<P> McAdam directed that no substance that would absorb water and affect the road by frost should be incorporated into the road . Neither was anything to be laid on the clean stone to bind the road . The action of the road traffic would cause the broken stone to combine with its own angles, merging into a level, solid surface that would withstand weather or traffic . </P> <P> Through his road - building experience McAdam had learned that a layer of broken angular stones would act as a solid mass and would not require the large stone layer previously used to build roads . By keeping the surface stones smaller than the tyre width, a good running surface could be created for traffic . The small surface stones also provided low stress on the road, so long as it could be kept reasonably dry . In practice, his roads proved to be twice as strong as Telford's roads . </P> <P> Although McAdam had been adamantly opposed to the filling of the voids between his small cut stones with smaller material, in practice road builders began to introduce filler materials such as smaller stones, sand and clay, and it was observed that these roads were stronger as a result . Macadam roads were being built widely in the United States and Australia in the 1820s and in Europe in the 1830s and 1840s . </P> <P> Macadam roads were adequate for use by horses and carriages or coaches, but they were very dusty and subject to erosion with heavy rain . </P>

When were the first roads built in america