Improved Design of Vertical Curves with Sight Distance Profiles

2003 ◽  
Vol 1851 (1) ◽  
pp. 13-24 ◽  
Author(s):  
Yasser Hassan
Keyword(s):  
Design Procedure ◽  
The United States ◽  
Analytical Models ◽  
Minimum Length ◽  
Vertical Alignment ◽  
The Road ◽  
Sight Distance ◽  
Special Cases ◽  
Current Design ◽  
Improved Design

Design of vertical alignment is one of the main tasks in highway geometric design. This task requires, among other things, that the designer ensure drivers always have a clear view of the road so they can stop before hitting an unexpected object in the road. Therefore, the ability to determine the required and available stopping sight distance (SSD) at any point of the vertical alignment is essential for the design process. Current design guides in the United States and Canada provide simple analytical models for determining the minimum length of a vertical curve that would satisfy the sight distance requirement. However, these models ignore the effect of grade on the required SSD. Alternative approaches and models have also been suggested but cover only special cases of vertical curves. Two specific models were expanded to determine the required SSD on crest and sag vertical curves. By comparing profiles of available SSD and required SSD on examples of vertical curves, it was shown that current North American design practices might yield segments of the vertical curve where the driver’s view is constrained to a distance shorter than the required SSD. An alternative design procedure based on the models was developed and used to determine the minimum lengths of crest and sag vertical curves. Depending on the approach grade, these new values of minimum curve length might be greater than or less than values obtained through conventional design procedures. Design aids were therefore provided in tabular form for designers’ easy and quick use.

Mathematical Models of Vehicular Speed on Mountain Roads

2000 ◽  
Vol 1701 (1) ◽  
pp. 104-110 ◽  
Author(s):  
Pedro Jose Andueza
Keyword(s):  
Mathematical Models ◽  
Design Procedure ◽  
Average Speed ◽  
The Road ◽  
Geometric Conditions ◽  
Sight Distance ◽  
Efficiency Measures ◽  
Vehicular Speed ◽  
On The Road ◽  
Design Speed

Mathematical models were developed to estimate vehicular speed on curves and tangents in mountain roads. The 85th percentile speed for curves was estimated by using the radius of the curve under consideration, the radius of the previous curve, sight distance in the curve, and tangent length before the curve. The average speed was calculated by using the radius of the curve under consideration, the radius of the previous curve, and sight distance. The 85th percentile and the average speed were estimated by using the radius of the previous curve and tangent length. Speeds adopted by drivers respond not to engineer’s design speed but to geometric characteristics of the road. A design procedure is proposed that takes advantage of available design speed and driver behavior on the road at the same time. On a curve, drivers consider two efficiency measures: speed and comfort. On some curves, they prefer to feel a certain degree of discomfort in exchange for obtaining greater speeds. For some geometric conditions, drivers adopt a speed that sacrifices not only comfort but also safety.

scholarly journals A Comparison between Effects of Linear and Non-Linear Mechanistic Behaviour of Materials on the Layered Flexible Pavement Response

2013 ◽  
Vol 723 ◽  
pp. 12-21 ◽  
Author(s):  
Behzad Ghadimi ◽  
Hamid Nikraz ◽  
Colin Leek ◽  
Ainalem Nega
Keyword(s):  
Granular Materials ◽  
Design Procedure ◽  
Numerical Approach ◽  
The United States ◽  
Pavement Design ◽  
Finite Element Program ◽  
Software Models ◽  
Non Linear ◽  
Current Design ◽  
Element Program

Modelling granular pavement materials has a significant role in the pavement design procedure. Modelling can be through an experimental or numerical approach to predict the granular behaviour during cyclic loading. The current design process in Australia is based on linear elastic analysis of layers. The analysis is performed through a well-known program CIRCLY which is applied to model bound pavement material behaviour. The KENLAYER is one of the common pavement software models used for pavement design in the United States which performs non-linear analysis for granular materials. Alternatively, a general Finite Element program such as ABAQUS can be used to model the complicated behaviour of multilayer granular materials. This study is to compare results of numerical modelling with these three programs on two sample pavement models.

scholarly journals Vehicle Suspension Design Based on a Six-Bar Linkage

2014 ◽  
Author(s):  
Mark M. Plecnik ◽  
J. Michael McCarthy
Keyword(s):  
Design Procedure ◽  
Vehicle Suspension ◽  
Total Degree ◽  
Vertical Alignment ◽  
The Road ◽  
Synthesis Technique ◽  
Vehicle Chassis

A synthesis technique for designing novel vehicle suspension linkages based on the Watt I six-bar is presented. The goal is to maintain near vertical alignment of the wheels to the road during cornering. The complete suspension is analyzed as a symmetric planar 12-bar linkage with ground pivots located at the contact patches. The design procedure specifies the vehicle chassis orientation and the tire camber angles of the vehicle when cornering. As well, two task positions of the wheels with respect to the chassis are specified for suspension movement in straightaways. The result is 18 design equations with 18 unknowns that have a total degree of 2,097,152, though only 336 roots. An example design is presented.

Highway Alignment: Three-Dimensional Problem and Three-Dimensional Solution

1998 ◽  
Vol 1612 (1) ◽  
pp. 17-25 ◽  
Author(s):  
Yasser Hassan ◽  
Said M. Easa ◽  
A. O. Abd El Halim
Keyword(s):  
Three Dimensional ◽  
Computer Software ◽  
Geometric Design ◽  
Analytical Models ◽  
Dimensional Solution ◽  
Distance Analysis ◽  
Sight Distance ◽  
The Status ◽  
Current Design ◽  
Highway Alignment

Highway geometric design has usually been considered in separate two-dimensional (2-D) projections of horizontal and vertical alignments. Such a practice was followed mainly because three-dimensional (3-D) analysis of combined highway alignments was expected to be difficult. As a result, the effect of ignoring the 3-D nature of the highway alignment could not be quantified. With the long-term objective of developing 3-D design practice, a framework for 3-D highway geometric design was developed and 3-D sight distance was extensively studied as the first design basis. The status of sight distance in current design policies and previous research is summarized, and mainly 2-D analysis was considered. The five main tasks performed to cover the 3-D highway sight distance are presented. ( a) As a preliminary step, the 2-D sight distance on complex separate horizontal and vertical alignments was modeled, and the finite element method was used for the first time in the highway geometric design. ( b) The 2-D models were then expanded to cover the daytime and nighttime sight distances on 3-D combined alignments. ( c) The analytical models were coded into computer software that can determine the available sight distance on actual highway segments. ( d) The models were applied in 3-D design of combined horizontal and vertical curves in cut-and-fill sections, and preliminary design aids were derived. ( e) Finally, a new concept of red zones was suggested to mark the locations on alignments designed according to current practices where the available sight distance will drop below that required. A comprehensive work on 3-D sight distance analysis has been compiled that should be of great importance for highway researchers and professionals.

Investigations of Road Wear Caused by Studded Tires

2014 ◽  
Vol 42 (1) ◽  
pp. 2-15
Author(s):  
Johannes Gültlinger ◽  
Frank Gauterin ◽  
Christian Brandau ◽  
Jan Schlittenhard ◽  
Burkhard Wies
Keyword(s):  
Traffic Safety ◽  
Test Bench ◽  
Operating Conditions ◽  
Test Method ◽  
Analytical Models ◽  
The Road ◽  
Driving Speed ◽  
Major Factors ◽  
Tire Friction ◽  
Variable Operating Conditions

ABSTRACT The use of studded tires has been a subject of controversy from the time they came into market. While studded tires contribute to traffic safety under severe winter conditions by increasing tire friction on icy roads, they also cause damage to the road surface when running on bare roads. Consequently, one of the main challenges in studded tire development is to reduce road wear while still ensuring a good grip on ice. Therefore, a research project was initiated to gain understanding about the mechanisms and influencing parameters involved in road wear by studded tires. A test method using the institute's internal drum test bench was developed. Furthermore, mechanisms causing road wear by studded tires were derived from basic analytical models. These mechanisms were used to identify the main parameters influencing road wear by studded tires. Using experimental results obtained with the test method developed, the expected influences were verified. Vehicle driving speed and stud mass were found to be major factors influencing road wear. This can be explained by the stud impact as a dominant mechanism. By means of the test method presented, quantified and comparable data for road wear caused by studded tires under controllable conditions can be obtained. The mechanisms allow predicting the influence of tire construction and variable operating conditions on road wear.

Sorting Out the Mixed Economy

2019 ◽  
Author(s):  
Amy C. Offner
Keyword(s):  
Latin America ◽  
Latin American ◽  
New Deal ◽  
The United States ◽  
Business Associations ◽  
Welfare Programs ◽  
The Road ◽  
Social Welfare Programs ◽  
The Third World ◽  
The New Deal

In the years after 1945, a flood of U.S. advisors swept into Latin America with dreams of building a new economic order and lifting the Third World out of poverty. These businessmen, economists, community workers, and architects went south with the gospel of the New Deal on their lips, but Latin American realities soon revealed unexpected possibilities within the New Deal itself. In Colombia, Latin Americans and U.S. advisors ended up decentralizing the state, privatizing public functions, and launching austere social welfare programs. By the 1960s, they had remade the country's housing projects, river valleys, and universities. They had also generated new lessons for the United States itself. When the Johnson administration launched the War on Poverty, U.S. social movements, business associations, and government agencies all promised to repatriate the lessons of development, and they did so by multiplying the uses of austerity and for-profit contracting within their own welfare state. A decade later, ascendant right-wing movements seeking to dismantle the midcentury state did not need to reach for entirely new ideas: they redeployed policies already at hand. This book brings readers to Colombia and back, showing the entanglement of American societies and the contradictory promises of midcentury statebuilding. The untold story of how the road from the New Deal to the Great Society ran through Latin America, the book also offers a surprising new account of the origins of neoliberalism.

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