How Roundabout Entry Design Parameters Influence Safety

Novák, Jan; Ambros, Jiří; Frič, Jindřich

doi:10.1177/0361198118776159

Cited by 16 publications

(11 citation statements)

References 27 publications

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“…According to their findings, the frequency of crashes tended to rise with increase in the traffic volume and inscribed circle diameter. Novák et al (2018) found that entry design parameters significantly influence safety in terms of crash frequency and speeds at the roundabout, especially at the approach level. Similarly, Al-Marafi et al (2020) considered traffic and geometric features and their influences on the safety performance of roundabouts.…”

Section: Literature Reviewmentioning

confidence: 99%

Safety evaluation of urban roundabouts in India: a safety performance function-based approach

Vinayaraj

Vedagiri

2022

TSR

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There is a lack of comprehensive research in roundabout safety under non-lane-based traffic conditions, mainly due to the absence of relevant crash data and effective tools for safety evaluation. Safety Performance Function (SPF) is a suitable tool for providing valuable information related to factors which can potentially contribute to the likelihood of increasing traffic crashes. Currently, very limited studies are available to explain the usefulness of SPF in the vicinity of roundabouts, especially at non-lane-based traffic conditions. This study aims to develop an SPF model for assessing the safety evaluation at roundabouts as a whole (intersection level) and the approach level. Data corresponding to crashes in nineteen roundabouts with different geometric and traffic characteristics was used for model formulation. Crash data for five years (2015–2019) was obtained from the State Crime Records Bureau. An SPF model was developed using a negative binomial model with a log-link function based on the number of crashes, traffic characteristics, and geometry characteristics of the roundabouts. The proportion of powered two-wheelers, percentage of heavy vehicles, entry-angle, and weaving-length were all significantly related with higher crash occurrences at roundabouts, according to the findings. In contrast, the number of circulatory lanes, inscribed circle diameter, and presence of road lane marking were negatively associated with the increased crash occurrences at the roundabout vicinity. In addition to this, the overall crash rate significantly varies across roundabout sections due to the asymmetric effects of geometric and traffic characteristics. The developed SPF would best explain the relationship between geometric and traffic characteristics and the crash occurrence rate in non-lane traffic conditions. The findings of this study support the need to relook at design parameters for better movement at the roundabouts, thereby improving the existing facilities to enhance road users' safety, especially in developing countries. The proposed SPF tool would help engineers examine the safety of roundabouts in terms of design adequacy, quantifying the risk factors, and future crash predictions.

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Section: Literature Reviewmentioning

confidence: 99%

Safety evaluation of urban roundabouts in India: a safety performance function-based approach

Vinayaraj

Vedagiri

2022

TSR

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“…Crash prediction models were used by various researchers to explain the safety aspects at various levels based on the influence of geometric and traffic characteristics (6,15,(25)(26)(27)(28)(29)(30)(31)(32). The variables considered are radius at entry, the width of entry, angle to next leg, central island diameter, entry path radius, average annual daily traffic, number of approaches, and circulating lane number.…”

Section: Crash Prediction Modelsmentioning

confidence: 99%

“…Furthermore, the crash frequency of segments can be predicted by using various regression methods such as negative binomial ( 20 ), multiple logistic ( 21 ), and zero-inflated negative binomial ( 22 ). In addition to this, some researchers ( 6 , 23–26 ) have suggested that Poisson and negative binomial models can be a better model for predicting the discrete, rare, and non-negative crash count. Though the above models are widely used for modeling the crash count at various transportation facilities, there are limited studies that modeled roundabouts safety using these models.…”

Section: Research Backgroundmentioning

confidence: 99%

Developing Safety Performance Functions and Crash Modification Factors for Urban Roundabouts in Heterogeneous Non-Lane-Based Traffic Conditions

Vinayaraj

Vedagiri

2023

Transportation Research Record: Journal of the Transportation R

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This study aims to develop safety performance functions (SPFs) and crash modification factors (CMFs) for the safety assessment of roundabouts as a whole and their components, especially at entry, exit, and circulating lanes. This study uses historical crash data collected over five years (2015–2019) from 21 roundabouts (78 approaches) situated in some of the major cities in India. SPF and CMF models were developed using negative binomial and cross-sectional approaches. Results show that the percentage of motorized two-wheelers, average daily traffic, central island diameter, entry angle, weaving width, departure width, number of lanes at approach, exit angle, exit width, posted speed limit, weaving length, circulating roadway width, road surface condition, number of circulatory lanes, central island height, and number of legs contribute to the crash occurrence in the roundabout vicinity. In addition to this, circulating roadway width, average daily traffic, and posted speed limit are the most influencing risk factors across the entire roundabout vicinity. Furthermore, an interesting fact is that, given the asymmetrical impact of geometric and traffic factors, the overall crash rate varies across roundabout segments. The findings of this study may be useful for updating the current design guidelines for roundabouts, considering the safety perceptive. Besides, the proposed SPF and CMF tools could be used to investigate the likelihood of crashes at roundabouts. Moreover, this model would help safety experts to implement adequate safety treatment in the vicinity of roundabouts under heterogenous non-lane-based traffic conditions.

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“…Ulusal ve uluslararası trafik kaza kayıtlarına bakıldığında kavşak noktalarının potansiyel risk taşıdığı görülmektedir. Yapılmış olan istatiksel çalışmalar Amerika Birleşik Devletleri'nde ölümlü ve yaralanmalı kazaların %50'sinden fazlasının, Avrupa ülkelerinde ise trafik kazalarının ortalama %27'si ve ölümlü kazaların ortalama %10'unun kavşaklarda meydana geldiğini göstermektedir [5][6][7]. Ülkemiz karayolu ulaşım ağında ölümle, yaralanmayla veya maddi hasarla sonuçlanan trafik kazalarına ait veriler incelendiğinde, kazaların %50'sinin şehir içi, %30'unun ise şehirlerarası kavşaklarda meydana geldiği görülmektedir [8].…”

Section: Gi̇ri̇ş (Introduction)unclassified

Dönel Kavşak Geometrik Elemanlarının Kavşak Güvenliği Üzerine Etkisinin Literatür Işığında Değerlendirilmesi

Özinal

2021

Politeknik Dergisi

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Ulaşım sistemi içerisindeki trafik akımının güvenli ve etkin biçimde işlemesi üzerinde büyük rolü bulunan kavşaklar, faaliyet alanı, geometrik özellikleri ve denetim şekillerine göre farklı kategorilere ayrılmaktadır. Kontrollü eş düzey kavşak kategorisindeki dönel kavşaklar, trafik akımının merkezi ada etrafında yönlendirildiği ve ada içerisindeki araçların ilk geçiş hakkına sahip olduğu kavşak tipidir. Dönel kavşakların her bir geometrik elemanı kavşağın işleyiş, kapasite ve güvenliği üzerinde rol oynamaktadır. İyi tasarlanmış bir dönel kavşak, araçların dolaşım yolu boyunca hızlarının sabit kalmasını sağlayarak kavşak güvenliğinin optimize edilmesine yardımcı olur. Bu makalede, dönel kavşakların geometrik elemanlarının kavşak güvenliği üzerine etkilerinin incelendiği çalışmalar derlenmiştir. Dönel kavşakların her bir geometrik elemanın literatürde yer alan çalışmalar ışığında kavşak güvenliğiyle olan ilişkileri ve bazı ülkelerin standart/kılavuzlarında yer alan tasarım kriterleri incelenmiştir. Bu çalışmayla amaçlanan, yapılmış çalışmalar doğrultusunda, dönel kavşak geometrik elemanlarının tasarımlarının kavşak güvenliği açısından hayati önem taşıdığını ortaya koymaktır. Ülkemizde bu konuyla ilgili olarak daha önce yapılmış detaylı çalışmalara rastlanılmaması çalışmamızın motivasyon kaynağı olmuştur. Ülkemizdeki dönel kavşakların hangi standart/kılavuzlara bağlı olarak yapıldığı ile ilgili bilgi yetersizliği olduğu da görülmektedir. Çalışma sonucunda dönel kavşaklardaki güvenliğin sağlanabilmesi için geometrik elemanların birbirleriyle etkileşim içinde ve uygun fiziki boyutlarda tasarlanması gerektiği belirtilmiştir. Ayrıca trafik güvenliği bakımından ülkemizde bu konuyla ilgili ivedilikle çalışmalara başlanılması ve ülkemiz koşullarına özgü tasarım standart/kılavuzu hazırlanması gerektiği ifade edilmiştir.

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How Roundabout Entry Design Parameters Influence Safety

Cited by 16 publications

References 27 publications

Safety evaluation of urban roundabouts in India: a safety performance function-based approach

Safety evaluation of urban roundabouts in India: a safety performance function-based approach

Developing Safety Performance Functions and Crash Modification Factors for Urban Roundabouts in Heterogeneous Non-Lane-Based Traffic Conditions

Dönel Kavşak Geometrik Elemanlarının Kavşak Güvenliği Üzerine Etkisinin Literatür Işığında Değerlendirilmesi

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