TRANSPORTATION ENGINEERING II

Pavement design standards

IMPORTANCE

• In our daily life, we follow some standards which are universally acceptable. This leads to simplification of various unforeseen problems that might be faced in relevance.

• We are usually unaware of the role played by standards in raising Levels of quality, Safety, Reliability and Efficiency- As well as in providing such benefits at an economical cost.

• Standards make an enormous contribution to most aspects of our lives - although very often, that contribution is invisible. For example, as purchasers or users of products, we soon notice when they turn out to be of poor quality, do not fit, are incompatible with equipment we already have, are unreliable or dangerous.

STANDARDS FOLLOWED

• Different standards are being followed in the world by different countries, suiting their environmental conditions and other resources.

• Following are the different standards.– British Standards

• Transport and Road Research Laboratory (TRRL) Road Note 31.

– USA Standards• AASHTO (American Association of State

Highway & Transportation Officials).

BRITISH STANDARD

• Factors involved in formulating design suitable for a particular situation are – Present Commercial Traffic– Growth rate of commercial traffic– Design life required– ESAL’s– Thicknesses of different pavement

layers

USA STANDARDS

• AASHTO Guide for design is the standard followed in USA.

• The major difference in the USA and British standard is the concept of failure criterion. In British standards, the failure conditions are deformation and cracking where as in USA, failure is defined in terms of quality of ride, known as Present Serviceability Index (PSI).