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15. Horizontal Alignment II

The chapter covers essential principles of horizontal alignment, focusing on the design and implementation of superelevation in roadway engineering. It highlights guidelines and formulas for ensuring road safety for various types of vehicles while navigating curves, along with concepts of mechanical and psychological roadway widening. The discussion emphasizes the importance of considering both design speed and lateral friction in determining appropriate superelevation and curve radius.

Sections

Horizontal Alignment II

This section covers the design of superelevation in road geometry and the necessary guidelines for ensuring safety on curves.

15 Section Overview

Start current section content and materials

15.1 Overview

This section provides an overview of superelevation design and associated pavement widening considerations for road curves.

15.2 Guidelines on superelevation

This section outlines the design guidelines for superelevation in road construction, considering various vehicle types and traffic conditions.

15.2.1 Design of super-elevation

This section outlines the principles of designing super-elevation for safe road curves, considering vehicle dynamics and traffic conditions.

15.2.2 Maximum and minimum super-elevation

This section discusses the IRC guidelines for maximum and minimum super-elevation related to slow-moving vehicles and heavy-loaded trucks.

15.2.3 Attainment of super-elevation

This section explains the methods used to attain super-elevation on roadways, including the elimination of pavement crown and various methods of cross-section rotation.

15.3 Radius of Horizontal Curve

The radius of horizontal curves is critical for determining safe driving speeds and is influenced by factors such as superelevation and friction.

15.4 Extra Widening

Extra widening is the additional carriageway width required on curved road sections due to mechanical and psychological effects.

15.4.1 Mechanical widening

Mechanical widening is the additional carriageway width required on a curved road to accommodate vehicle dynamics, particularly the off-tracking phenomenon.

15.4.2 Psychological widening

Psychological widening addresses the need for additional pavement space at curves to accommodate drivers' tendencies to drive closer to the road edges.

15.5 Summary

This section summarizes the design principles of superelevation as mandated by IRC guidelines for road safety, particularly at curves.

15.6 Problems

This section presents various problems related to the design of superelevation and pavement widening at curves for a national highway.

Learning Objectives

  • Superelevation is crucial for road safety, particularly in curves, requiring careful design based on vehicle types and speeds.

  • IRC guidelines establish maximum and minimum values for superelevation depending on terrain and vehicle dynamics.

  • Extra widening is necessary at curves to accommodate both mechanical and psychological factors affecting vehicle movement.

Key Concepts

Superelevation

The banking of a roadway at a curve, designed to counteract the effects of centrifugal force, enhancing vehicle stability.

Mechanical Widening

The increase in roadway width required due to the off-tracking of vehicles negotiating a curve.

Psychological Widening

The additional width provided on curves to give drivers a sense of extra space and security.

Radius of Horizontal Curve

The distance from the center of a circular curve to its outer edge, which affects speed and safety on curves.

Practice Exercises

Total Questions

2

Estimated Time

4 min

Passing Score

70%

Instructions

  • Read each question carefully
  • You can use hints if you need help
  • Complete all questions before submitting

1 more question available

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