This Road Note is the 2nd edition of Overseas Road Note 3 'A guide to surface dressing in tropical and
sub-tropical countries'.

The revisions include descriptions of a wider range of types of surface dressing, current materials specifications and more detail on the use of bitumen emulsions. An equation has been introduced to allow the design spray rate to be calculated as an alternative to reading from a nomograph. A simplified presentation of spray rate adjustment factors, related
to different site conditions, has also been provided.

The durability of surface dressings, particularly for low volume roads, is discussed and additional spray rate adjustment factors have been suggested for these roads. The use of Otta seals has also been suggested for low volume roads.

It is important that this Road Note, is not regarded as a specification. However, the advice contained in this
Road Note together with local experience of relevant materials and surface dressing performance should be
of value to those drawing up specifications.

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