The Stopping Sight Distance Test for Freeway Based on the Operating Speed

2011 ◽  
Vol 97-98 ◽  
pp. 180-184
Author(s):  
Yue Zhang
Keyword(s):  
Safety Evaluation ◽  
Operating Speed ◽  
Horizontal Curve ◽  
Passenger Car ◽  
Sight Distance ◽  
Stopping Sight Distance

In this paper, the stopping sight distance of passenger car based on the operating speed was regarded as guideposts, and its corresponding radius of horizontal curve and vertical curve was got according to the calculated results, and available for reference and application in the alignment design and safety evaluation for freeway.

Sight distance red zones on combined horizontal and sag vertical curves

1998 ◽  
Vol 25 (4) ◽  
pp. 621-630 ◽  
Author(s):  
Yasser Hassan ◽  
Said M Easa
Keyword(s):  
Quantitative Analysis ◽  
Three Dimensional ◽  
The Other ◽  
Two Dimensional ◽  
Horizontal Curve ◽  
Sight Distance ◽  
Stopping Sight Distance ◽  
Three Dimensional Models ◽  
Highway Alignment ◽  
Current Standards

Coordination of highway horizontal and vertical alignments is based on subjective guidelines in current standards. This paper presents a quantitative analysis of coordinating horizontal and sag vertical curves that are designed using two-dimensional standards. The locations where a horizontal curve should not be positioned relative to a sag vertical curve (called red zones) are identified. In the red zone, the available sight distance (computed using three-dimensional models) is less than the required sight distance. Two types of red zones, based on stopping sight distance (SSD) and preview sight distance (PVSD), are examined. The SSD red zone corresponds to the locations where an overlap between a horizontal curve and a sag vertical curve should be avoided because the three-dimensional sight distance will be less than the required SSD. The PVSD red zone corresponds to the locations where a horizontal curve should not start because drivers will not be able to perceive it and safely react to it. The SSD red zones exist for practical highway alignment parameters, and therefore designers should check the alignments for potential SSD red zones. The range of SSD red zones was found to depend on the different alignment parameters, especially the superelevation rate. On the other hand, the results showed that the PVSD red zones exist only for large values of the required PVSD, and therefore this type of red zones is not critical. This paper should be of particular interest to the highway designers and professionals concerned with highway safety.Key words: sight distance, red zone, combined alignment.

Safety Evaluation for the Highway Alignment with 3D Visual Simulation

2012 ◽  
Vol 182-183 ◽  
pp. 1131-1134
Author(s):  
Xiao Jia Chen ◽  
Yi Cheng Luo
Keyword(s):  
Safety Evaluation ◽  
Visual Simulation ◽  
Horizontal Curve ◽  
Current Standard ◽  
Highway Design ◽  
Standard Requirement ◽  
Sight Distance ◽  
Real Scene ◽  
A Minor ◽  
Highway Alignment

In the current highway design, poor coordinate of the alignment has a great effect on the sight distance which would increase the danger and difficulty of driving. For this reason, safety checking for highway alignment is required by the current standard. In this paper, 3D simulation technique was used to model the real scene of driving. Based on the concept of the preview sight distance (PVSD), two typical coordinates of alignment in practice were discussed. Although the current standard requirement is met, it is demonstrated that the alignment in the location of a minor horizontal curve and combination of a tangent with a circular curve could still provide driver confusing information. Some recommendations were suggested so as to improve the highway alignment design.

Operating Speed on Crest Vertical Curves with Limited Stopping Sight Distance

2000 ◽  
Vol 1701 (1) ◽  
pp. 25-31 ◽  
Author(s):  
Daniel B. Fambro ◽  
Kay Fitzpatrick ◽  
Charles W. Russell
Keyword(s):  
Operating Speed ◽  
Design Elements ◽  
Geometric Data ◽  
A Value ◽  
Sight Distance ◽  
The Mean ◽  
The Difference ◽  
Design Speed ◽  
Stopping Sight Distance ◽  
The Relationship

Horizontal and vertical elements of a highway are designed based on an assumed design speed. This concept was developed in the 1930s as a mechanism for designing rural alignments to permit most drivers to operate uniformly at their desired speed. In 1938, AASHO recognized that drivers select a speed influenced by the roadway environment instead of an assumed design speed. Recent research suggests that design speed is no longer the speed adopted by the faster group of drivers but that it has become a value used to establish the sharpness of horizontal and vertical design elements. The objective of this study was to establish the relationship between design and operating speeds for crest vertical curves with limited sight distance. Geometric data and 3,500 paired speeds (speeds at control and crest sections) were collected at 36 sites in 3 states. The results indicated that both the 85th percentile and the mean operating speeds were well above the inferred design speeds of the crest vertical curves for the range of conditions studied and that the lower the design speed the larger the difference between the 85th percentile speed and the design speed. The mean reductions in speed between the control and crest sections tend to increase as available sight distance is decreased; however, the reduction in speed is less than that suggested by current AASHTO criteria.

Three-Dimensional, Probabilistic Highway Design

2008 ◽  
Vol 2060 (1) ◽  
pp. 10-18 ◽  
Author(s):  
Mohamed Sarhan ◽  
Yasser Hassan
Keyword(s):  
Reliability Analysis ◽  
Probabilistic Approach ◽  
Three Dimensional ◽  
Design Parameters ◽  
Horizontal Curve ◽  
Vertical Alignment ◽  
Highway Design ◽  
Side Slope ◽  
Sight Distance ◽  
Stopping Sight Distance

The potential usefulness of reliability analysis has recently been stressed in many engineering applications. Given the variability in the design parameters, a reliability-based probabilistic approach is well suited to replace the current deterministic highway design practice. However, progress in this regard is generally slow. In this study, the reliability analysis was used to estimate the probability of hazard (POH) that might result from insufficiency of sight distances. As an application, the available sight distance was checked against required stopping sight distance on an assumed road segment. Variation of the design parameters was addressed with Monte Carlo simulation using 100,000 sets of design parameters based on distributions available in the literature. A computer program was developed to use these sets of design parameters to calculate the profiles of available and required stopping sight distances in two- and three-dimensional projections as well as the profile of POH. The approach was applied to a horizontal curve overlapping with flat grade, crest curves, and sag curves in a cut section where the side slope would restrict the sightline. The analysis showed that the current deterministic approach yields very conservative estimates of available and required stopping sight distance, resulting in very low POH. The application example also showed the change of POH with the change of vertical alignment parameters.

Reliability Analysis for Roadway Curves with Horizontal Sightline Obstructions

2019 ◽  
Vol 2673 (8) ◽  
pp. 611-622 ◽  
Author(s):  
Daniel J. Cook ◽  
Douglas W. Harwood ◽  
Ingrid B. Potts ◽  
Eric T. Donnell ◽  
Bachir Hamadeh
Keyword(s):  
Reliability Analysis ◽  
Three Dimensions ◽  
Crash Analysis ◽  
Horizontal Curve ◽  
Analysis Model ◽  
Flexible Tool ◽  
Horizontal Curves ◽  
A Value ◽  
Sight Distance ◽  
Stopping Sight Distance

Objects on the inside of a horizontal curve may limit the stopping sight distance (SSD) available to drivers. Crash analysis shows that SSD-related crashes on horizontal curves are limited in number and difficult to quantify. As an alternative, a reliability analysis model was developed to quantify the number of drivers per year who may encounter a stopped vehicle in a sight-restricted area, creating an opportunity where an SSD-related crash might occur on a roadway with a sight obstruction on the inside of a horizontal curve. The model considers roadway alignment in three dimensions. The model formulation is documented and an analysis of the sensitivity of crash opportunities to traffic volume and offset to a sight obstruction is performed. A sensitivity analysis of the reliability analysis model shows that the percentage of vehicles that may encounter a crash-involved vehicle or a queue of stopped vehicles over the course of a year can range from essentially zero to a value approaching 1% of the total yearly flow. The reliability analysis model is a flexible tool that can be used by planners and designers to compare, in a relative sense, the need for sight distance improvements on specific horizontal curves.

scholarly journals Effects of vegetation type and horizontal curve radius on the rate of tree pruning to provide line of sight on main access roads

2014 ◽  
Vol 60 (No. 5) ◽  
pp. 208-211
Author(s):  
M. Nasiri ◽  
M.R. Pourmajidian
Keyword(s):  
Vegetation Type ◽  
Line Of Sight ◽  
Horizontal Curve ◽  
Horizontal Curves ◽  
Sight Distance ◽  
Hardwood Trees ◽  
Significant Difference ◽  
Stopping Sight Distance ◽  
Curve Radius ◽  
Tree Pruning

The present investigation was carried out to assess the influence of vegetation type and horizontal curve radius on the rate of tree pruning to provide the line of sight on horizontal curves in Caspian forests of Iran. For this purpose, the DBH (diameter at breast height) of trees around the curves which must be pruned was measured. Also, the horizontal curves radius was divided into 4 classes and for each class 10 horizontal curves (for each species) were selected and the species which required pruning were measured. The rate of radial pruning was determined to provide a minimum stopping sight distance by means of laser rangefinder along the line of sight. We found an inverse relationship between DBH and the rate of pruning. To provide sight vision, the radial pruning rate decreased regularly with the increasing radius of horizontal curves for coniferous species, while it increased irregularly for broadleaves. There was a significant difference in pruning between different radii of horizontal curves (P < 0.05). According to results, pruning should be done for mixed hardwood trees with widespread crowns and no sharp horizontal curves should be designed at the top or bottom of hills.  

Driver Eye and Vehicle Heights for Use in Geometric Design

1998 ◽  
Vol 1612 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Kay Fitzpatrick ◽  
Torsten Lienau ◽  
Daniel B. Fambro
Keyword(s):  
Geometric Design ◽  
Design Criteria ◽  
Passenger Cars ◽  
Passenger Car ◽  
Sight Distance ◽  
Total Vehicle ◽  
Vehicle Fleet ◽  
Stopping Sight Distance

Driver eye, headlight, taillight, and vehicle heights are important elements for determining passing and intersection sight distances and horizontal and vertical curve lengths to provide required stopping sight distance. Driver eye and object heights have varied significantly since their inception in the 1920s, when their values were suggested as 1676 mm. The objective of this study was to determine appropriate driver eye, headlight, taillight, and vehicle heights for use in developing geometric design criteria. The results of this research were used to recommend a driver eye height of 1080 mm for design purposes. This value represents 90 percent of the passenger car driver eye height values and an even higher percentage of the total vehicle fleet, because passenger cars have the lowest driver eye height values and represent fewer than two-thirds of the total vehicle fleet. Headlight and taillight heights of 600 mm are recommended for design. These values represent over 90 and 95 percent of the passenger cars observed in this study, respectively. The vehicle height recommendation for sight distance was 1315 mm, which represents the 10th percentile passenger car height values measured in the research.

Traffic and speed characteristics on two-lane highways: field study

2003 ◽  
Vol 30 (6) ◽  
pp. 1042-1054 ◽  
Author(s):  
Yasser Hassan
Keyword(s):  
Light Condition ◽  
Operating Speed ◽  
Ambient Light ◽  
Horizontal Curve ◽  
Vehicle Class ◽  
Rural Highways ◽  
Horizontal Alignment ◽  
Heavy Truck ◽  
Traffic Composition ◽  
Rural Highway

Many models have been developed to evaluate the operating speeds on two-lane rural highways. However, provided information usually lacks details essential to assess their applicability at locations other than where they were developed. This paper presents a procedure to interpret raw data collected on three horizontal curve sites of different two-lane rural highway classes in Ontario. The speed observations were categorized into three vehicle classes (passenger car, light truck, and multi-axle heavy truck) and four light condition categories (day, night, and two transition periods). The minimum headway and percentile value to define the operating speed were examined, and a revision of the current practice deemed not warranted. The findings also indicated that operating speeds do not depend on the time or vehicle class. Finally, the horizontal alignment affects the operating speed, but the speeds of the two travel directions on a horizontal curve may differ even with little contribution of the vertical alignment.Key words: highway geometric design, operating speed, traffic composition, traffic counters, ambient light, acceleration, deceleration.

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