MODERN ROADS

Wanganui Chronicle, Volume 73, Issue 95, 23 April 1930, Page 11

MODERN ROADS

IMPROVING CORNERS BANKING AND WIDENING Since the Main Highways Board took charge of arterial roads great improvements of a necessary nature have been laid down with some form of highclass pavement, heavy grades have been eased and dangerous alignments have been improved. Now that the spade work is practically completed, we can expect some of the refinements of modern road practice. A circular recently issued to engineers in charge of sections of highway draws their attention to the necessity of superelvation of curves. Every motorist knows the satisfaction of driving on a road where the corners are carefully banked and no effort is required to negoti ate them, the reason being that the tendency of the car to pull off the road is resisted by the slope towards the inside of the curve.

Careful study has led to the adoption of a formula by which the correct slope for a curve of any radius can be calculated once the safe maximum speed has been decided. This formula has been put in graph form and the following cambers recommended for its consideration:— Curves up to 2 chain radius, IJin. per foot of width; curves from 3 chains to 7 chains radius, lin. per foot of width; curves from 8 chains to 15 chains radius, fin. per root of width; curves from 16 chains to 40 chains radius, IJin per foot of width. All who use the roads to any extent must be well aware of numerous cases that do not measure up to these standards. A further refinement will be the provision of additional width on curves, necessary because in cornering the rear wheels do not follow exactly in the track of the front wheels, but cut inside them, so tnat a car takes up a greater width or road on a curve than it does on the straight. The additional width recommended varies from 5 feet for curves to 3 chains radius of 2 feet for curves of 10 chains radius. With curves of greater radius the necessity for this additional width disappears. In a country largely dependent on primary products our roads are widely used, so that a large proportion of the community will benefit from the improvements contemplated.