Passing sight distance on two-lane highways: Review and revision

Hassan, Yasser; Easa, Said M.; Halim, A O Abd El

doi:10.1016/0965-8564(95)00032-1

Cited by 44 publications

(108 citation statements)

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“…A value of α=1would mean that the maneuver is already completed. The assumption of critical point at α=0.5 was similar to other models (10,11), and was necessary since the observation of aborted maneuvers was very unusual (observed 3 aborted and 1,098 completed).…”

Section: Psd Modelmentioning

confidence: 99%

“…Using a combination of video, GPS and laser rangefinder data, following variables were measured ( The length of passing and impeding vehicle Li and Lp were obtained after identifying its brand and model. The selection of the previous variables followed previous research studies (9)(10)(11)(12)(13)(14)(15). These variables provided information about passing duration, passing speeds and distance traveled during passing.…”

Section: Data Collectionmentioning

confidence: 99%

“…This model was selected among a variety of assumptions in the literature, such as uniform speed (6), or uniform speed from critical point (10,11). Alternative models were also evaluated, such as acceleration linear functions of time or speed.…”

Section: Psd Modelmentioning

confidence: 99%

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Sight Distance Standards Based on Observational Data Risk Evaluation of Passing

Llorca

Moreno

Sayed

et al. 2014

Transportation Research Record

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This paper presents an application of reliability analysis for evaluating the risk associated with passing sight distance standards in terms of expected probability of noncompliance.The calculation of passing sight distance (PSD) is required to determine where drivers can safely execute passing maneuvers. Traditional PSD standards are based on deterministic, theoretical models, which are calibrated using conservative percentiles values for uncertain design inputs to account for uncertainty. They do not provide information about the risk of deviating from them. Reliability analysis is a technique based on limit state design that accounts for the propagation of variability from input random parameters to the design outputs.A total of 1,098 passing maneuvers were observed on several two-lane highways in Spain, using two different data collection methodologies: external observations and instrumented vehicle. The most significant factors affecting PSD were: impeding vehicle speed, passing vehicle acceleration, and headways between impeding and passing vehicles. A uniform acceleration model described passing vehicle trajectory. The characterized input parameters and the passing model were used to perform a reliability analysis. The results showed the probability of noncompliance in different scenarios, defined as the proportion of cases where the required PSD would exceed the available sight distance.American and Spanish PSD standards were evaluated. Geometric design standards presented a probability of noncompliance of about 0.15, while some of the marking standards had probability of noncompliance exceeding 0.85. These standards may be associated with higher risk levels if they were followed by drivers. As well, PSD risk levels were not consistent for different design speeds, since they underestimate operating speed at some locations. Llorca et al., 2014 3 INTRODUCTION Several researchers have noted that existing design guides provide a deterministic approach for

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Section: Psd Modelmentioning

confidence: 99%

Section: Data Collectionmentioning

confidence: 99%

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Sight Distance Standards Based on Observational Data Risk Evaluation of Passing

Llorca

Moreno

Sayed

et al. 2014

Transportation Research Record

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“…At crest curves, steep grades cause inadequate sight distance that could impair safety. Over the past two decades, a number of researchers have established explicit relationships between highway vertical grade and safety, including Easa [7,8], Hassan and Easa [9], and Labi [10,11]. Other noteworthy contributors include Hassan et al [12][13][14] who discussed the importance of sight distance and operating speed along with combined horizontal and vertical alignments at highway cut and fill sections.…”

Section: Introductionmentioning

confidence: 99%

Highway Design and Safety Consequences: A Case Study of Interstate Highway Vertical Grades

Tang

Chen

Cheng

et al. 2018

Journal of Advanced Transportation

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Vertical alignment, which includes vertical grades and lengths, is a critical aspect of highway design policy that influences safety. A full understanding of the effect of vertical grade and segment length on highway safety can help agencies to evaluate or adjust their design policies regarding vertical alignment design features (grade and length). For this reason, it is useful to assess the current relationships between design policy and safety performance. To address this task, this paper uses data from interstate segments to first establish the relationship between these design features and safety. Safety is expressed in terms of the three different levels of crash severity (fatal, injury, and property damage only). In its analysis, the paper departs from the traditional univariate models (where each crash severity is modeled separately) and instead uses a seemingly unrelated negative binomial (SUNB) technique, a multivariate model that duly accounts for the unobserved shared effects between the different levels of crash severity. In addition, the paper's models duly recognize and account for the holistic nature of the grade and tangent length effects: the effect of the sum (interaction) of the vertical grade and length is different from the sum of their individual effects. The paper investigates the relationships for rural and urban interstate highway segments. Against the background of the developed models, the paper evaluates current design policies (specifications on vertical alignment grade and length) for similar classes of highways at a number of countries and presents a set of nomograms that feature lines representing points of equal safety performance. These charts can be used by the highway agencies to evaluate and compare their current or possible future highway design policies.

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“…Table 1 provides minimum passing zone lengths from the geometric design and marking standards for Spain (2, 3) and the US (4)(5)(6). Generally, the values come from deterministic approaches (7,8), where risk has not been taken into account and conservative percentiles of variables have been selected. In general, passing zone criteria define a minimum passing sight distance that must available to allow passing.…”

Section: Introductionmentioning

confidence: 99%

Design Criteria for Minimum Passing Zone Lengths

Moreno

Llorca

Lenorzer³

et al. 2015

Transportation Research Record

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Passing zones are provided to improve operational efficiency of two-lane highways where passes can be performed safely. Minimum passing zone lengths of 120 m were established in MUTCD and Green Book, although some studies indicate a potential need to increase them. However, no changes have been recommended pending further research on the safety of short passing zones.The objective of this study is to develop design and marking criteria for minimum passing zone lengths that consider traffic operational efficiency and safety.In the first part of this study, a traffic microsimulation was carried out with Aimsun software. The calibration and validation included the observation of 1,750 passing maneuvers in Spain. The results indicate that passing zones shorter than 250 m add very little to operational efficiency. In the second part of the study, a reliability analysis was applied. It quantified the probability that a passing maneuver was completed beyond the end of the passing zone (noncompliant passing maneuvers). Afterwards, the number of non-compliant passing maneuvers was calculated. Traffic flow as well as passing zone length were contributing factors..Findings from the analysis indicate that the minimum passing zone length should be increased to a minimum of 275 m, for high traffic volumes, 300 m for medium traffic volumes and 350 m for low traffic volumes. From this length, the number of non-compliant passing maneuvers decreases. The marginal increase in the minimum length of passing zones can potentially improve safety without significantly reducing the operational efficiency. The results can be directly used by practitioners to establish the minimum passing zone length based on the range of hourly volumes and the level of risk willing to assume.

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Passing sight distance on two-lane highways: Review and revision

Cited by 44 publications

References 1 publication

Sight Distance Standards Based on Observational Data Risk Evaluation of Passing

Sight Distance Standards Based on Observational Data Risk Evaluation of Passing

Highway Design and Safety Consequences: A Case Study of Interstate Highway Vertical Grades

Design Criteria for Minimum Passing Zone Lengths

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