3. METCALF ROADS

   1. JOHN METCALF was engaged in road construction in England.

   2. He is responsible for construction of a 290 km  road in north england.

   3. Road was similar to tresaguet roads.

4. TELFORD ROADS

   1. Stones of varying size (17-22)cm were used for road construction.

   2. Among this layer , angular broken stones of 7 cm size and 10cm thickness were used.

5. MACADAM ROADS

   1. Subgrade is compacted and prepared with a cross slope of 1 IN 36 up to a desired width (about 9 m).

   2. Broken stones of a strong variety, all passing through 5 cm size sieve were compacted to a uniform thickness of 10 cm.

   3. The second layer of strong broken stones of size 3.75 cm was compacted to thickness of 10 cm

   4. The top layer consisted of stones of sizes less than 2 cm compacted to a thickness of about 5 cm and finished so that the cross-slope of pavement surface was also 1 in 36. 

NOTE: Different types of specification  were developed for constant bituminous pavement layers for use in the base of surface course.

Some of the specification used in India are as follow:-

1. Water bound macadam

2. Penetration macadam

3. Bituminous macadam

4. Dense bound macadam

5. Wet mix macadam