Abstract

Mr P. D. Thompson of the Road Research Laboratory, Ministry of the Environment introduced the Third Edition of Road Note 29 (Road Research Laboratory 1970) and discussed the main design recommendations.

Road Note No. 29 was first published in 1960 to provide a guide to the structural design of roads carrying medium and heavy traffic. The 1965 revision widened the scope to include lightly trafficked roads, such as those used in housing estates. Otherwise only relatively minor changes were made to the earlier edition.

Since 1960 the annual expenditure on the construction of new roads has increased fourfold. This alone provides sufficient reason for a detailed re-examination of all the recommendations given in the last edition. The growth rate of commerical traffic on many of the roads recently built has proved to be more than the 4 per cent annum allowed for 10 years ago; this means that there are on some roads daily flows of commerical traffic already exceeding the 6000-8000 vehicles that the original drafting committee had in mind as a maximum after 20 years. The size of the commerical vehicles in use has also tended to increase, and this has resulted in a greater proportion of heavier axle loads.

The present revision was drawn up within the Ministry of Transport in close consultation with a Panel set up by the Laboratory's Research Committee on Design and Construction. The Panel included county surveyors and consulting engineers.

This note deals solely with the construction of new roads and not

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