B.M.R. Heijligers

Heavily used urban networks remain a challenge for travel time prediction because traffic flow is rarely homogeneous and is also subject to a wide variety of disturbances. Various models, some of which use traffic flow theory and some of which are data driven, have been developed to predict traffic flow and travel times. Many of these perform well under set conditions. However, few perform well under all or even most urban traffic conditions. As part of the Amsterdam Practical Trial, a… Show more

Heavily used urban networks remain a challenge for travel time prediction because traffic flow is rarely homogeneous and is also subject to a wide variety of disturbances. Various models, some of which use traffic flow theory and some of which are data driven, have been developed to predict traffic flow and travel times. Many of these perform well under set conditions. However, few perform well under all or even most urban traffic conditions. As part of the Amsterdam Practical Trial, a comprehensive field operation test for traffic management, a real-time travel time prediction framework, was developed to make use of an ensemble of traffic modeling techniques to predict travel times with great accuracy for arterial roads as well as urban roads. The various models in the framework include both traffic theoretical models and data-driven approaches, making use of some of the largest real-time traffic data sets currently available to limit errors to less than 20% for any time of day or week. The impending implementation of the framework sets it at the forefront of practical real-time implementation of urban travel time prediction. Show less

The design and implementation of the Road Side Unit for the A270 Test Site is presented. It consists of a sensor platform and V2I communication platform with full coverage of the test site. A service platform enables applications to make use of these facilities. The RSU will be used both for the implementation of real-time cooperative applications, and for independent testing and evaluating of cooperative ITS systems. It has been developed as part of the Dutch project SPITS. KEYWORDS road side… Show more

The design and implementation of the Road Side Unit for the A270 Test Site is presented. It consists of a sensor platform and V2I communication platform with full coverage of the test site. A service platform enables applications to make use of these facilities. The RSU will be used both for the implementation of real-time cooperative applications, and for independent testing and evaluating of cooperative ITS systems. It has been developed as part of the Dutch project SPITS. KEYWORDS road side unit, V2I communication, video based monitoring, test site, cooperative systems INTRODUCTION Show less

Active galactic nuclei (AGNs) display many energetic phenomena—broad emission lines, X-rays, relativistic jets, radio lobes—originating from matter falling onto a supermassive black hole. It is widely accepted that orientation effects play a major role in explaining the observational appearance of AGNs. Seen from certain directions, circum-nuclear dust clouds would block our view of the central powerhouse1,2. Indirect evidence suggests that the dust clouds form a parsec-sized torus-shaped… Show more

Active galactic nuclei (AGNs) display many energetic phenomena—broad emission lines, X-rays, relativistic jets, radio lobes—originating from matter falling onto a supermassive black hole. It is widely accepted that orientation effects play a major role in explaining the observational appearance of AGNs. Seen from certain directions, circum-nuclear dust clouds would block our view of the central powerhouse1,2. Indirect evidence suggests that the dust clouds form a parsec-sized torus-shaped distribution. This explanation, however, remains unproved, as even the largest telescopes have not been able to resolve the dust structures. Here we report interferometric mid-infrared observations that spatially resolve these structures in the galaxy NGC 1068. The observations reveal warm (320 K) dust in a structure 2.1 parsec thick and 3.4 parsec in diameter, surrounding a smaller hot structure. As such a configuration of dust clouds would collapse in a time much shorter than the active phase of the AGN3, this observation requires a continual input of kinetic energy to the cloud system from a source coexistent with the AGN. Show less