1,721,150 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Dynamic behavioural data collection using an instrumented vehicle
No full textA significant problem that has become increasingly apparent in the development of models of driver behavior over the last few years is the absence of reliable data with which simulated processes, such as car following, may be compared. Obtaining such data, and the associated increase in model validity that this would allow, is clearly becoming of greater importance since a reliable baseline is required against which improvements in traffic flow and safety produced by many advanced transport telematics systems can be judged. One source of such data is an instrumented vehicle: a vehicle equipped with relative distance- and speed-measuring sensors that may be deployed in the traffic stream to collect data that are realistic, accurate, and dynamic. The opportunities for data collection afforded by instrumented vehicles are examined, in particular, the construction and testing of a new facility fitted with an optical speedometer, a radar rangefinder (capable of measuring the distance to, and relative speed of, the next vehicle in the traffic stream), and forward- and rear-looking video cameras. Examples are given of the use of the vehicle in several current research projects, the operational strategies for which will be presented and discussed along with output. These include experiments on close-following, lane-changing, and the perception of relative speed. In conclusion, future areas of research and development are examined.<br/
Drivers' use of deceleration and acceleration information in car-following process
No full textUnderstanding driver behavior is important for the development of many applications such as microscopic traffic simulation models and advanced driver assistance systems. The car-following process is an important phase of driving behavior and takes place when a driver follows a lead vehicle and tries to maintain distance and relative speed within an acceptable range. A key to improving knowledge of driver behavior during this process is determining the information perceived by drivers that could influence their decisions. It has been believed for some time that the main kinematic parameters that affect driver judgment in car following are the relative speed, the distance separation, and the absolute speed. The research described investigated whether drivers are also able to use information on the lead vehicle's deceleration or acceleration during the car-following process through experimental validation of current car-following hypotheses. For this research, an instrumented vehicle was used to collect a large database of car-following time sequences, the analysis of which showed strong evidence that drivers are able to perceive information such as the deceleration or acceleration of the vehicle being followed, although no empirical relationship was determined. An example demonstrating the importance of such perception shows that modeling a driver trying to avoid a collision with a lead vehicle would lose 20% of its fit accuracy if the lead-vehicle acceleration state were not considered
Coordinating on-ramp queue control with adjacent local signal controller: an algorithm to assist ramp metering application
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