfort during shoulder loading. All patients but one returned to work, and all but one have returned to their preoperative activity at the same level. Subjectively, there were 11 excellent and 6 good results. Compared to the contralateral uninjured side, radiography showed anatomical reposition in the vertical plane in 9 cases, slight loss of reduction in 6 (difference in the distance between the inferior border of the acromion and the clavicle is 2-4 mm), and partial loss of reduction in 2 (4-8 mm). We recommend the modified Weaver-Dunn procedure for surgical treatment of chronic, Tossy grade III acromioclavicular joint dislocations as it provides good functional and subjective results. Our modification is indicated mainly for young patients because posttraumatic arthrosis occurs more frequently in elderly patients, making clavicular end resection necessary.
PDF
