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Wyszukujesz frazę "sight distance" wg kryterium: Temat


Wyświetlanie 1-3 z 3
Tytuł:
Empirical modeling of the relationship between decision sight distance and stopping sight distance based on AASHTO
Autorzy:
Bassan, S.
Powiązania:
https://bibliotekanauki.pl/articles/224006.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
sight distance
stopping
maneuver
speed
deceleration
decision
odległość
zatrzymanie
manewr
prędkość
zmniejszenie prędkości
Opis:
The paper introduces implementation of highways' stopping sight distance (SSD) and decision sight distance (DSD) based on AASHTO modeling assumptions. SSD characterizes the necessary distance for highway vehicles to stop safely in front from an obstacle. SSD is a function of vehicle speed, perception reaction time, deceleration rate, and grade based on AASHTO and most highway design international guidelines. The deceleration rate which is assumed constant (3.4 m/sec2) based on AASHTO 2011 is generally controlled by the friction coefficient depending on the road surface conditions. A driver's demanded deceleration rate may not exceed the range of friction coefficient according to various pavement conditions. Although SSD is generally sufficient to allow skilled and alert drivers to the stop their vehicles under regular situations, this distance is insufficient when information is difficult to comprehend. A DSD should be provided in highways geometric design when the driver is required to detect an unexpected or difficult to perceive information source. Interchanges (specifically exit ramps) and intersections, and required changing in driver direction of travel, changes in the basic cross section such as toll plaza, lane drop, are typical scenarios where driver needs DSD in the safety manner. The introduction of the two sight distance types (SSD and DSD) is a perquisite for empirical modeling of the relationship between DSD and SSD. The modeling refers to DSD for rural highways, suburban roads, and urban roads based on AASHTO models. Specifically the paper covers DSD three avoidance maneuver types of stopping (types A, A1, B) and three maneuver types of speed, path, and direction changing (types C,D, E) for the three roadway categories. The major parameters that control these avoidance types are pre-maneuver times, and pre-maneuver plus maneuver times. The empirical relationship proposed in this study simplifies the process of evaluating the decision sight distance based on stopping sight distance record, based on AASHTO models, without the need of strenuous estimation of the DSD model maneuver and deceleration parameters. Such a simplified correlation has not been found in the literature except a rough approximation documented in the British highway design guidelines.
Źródło:
Archives of Transport; 2018, 48, 4; 7-25
0866-9546
2300-8830
Pojawia się w:
Archives of Transport
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sight distances at unsignalized intersections: a comparison of guidelines and requirements for human drivers and autonomous vehicles
Autorzy:
Magyari, Zsofia
Koren, Csaba
Kieć, Mariusz
Borsos, Attila
Powiązania:
https://bibliotekanauki.pl/articles/1955153.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
intersection
sight distance
autonomous vehicle
speed
gap acceptance
skrzyżowanie nieoznaczone
odległość widzenia
pojazd autonomiczny
prędkość
Opis:
Many traffic accidents are caused by unforeseen and unexpected events in a site that was hidden from the driver's eyes. Road design parameters determining required visibility are based on relationships formulated decades ago. It is worth reviewing them from time to time in the light of technological developments. In this paper, sight distances for stopping and crossing situations are studied in relation to the assumed visual abilities of autonomous vehicles. Current sight distance requirements at unsignalized intersections are based among others on speeds on the major road and on accepted gaps by human drivers entering or crossing from the minor road. Since these requirements vary from country to country, regulations and sight terms of a few selected countries are compared in this study. From the comparison it is remarkable that although the two concepts, i.e. gap acceptance on the minor road and stopping on the major road have different back-grounds, but their outcome in terms of required sight distances are similar. Both distances are depending on speed on the major road: gap sight distances show a linear, while stopping sight distances a parabolic function. In general, European SSD values are quite similar to each other. However, the US and Australian guidelines based on gap acceptance criteria recommend higher sight distances. Human capabilities and limitations are considered in sight field requirements. Autonomous vehicles survey their environment with sensors which are different from the human vision in terms of identifying objects, estimating distances or speeds of other vehicles. This paper compares current sight field requirements based on conventional vehicles and those required for autonomous vehicles. Visibility requirements were defined by three vision indicators: distance, angle of view and resolution abilities of autonomous cars and human drivers. These indicators were calculated separately for autonomous vehicles and human drivers for various speeds on the main road and for intersections with 90° and 60° angles. It was shown that the required sight distances are 10 to 40 meters shorter for autonomous vehicles than for conventional ones.
Źródło:
Archives of Transport; 2021, 59, 3; 7-19
0866-9546
2300-8830
Pojawia się w:
Archives of Transport
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Elements of perfect order rate research in logistics chains
Autorzy:
Jacyna-Gołda, Ilona
Kłodawski, Michał
Lewczuk, Konrad
Łajszczak, Marcin
Chojnacki, Tomasz
Siedlecka-Wójcikowska, Teresa
Powiązania:
https://bibliotekanauki.pl/articles/223482.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
sight distance
decision
stopping
maneuver
speed
deceleration
logistics chains
order rate research
ocena stanu zamówienia
łańcuch logistyczny
Opis:
Perfect order rate (POR) is one of the superior measures of the logistics processes quality. POR is at the top of the hierarchy of key performance indicators (KPI) in supply chain and is considered as difficult to define and measure. Perfect order rate is composed of sub-measures touching technical, economic, quality and safety aspects of logistics processes. POR directly defines what the organization considers to be the perfect implementation of its tasks (and thus sets goals for the organization) and, secondly, measures the degree of achievement of these goals. The paper defines the concept of perfect order rate by including new elements to classic definition, so far rarely considered in the literature: possibility of order implementation according to standard procedures in organization and safety aspects. The concept of logistics chain and the impact of its functioning on the POR value have been defined. The picking and replenishment processes were discussed in detail as the basic elements affecting the quality of logistics processes and the value of POR. Next, the issues of logistic processes safety in warehouse facilities were discussed. The large intensity of warehouse operations along with their mechanization and automation very often leads to many hazards in warehouses and logistics chain. These hazard are usually related with warehouse workers safety. However, they can also lead to various delays or downtime in the material flows, as well as damage or reducing the quality of materials. So it was assumed that safety aspects can influencing the value of POR in the logistics chain. Due to conducted research and compiled reports indicate that many accidents in the warehouse are associated with the forklifts use as equipment for material handling. Therefore, in paper main attention was paid to hazards related with forklifts, warehouse safety speed, etc.
Źródło:
Archives of Transport; 2019, 49, 1; 25-35
0866-9546
2300-8830
Pojawia się w:
Archives of Transport
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-3 z 3

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