Road Ice Skid Resistance Treatments on Upper Natone Road, Tasmania

Walsh, Alec (2017) Road Ice Skid Resistance Treatments on Upper Natone Road, Tasmania. [USQ Project]


Road ice, also termed ‘black ice’, is a serious hazard and consists of a thin layer of transparent ice on the surface of the road. If not adequately monitored and addressed, it can result in serious or fatal motor vehicle accidents. The microclimate of a site and friction provided by the road surface is integral in the formation of road ice and the subsequent available skid resistance. Treatments, such as the application of de-icing chemical are often applied to melt snow and ice and other maintenance practices such as gritting, through the spreading of crushed aggregate on the road surface, may also improve skid resistance in frost, ice and snow.

This report analyses two sites on the North-West Coast of Tasmania that are subjected to road ice in winter. Site 1 is an asphalt sealed rural road located south of the township of Natone. This section of road lays on a steep gradient (>14%) and is heavily shaded by vegetation. The site receives a maintenance treatment of gritting with crushed aggregate. Gritting is intended to improve the texture of the road surface, when road ice has formed; however, the community has raised concerns with this treatment and a review, together with possible alternatives is considered.

Site 2 is a steep section of sprayed seal rural road, subjected regular Heavy Vehicles (HV), from forestry and mining operations. Heavy axle repetitions have caused the seal aggregate to become polished and bitumen to bleed to the surface. Ultra-high-pressure water cutting (UHPWC) has been used to remove some of the bleed bitumen and return a degree of texture to the road surface. The site is due to be resealed and the formation of road ice is highlighted as a key design consideration.

This report compares various seal treatments, using a Pendulum ‘Skid Resistance’ Tester to measure skid resistance and the ‘Sand Patch Test’, to determine macrotexture when subjected to ice. Seal samples were sourced from a local supplier, with different aggregates sizes and varying polished aggregate friction values (PAFV). This report reviews the test methods and standards and considers investigatory level of skid resistance and surface textures, for comparison with the empirical results. The report also considers geometry and the effectiveness of various maintenance treatments that are applied to roads affected by ice.

Results concluded asphalt, due to low macrotexture, performed poorly when subjected to ice. Sprayed seals with coarse macrotexture, using large aggregates, such as 10 and 14mm, in combination with high PAFV and together with the maintenance methods reviewed, can increase skid resistance when a road surface is frozen. From these results, a double/double preliminary sprayed seal design is recommended for Site 1 & Site 2, and as necessary, correctly applied maintenance through gritting or ultra-high-pressure water cutting can greatly improve skid resistance and limit the impact of winter road ice.

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Item Type: USQ Project
Item Status: Live Archive
Additional Information: Bachelor of Engineering (Civil)
Faculty/School / Institute/Centre: Historic - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying (1 Jul 2013 - 31 Dec 2021)
Supervisors: Nataatmadja, Andreas
Date Deposited: 08 Sep 2022 02:06
Last Modified: 08 Sep 2022 02:06
Uncontrolled Keywords: black ice; skid resistance; treatment; de-icing chemical

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