Showing papers on "Collision avoidance published in 1974"

Patterns of Public Behaviour: Collision Avoidance on a Pedestrian Crossing

Abstract: One of the more remarkable aspects of public life in cities is the phenomenon of pedestrian routing. On almost any street corner one may daily witness large numbers of people navigating their courses along the pavements without bumping into each other. What is especially interesting about this complex avoidance behaviour is the apparent ease with which it is effected. Yet it is performed in the absence of an explicit code and with few, if any, individuals being able to specify the procedures whereby they and other people avoid collisions. Despite the everyday nature of pedestrian avoidance behaviour, and the important questions which it raises concerning interpersonal coordination, the phenomenon has not, at least until very recently, received the attention it deserves. Recent investigations in this area have looked at behaviour on pavements. Most of these studies have proceeded from the observation of

Some Aspects of Collision Avoidance

Abstract: S aspects of the problem of collision avoidance for two chicles are examined by hypothesizing certain rationales for the vehicle operators and then computing the sets of initial conditions for which collision can occur. We first suppose that one operator may be unaware of any danger and so may control his vehicle in a hazardous fashion. To this operator we assign the role of pursuer, while the operator of the other vehicle is given the role of evader and a differential game is formulated. The set of initial conditions for which collision can occur despite any maneuvers by the evader is a dangerous (Red) zone. Clearly, a cautious pilot would not like a second vehicle to be in his Red zone, and a good collision avoidance system (CAS) should be effective in this zone. A second zone is defined by assigning a passive role (constant control) to the evader, while the other vehicle still pursues. The set of initial conditions for which no collision is possible is a particularly safe zone since no active avoidance is required. Any practical CAS should not call for unnecessary maneuvers in the (Green) zone. The points in neither the Red nor the Green zones form a Yellow zone in which some evasive maneuver may be required. A workable CAS should be active for initial points in the Yellow zone, so that the Red zone can be avoided.

The effects of sensor errors in certain marine collision avoidance and threat assessment systems

Abstract: The paper distinguishes between optimal and practical collision avoidance systems and selects a set of variables that can be used to compute collision avoidance (C/A) parameters in practical systems. Specifically, the paper studies the effects of sensor errors upon the calculation of the passing distance at CPA, the point-of-possible-collision (PPC), and range over range-rate (TAU). The possible sources of error are summarized and characterized as deterministic or random, dependent or independent, correlated or decorrelated, and fixed bias. A computer program is described that makes use of a Kalman filter to compute the effects of error upon C/A parameters. The results of computer runs are given that show that most errors have insignificant effects. The others can be reduced or removed if required. A means is provided for estimating a part of the economic return on investment in a computerized collision avoidance system.

Collision avoidance radar braking systems investigation: phase i study

Abstract: The feasibility of an automotive radar braking system suitable for installation on all U.S. automobiles as standard equipment was investigated on the basis of utilizing state-of-the-art technology and demonstrating cost-effective performance in terms of preventing accidents otherwise caused by inattentive or tardy driver response. A technology survey identified several radar brake system concepts existing in demonstrable hardware and capable of automatically responding to and avoiding impact with obstacles on a collision course. To assess the cost-effectiveness of radar brakes, four generalized baseline systems were defined: Automatic/noncooperative; automatic/cooperative; semi-automatic/noncooperative; semi-automatic/cooperative. These four system types were then considered in regard to their effectiveness in preventing accidents of certain categories judged responsive to their respective performance capabilities.

Probability of Collision in a Model Collision Avoidance System

Abstract: A basic concept for estimating the probability of collision for a ship navigating through a seaway with congested marine traffic can be derived by applying queuing theory to the relation between collision evoidance manoeuvres and the traffic environment. Ships usually perform various 'services', such as altering course of collision avoidance, to other ships and geographical obstacles; the analogy of the collision avoidance system to queuing is that each arrival of another ship represents a 'customer' and each manoeuvre of own ship corresponds to a 'service'. A model for a collision-avoidance system was constructed analytically from queuing theory and expressed numerically, under assumptions based on traffic surveys and the statistical analysis of collision avoidance procedures at sea, in order to study the feasibilities of the model. The calculated probabilities of collision for ships in Japanese straits were compared with the collision statistics over the last five years and agreement was good except for low values of collision probability. They were also found to correspond well with the psychological evaluations of more than one thousand navigators as to the mental strain due to the traffic environment in each strait. Based on the model, factors which influence the risk of collision were quantitatively investigated.

Automated collision avoidance - a new look at an old problem -

Abstract: The Merchant Marine has for some time needed an Automated Collision Avoidance System. The advent of this equipment could herald startling changes in bridge operation. However, one is forced to remember that at one time the relative motion unstabilized radar was heralded as a boon to the Maritime Industry in the form of a tool to reduce, if not eliminate collisions at sea. While we eagerly await the time when all ships are equipped with ACAS, we also recognize the need for maintaining--in fact, increasing--the skill of the Deck Officer to make collision avoidance assessments. These questions must be asked: What happens when he is forced to fall back on his standby system? When all ships are ACAS equipped, will we now have a new generation of problems where a Deck Officer using the trial maneuver mode decides on a safe maneuver in a complex grouping of ships, maneuvers and finds himself now forced to make yet another decision? How do we prepare these men to make use of the information displayed? We must recognize that though the equipment is automated and displays tremendous quantities of informations, it still requires the final closing of the system loop by a decision from the Deck Officer. This paper treats these and other questions and proposes changes in time honored techniques of plotting and maneuvering by Radar. These changes will adequately compensate for the occasion when a malfunction reduces the automated system to its basic component. This study has been underway for approximately two years. The Deck Officers, who will ultimately be responsible for the proper operation of any ACAS, have been involved as test subjects. Even though this work has covered a wide range of considerations in the area of collision avoidance, there are many areas still under study.

Landing rates for mixed STOL and CTOL traffic

Abstract: A study was made to determine the expected landing rate for STOL-only traffic and mixed STOL-CTOL traffic. The conditions used vary from present day standards to an optimistic estimate of possible 1985 conditions. A computer program was used to determine the maximum landing rate for the specified conditions and aircraft mix. The results show that the addition of STOL on a CTOL runway increases the total landing rate if the STOL airborne spacing can be reduced by use of improved navigation equipment. Further, if both takeoff and landings are performed on the same runway, the addition of STOL traffic will allow an increase in the total operation rate, even with existing spacing requirements.

Collision Avoidance Ground Station Analysis

Abstract: : Three different collision avoidance system (CAS) analyses were performed; ground station clock requirement, Loran-C accuracy and comparisons, and CAS monitoring requirements. Cesium beam standards are evaluated to determine their time accuracy, the number required to attain and maintain time to within 0.5 microseconds, 3 sigma. The Loran-C system is reviewed to determine the potential time accuracy attainable by monitoring the Loran-C transmission. The results are then compared to the accuracy attainable from satellite, television, WWV and WWVB time transfer. The CAS equipment has certain built-in tests. These tests, as well as additional external monitors, are reviewed to categorize the test type and effectiveness.