D.—l

Most districts experienced a particularly dry summer, and very little assistance was derived from rain in aiding compaction. However, funds which were not spent in sealing were diverted to further surface preparation. The Board prefers to see winter preparation undertaken so that compaction for several months under traffic in the wet season can be carried out; but financial considerations often prevent this. Surface-sealing has for the most part been adopted in the provision of dustless surfaces, as this method of treatment is all that can generally be economically justified under present traffic densities. As traffic increases the thickness of pavements can always be built up in stages. The surface treatment has been somewhat varied to suit local conditions and local preferences, and no hard and fast practice has been laid down. By far the greatest proportion of the work has been for a first coat of No. 1 tar followed by a coat of bitumen. In order of preference the work carried out would fall into the following class :— Ist Coat. 2nd Coat. No. 1 tar. Bitumen. No. 1 tar. Asphaltic road oil. No. 1 tar. No. 2 tar. Asphaltic road oil. Asphaltic road oil. Cold tar primer. Asphaltic road oil. Cold tar primer. Cold emulsion. Cold emulsion. Cold emulsion. The Board encourages the use of tar, as a local product, where tar can be economically justified. Unfortunately most of our gas-works are of the vertical-retort type, so that the tar produced is mainly suitable for priming and first-coat work only. The road-mix and plant-mix surfacing was carried out principally in the Canterbury and Wellington Districts. This type of work is particularly suitable where the local gravels are abundant and the subgrades consist of gravel and river silt. A dry climate also suits this type of construction, and the cost is very little more than the ordinary two-coat sealing work. In fact, when alternative tenders were called, some tenders for plant-mix were lower than some submitted for sealing. Construction. The expenditure from the Construction Fund for the year 1934-35 was £325,483, an increase of about 54 per cent, on the expenditure for the preceding year. The table below shows the extent and types of work carried out on main-highways system by the Board and local authorities since the Board commenced active operations in 1924.

Bridges. In past years when it was necessary to give settlers access in the shortest time for the least possible initial outlay, many of the bridges now included in the highways system were built of local softwoods. These are all due for replacement. It is also found that quite a few of the bridges built of imported hardwoods are suffering from premature decay. These hardwood bridges are those which were built during the war period, when the quality of the timber supplied was not nearly as good as normally. Realizing the importance of maintaining vital traffic links, the Board undertook a vigorous programme of bridge replacement. Including those already in hand at the beginning of the year, funds were provided for 260 bridges. Of these, 128 were completed during the year. A further 123 are at various stages of progress towards completion, and many have been completed since the 31st March, 1935, the notable ones being the Balclutha Bridge, which was opened by the Minister of Public Works on the 6th April, 1935, the 8*

115

Formation Gravelling Tar and Bituminous PortlandYear. and and Bituminous Macadam Bituminous Widening. Metalling. Sealing. ' Z) Miles. Miles. Miles. Miles. Miles. Miles. Miles. Ft. 1924-25.. .. 19 63 6 .. 6 2 434 1925-26.. ..45 88 16 45 4 6 5*168 1926-27.. .. 174 151 35 .. 38 12 16 6 408 1927-28.. .. 173 133 83 .. 34 .. 6 7 760 1928-29.. .. 224 185 122 .. 51 14 11 9'482 1929-30.. .. 173 179 133 .. 39 31 12 7 547 1930-31.. .. 130 128 95 41 14 9 11,175 1931-32.. .. 139 69 129 32 9 3 4 062 1932-33.. .. 56 45 72 .. 8 .. .. 3 178 1933-34.. .. 44 28 75 .. 7 .. 1 4*988 1934-35.. .. 113 69 172 27 3 2 6,641 Totals .. 1,290 1,138 938 27 304 84 66 68,843