BITUMINOUS ROADS.

Hawera Star, Volume XLVI, 28 May 1927, Page 15

BITUMINOUS ROADS.

L RECORDS OF EARLY PAVING.

QUALITIES OF ASPHALT

Looking back over the perspective of the paving art from the earliest historical records, we find .among the first references that asphalt had been used as a filler or mortar ior_ brick pavements and cementing the walls in the streets of Babylon and other Biblical cities about five thousand years before the Christian ena.

Prescott, the noted historian, gives a very interesting account ot the use of bituminous cement by the ancient Peruvians for the construction of highways in the Andes mountains, the bituminous cement being used as a binder for flag-stones; he recites that these highways are still in evidence, in some cases bridging over chasms formed by' the erosion of storm water. In the 18th century deposits of natural bitumen were discovered in parts qi France and Germany. This product, in 1802, began to find a ready market for bodge and sidewalk surfaces, and in 1838 asphalt sidewalks were constructed in Philadelphia. Between 1850 and 1860 a number of streets in Paris were paved with asphalt, and in 1869 Threadneedle Street in Loudon was paved with rock asphalt. Further impetus was given to asphalt pavings in 1879 through the discovery that high-grade asphalt could be obtained by the distillation of asphaltic base crude oils. ' The efficiency o.f the earlier forms of asphaltic construction; is not to be compared with the efficiency of the highly developed construction of to-day. The old construction was nothing more than a layer of. crushed stone, more or less impregnated with some adulterated form of asphalt. in the earlier centuries labour had but little value, and highways were constructed in massive proportions. During the 19t.h century, in the face of advancing labour costs, effort was directed towards producing a pavement just as efficient as the ancient highways but much thinner, and at. a much less comparative expense. It was hoped to no-. conupli'Slh this result by the use of more efficient materials and highly specialised labour.

The predominating character of pavements prior to the 20th century, was a flexible asphaltic wearing surface supported by a rigid or semi-regid base; but now, generally speaking, paving engineers are directing their energies to the development of a. pavement in which the whole structure, base and wearing surface, .should be of one standard, thereby eliminating certain objections of a mechanical and economical nature. There are, however, on the one side advocates of the rigid type of base, strongly advising that the base course should be extended and enlarged so as to include the wearing surface ; on the other side we have the advocates of a flexible base advancing the theory that the same elements, suitable in -a. wearing surface might profitably be extended and increased in thickness so as to include the base. The arguments presented in support of both types have been very prolific, and have ted. both in Europe and America, to very considerable controversy. These two schools of argument differ very esentia'lly in fundamental principles-. One of them seeks to counteract and resist the destructive effects of traffic impact, sometimes as much as six or seven times the normal static loading, by means of a rigid slab, designed of greater strength than the force of such impact; the other school seeking to absorb and dissipate the same traffic impact in a flexible structure always in actual contact with the subgrade, thereby ensuring a greater uniformity of load distribution. The flexible type ,i$ peculiarly adapted to absorbing impact and distributing the load upon the subgrade, because by its nature it will always remain in intimate contact with the sub-grade, regardless of temperature or moisture conditions. It is a peculiarity of asphalt construction that it should be subjected to traffc- immediately and continuously in order to produce, an efficient pavement; asphalt construction is benefited by the kneading action of constant traffic.

Another peculiar instance of the sliock absorbing qualities of asphaltic concrete occurred in the city of Spokane in February of this year. Owing to ia> short circuit, many explosions in gas mains occurred in the business ■section of the city, causing considerable breakage of window glass, but no injury of any nature to the asphaltic pavement.—Contributed by the British Imperial Oil Company (N.Z.) Ltd.

SCIENTIFIC DRIVERS’ TEST.

The laboratories of the Leipzig University, Germany, contain some remarkable instruments for scientifically testing the mental reactions of motor drivers. Tests have been evolved which make it possible to detect the man who is a potential danger on the road. Chauffeurs who. seek licences to drive in busy traffic cannot disguise any nervousness or incapacity from these instruments. For the purpose of one test the. driver sits at an ordinary set of ear controls while a moving screen ahead brings various traffic situations before him. His actions when cronfronted with these contingencies are registered by .a delicate graph instrument, and any .indecision is revealed. Another device measures degrees of fatigue. The subject grips two handles for a definite period and any relaxat ions of the muscles are measured. A very complicated .instrument records reactions to noises and alarms, and another mechanism indicates the coordination, between the hand and the brain.

RIGHT HAND CONTROL LEVERS

After at one time .appearing to have nearly gone out of fashion, there has of late been a distinct revival of the .right-hand position for the changespeed brake levers. Coincident with this course in design is q practically universal demand lor four doors, or at any rate a door to the driver’s seat. Many makers standardise the latter, highly desirable feature, but by placing, as it were, a. hurdle in the doorway in the shape o; a couple of levers, largely nullify their good intentions.

Probably a majority of motorists, if a referendum were taken, would eh: ose light-hand contro.s, but almost certainly, also, they would specify a c’oor tr the driver’s .seat, and if it were shown to them that the two do not always go well together, particularly on the shorter and smaller chassis, would willingly sacrifice their desire for righthand controls if by doing so they could recu.ro laibsolute ease of ingress and egress in their cans.