GB2219331A - White surface-dressed roads - Google Patents

Abstract

A method of re-surfacing a road comprises applying a spray binder and reflective stone chippings and subsequently pressing down said chippings. The chippings are suitably white calcined flint of 5-20mm gauge.

Description

WHITE SURFACE DRESSED ROADS This invention relates to the re-surfacing of roads, carriageways, streets, airport runways and any other paved areas carrying vehicular traffic, with a white finish in combination with black contrasting markings.

All such surfaces shall hereafter for convenience be referred to as "roads".

It is desirable that the surface of roads should be as white in colour as possible. This is to make them safer at night to all road users. The driver of a vehicle at night with headlights on would see an expanse of whiteness ahead of him instead of the conventional area of blackness, enabling him to assess more easily the presence of other vehicles or other road users. Conventional white markings on such surfacing would be almost indiscerable, and it is therefore considered that all markings, e.g. lane divisions, stop and give ray lines, directional arrows, etc., should be in black.If proof be required that at night black on white contrasts far better than white on black, then one only hes to compare the readability at night of the front registration plate of an oncoming vehicle - black letters and figures on a white backplate - with those of yesteryear - white (or silver) letters and figures on a black backplate. Incidentally, legislation making this change mandatory seemed to happen overnight at some time late in 1969 or early 1970. Legislation, no doubt, would also be required for what is proposed by the present invention. It is considered that this invention would be particularly desirable on rural roads having no footway(s), no overhead lighting, and where pedestrians and cyclists are fairly common during the hours of darkness.

With further reference to road markings, these could be put down on the newly finished surfacings using a hot applied black thermoplastic material, preceded by a bituminous tack coat. For paved areas carrying @@inly light and/or slow moving traffic - car parks, for example - a black chlorinated rubber paint could be used. Road edge markings, if considered necessary, would also be in black, Solid glass reflective beads, almost invariably incorporated into conventional white markings, would not be required in the proposed black markings, allowing considerable saving in cost.

According to the present invention, surface dressing has four main purposes, viz: i To seal the road surface against penetration by ii To arrest disintegration iii To provide a non-skid erin surface iv And that the latter is totally rhite in appearance.

It becomes necessary to surface dress when the existing surface appears to have deteriorated, becoming finely crazed and allowing water to seep in, or if the skid resistance falls below 0.55 (sideways force coefficient) at a test speed of 50 km/h.If the road needs to be patched, when this work should be done considerably in advance of the surface dressing, and preferably during the previous season. The actual surface dressing should only be carried out between the months of April end September - May and August in some northerly areas and then only when the weather is god.

A specific embodiment of the invention rill now be described by way of example in which the laying of a hite surface dressing on an existing tarmacadam road is described.

Firstly the existing surface should be regulated. This involves sweeping the surface with a mechanical sweeper in order to remove all dust, grit and other loose material.

The road should then be checked for line and level. Any hollows and/or depressione in the existing wearing course should be cut back at the edges, just sufficiently to provide a key for new material, which should consist of the laying of a t@ck coat and filling with 10mm tarmacadam, or similar. Any pot holes should be cut back and dug out until sound material is reached, and re-filled and rammed in layers to match the existing road. The repaired areas should then be rolled with E 6 - 8 tonne roller.The road surface should then be left for @ period of ti1e before dressing to allow for natural sealing by dust, traffic, etc., or alternatively, blind immediately with a suitable dry sealer such as cement/sand grit, or 3mm coated bituminous seal in grit. The latter may b laid over the nev material covering e slightly larger arer of the same, and then be feathered out to virtually zero thickness, end so avoiding any tendency to fret.All ironwork - manhole covers and frames, @ullg dreinage grids, cats eyes, shoul be masked, and if the letter process is used then this should be Cone prior to its application. A spray binder should now be applied, which may be of refined road tar, cut-back bitumen, tar-bitumen blends or bitumen emulsion.

A mechanical distributor should preferably be used, fitted with rressure and speed indicators to ensure an accurate rate of spread end even thickness of binder from the swirling spray type nozzles. The vehicle then travels at a predetermined speed to give the required rate of spread.

Following the completion of this process, all maskings covering the ironwork, etc. , are removed, and the actual surface dressing is applied. This should consist of the uniform distribution of white calcined flint chippings varying between 5mm and 20mm gauge by a mechanical spreader, preferably fitted with a metering device in order to ensure an even carpet or coating over the sprayed road surface. In order to make sure that the film of binder is fully covered it is necessary to apply the chippings in excess of the actual quantity required.

Rubber-tyred rollers should immediately follow the the spreading o of the chippings in order to press in the latter. Excess loose chippings should be swept up and collected before traffic being allowed on to the completed surface - possibly between 15 and 30 minutes thereafter - depending on the weather conditions at the time.

to Should it be found desirable surface dress a road having a particularly hard surface - concrete, for example, then it is recommended that a smaller size of chippings be used - varying from say 5mm to 10mm gauge.

Although in the afore-described invention white calcined flint chippings have been examplified because of their consistent whiteness, high Polished Stone value and reflective qualities, it would not be unacceptable to use other chippings available, provided they possess similar or better qualities, as latterly stated. than white calcined flint.

It might be said that white surface dressed roads of the type proposed bg the present invention would tend to become gradually blemished by traffic film. This is not to be denied, but it is contended that such surfacings would continue to remain light in appearance during their normal lifetime - about five years - when they would become due to be similarly re-dressed on account of traffic wear and consequent loss of skid resistance.

Claims (7)

1 A method of re-surfacing an existing road with a white reflective material, the method consisting of the application to the road of a spray binder, applying thereto reflective stone chippings, and pressing down the said chippings.

2 A method according to claim 1 wherein the size of the stone chippings is between 5mm and 20mm gauge.

3 A method according to claim 1 wherein the size of the stone chippings is between 3mm and 10mm gauge.

4 A method according to any of the preceding claims wherein the chippings are dressed in by rolling.

5 A method according to any of the preceding claims wherein the chippings are white calcined flint.

6 A method according to claim 1 and substantially as herein described.

7 A method of re-surfacing an existing road with a white reflective material, substantially as described in the specific example.