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1

An impact of gap acceptance on road safety: A critical systematic review

Bhatt Khushbu, Shah Jiten

Journal of Sustainable Development of Transport and Logistics

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2022

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Vol. 7, No. 1

6--22

EN

An uncontrolled intersection is a critical area for crashes that depends on macroscopic traffic parameters. While the intersection is the potential of the center of crashes due to inappropriate decision of driver. Therefore, the study focuses on the effect of the gap acceptance parameter for the safety of drivers at an uncontrolled intersection. To examine, a systematic review of the literature is implemented to understand the different parameters, their impact, and models developed by the researchers. Additionally, it is demonstrated that the crashes are highly affected by the gap acceptance and the different models are formed to estimate the critical gap for different road sections under homogeneous and heterogeneous traffic conditions. However, it is not possible to definitively conclude the best model to evaluate the gap acceptance factor but can be preferred to reduce the severity of crashes. Nonetheless, most studies remain inconclusive, there is an emerging trend in the literature suggesting the increase of the crash risk at an uncontrolled intersection. Lastly, it is most important to mention the model suitability based on empirical studies commenced under the strong limitations. Consequently, there is a need for research in this area to correlate the gap acceptance with road safety to reduce the severity of accidents to improve the existing transportation system.

2

Practical aspects of measuring critical gaps and follow-up times at median uncontrolled T-intersections

Barchański Adrian, Żochowska Renata

Zeszyty Naukowe. Transport / Politechnika Śląska

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2021

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z. 113

17--28

EN

Estimation of critical gaps and follow-up times between vehicles at uncontrolled intersections is an essential step in estimating the capacity of these objects and assessment of traffic conditions. Therefore, measurements of these parameters should be properly prepared and implemented. This paper presents issues related to the performance of field tests at median uncontrolled T-intersection. Measurements included both critical gaps and follow-up times. Based on the collected material, the authors identified problems occurring during traffic observation. Analyzed intersections were located both within and outside built-up areas. Furthermore, this article discusses the influence of selected factors on the accuracy of estimating the critical gaps and follow-up times and formulates the principles of conducting traffic measurements at selected types of intersections.

3

Estimation of critical gaps and follow-up times at median uncontrolled T-intersection

Barchański Adrian, Żochowska Renata

Archives of Transport

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2021

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Vol. 60, iss. 4

105--124

EN

The efficiency of the entire transportation system depends on the capacity of the individual elements that make up the given network. Point-type elements of the road and street network include intersections of different types. Critical gaps and follow-up times related to individual movements are important determinants of the capacity of such objects. There are many ways to estimate such times. The article discusses the assumptions and scheme one of them - the Siegloch method. The objective of the article is to analyze the process of determining critical gaps and follow-up times at the median uncontrolled T-intersections that are rare in the road and street network and have been studied to a limited extent. The commonly used HCM, HBS, and Polish (MOP SBS) methods in their current form do not consider the specificity of such intersections and thus may not give reliable results. Due to their characteristics in terms of geometry conditions, there is a need for an individual approach to estimate both critical gaps and follow-up times. The article contains the results of empirical research conducted on a selected real object in the Upper Silesian agglomeration in Poland. The intersection under study is located in one of the central districts of Katowice city, in the built-up area serving commercial and service functions. The analysis of the behavior of individual drivers waiting for the possibility to continue driving was conducted separately for each minor traffic movement. The values of critical gaps and follow-up times were determined for all four subordinate movements. The values obtained are different from those contained in the Polish manual, which is recommended for use. The research should be considered as pilot studies that justify the need to develop a separate approach to the estimation of the critical gaps and follow-up times at median uncontrolled T-intersections.

4

Assessment of psychotechnical parameters of vehicle drivers on roundabout Hitachi Taga, Japan

Macioszek Elżbieta, Kang Nan

Zeszyty Naukowe. Transport / Politechnika Śląska

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2019

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z. 103

93--103

EN

The assessment of psychotechnical parameters (that is, critical gaps and follow-up times) of vehicle drivers at roundabout Hitachi Taga, Ibaraki Prefecture in Japan was presented in this paper. The basis for this assessment were empirical data from measurements in the field, made in two different years. The first field measurement took place two years after the construction of the roundabout in 2014, and the second one in 2019. The results comparison of 2014 and 2019 was aimed at assessing possible changes in the psychotechnical parameters in time. This assessment was carried out as one of the element of the project titled “Analysis of the applicability of the author's method of roundabouts entry capacity calculation developed for the conditions prevailing in Poland to the conditions prevailing at roundabouts in Tokyo (Japan) and in the Tokyo surroundings”, financed by the Polish National Agency for Academic Exchange.

5

Effect of Vehicle Composition and Delay on Roundabout Capacity under Mixed Traffic Conditions

Abhigna D., Kondreddy S., Ravi Shankar K. V. R.

Archives of Transport

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2016

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Vol. 40, iss. 4

7--14

EN

Roundabouts are replacing conventional unsignalized intersections in many parts of the world (Polus and Shmueli, 1997). Capacity estimation is necessary for designing a new roundabout, to analyze and improve the existing roundabout facilities. There are several methods to estimate the capacity of the roundabout, but most of them are for homogeneous lane based traffic conditions and not applicable for mixed traffic conditions. This study tries to find out the applicability of the existing methods to mixed traffic conditions, identify the effect of vehicle composition, travel time and delay on capacity. In this study, data was collected from two roundabouts located in Mysore, Karnataka and Rajahmundry, Andhra Pradesh in India. Capacities for both the roundabouts are calculated using the existing methods and compared. VISSIM simulation model has been developed and analyzed for different vehicle compositions scenarios. It was observed that vehicle composition of the traffic influences the roundabout capacity. Since the entry capacity of a roundabout varies significantly with the vehicle composition of the traffic at the roundabout, it is necessary to incorporate this factor into the existing capacity estimation models.

6

Performance of roundabouts

Chodur J.

Archives of Civil Engineering

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2009

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Vol. 55, nr 4

467-485

EN

As small roundabouts are becoming an increasingly popular type of at-grade intersections, researchers are encouraged to study new computational methods and carry out comprehensive studies of roundabout performance. A series of empirical studies of capacity of small roundabout entries have helped to produce models for estimating the basic capacity parameters. Carried out in a number of Polish cities, the work was instrumental in adjusting the known models to local conditions and in calibrating the theoretical capacity model of small roundabout entry based on the theory of gap-acceptance. The paper also presents model of capacity of the right-turn bypass used on several Polish roundabouts, carrying large volumes of right-turn movements. In assessing the performance of an intersection, identifying its capability of carrying the largest hourly volumes at peak times is not enough. Because traffic volumes vary, intersections are considered efficient not only if they operate to the required capacity, but if they also have a relatively low sensitivity to variable traffic loads, and a sufficient capacity to meet variable volumes of arriving traffic flows. The objective of the studies was to identify the sensitivity of small roundabouts to variable daily traffic volumes, looking at changes in volume, composition of traffic flow movements on intersecting roads, and directional composition of flows at roundabout entries. One of the results of the study is that if the share of turning movements (right and left) on roundabout entries increases, the range of capacity differences becomes smaller and causes the differences of vehicular delay of major and minor traffic go up. Roundabouts that can efficiently handle a broad range of variable traffic streams (variable volumes and directional composition), become less sensitive to possible traffic estimation errors or failed traffic flow predictions than major/minor priority intersections.

PL

Częste stosowanie małego ronda, jako rozwiązania skrzyżowań drogowych z jednej strony skłania a z drugiej umożliwia podejmowanie badań zmierzających do uaktualniania metod obliczeniowych oraz prowadzenia wszechstronnych analiz ich sprawności. Przeprowadzone w wielu miastach w Polsce empiryczne badania przepustowości wlotów podporządkowanych małych rond umożliwiły opracowanie dostosowanych do warunków lokalnych modeli estymacji podstawowych parametrów determinujących przepustowość a także umożliwiły kalibrację teoretycznego modelu przepustowości wlotu ronda (jednopasowego, dwupasowego i semi-dwupasowego) opartego na teorii akceptacji luk czasowych. W pracy przedstawiono również model przepustowości włączenia bypasa, stosowanego często na polskich rondach z dużymi natężeniami relacji skrętu w prawo. W ocenie sprawności skrzyżowania niewystarczające jest określenie zdolności przenoszenia największych natężeń godzinowych, występujących w szczytowych okresach ruchu. W czasie eksploatacji rondo poddawane jest zmiennym obciążeniom ruchem. Za sprawne rozwiązanie skrzyżowania uznać można takie, które nie tylko ma wystarczającą przepustowość, ale cechuje się także relatywnie małą wrażliwością na zmiany natężeń ruchu, czyli zapewnia wymagane warunki ruchu w dość szerokim zakresie zmienności dopływających potoków ruchu. Podjęte badania miały na celu określenie wrażliwości małego ronda na dzienne wahania natężenia ruchu, obejmujące zmiany wielkości natężenia, rozkładu kierunkowego ruchu na krzyżujących się drogach oraz struktury kierunkowej na wlotach ronda. Badania wykazały np., że wraz ze wzrostem udziału relacji skrętnych (w lewo i w prawo) na wlotach ronda maleje przedział różnic przepustowości a rosną różnice strat czasu pojazdów pomiędzy dominującym i drugorzędnym kierunkiem. Sprawność ronda w szerokim zakresie zmienności przepływających strumieni ruchu (zmienność wielkości natężeń oraz struktury kierunkowej) czyni to skrzyżowanie mniej wrażliwym niż skrzyżowanie z pierwszeństwem przejazdu na ewentualne błędy estymacji istniejących bądź nieścisłości prognoz przyszłych danych ruchowych.

7

Zastosowanie wykresu siła-przemieszczenie w próbie Charpy V do analizy odporności na pękanie w temperaturze ciekłego azotu, technicznie czystego żelaza

Wawszczak J.

Problemy Eksploatacji

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2007

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nr 4

249-263

PL

W pracy rozważano metodę wyznaczania dynamicznego współczynnika odporności na pękanie KId. Koncepcję oparto na wykorzystaniu krzywych siła-przemieszczenie, uzyskanych w trakcie próby udarności Charpy V. Wartości przemieszczenia w punkcie przyłożenia siły w przebiegu próby udarności Charpy V określano na próbkach z żelaza czystego technicznie w temperaturze ciekłego azotu. Określano położenie punktu krytycznego na krzywej dopasowania przemieszczenia względem rzeczywistej wartości ugięcia próbki. Wyniki dynamicznej odporności na pękanie porównano względem próbek, w których karb technologiczny przedłużono o pęknię-cie uzyskane metodami zmęczeniowymi.

EN

The method of the fracture resistance coefficient KId, determination was introduced in this paper. This idea is based on the curve's force-displacement, obtained during Charpy V impact tests. Displacement values at the point of the force application in relation to the time were measured during impact tests. The impact resistance of the commercially pure iron Charpy V samples were performed at the temperature of liquid nitrogen. The critical point initiation on the fit curve of displacement versus original deflection was indicated. The results of dynamic fracture resistance values were compared with the results of resistance coefficients from samples with initiative crack, performed with fatigue crack tips at the ends of technological notches.