Bituminous Surface Treatments (BST) have been used on Yukon highways since the late 1970s in order to provide an improved level of service to the traveling public.
BST was initially used for dust control on gravel roads as an alternative to calcium chloride and has since been developed as an inexpensive paved surface on low volume roads.
There are approximately 1,860 kilometres of BST on the Yukon territorial highway system.
The system divide the BST roads into three distinct classes:
Class 1 includes all roads on which the BST has been applied to an unimproved road structure which has not been designed to any particular standard.
Class 2 includes roads on which a 75 to 150 mm thick layer of crushed gravel base course is placed on the sub grade prior to BST application.
Class 3 is comprised of roads with fully designed sub-base and base course layers on which BST has been applied as a substitute for hot-mix asphaltic concrete.
The cost of applying BST varies depending on the geographical area being worked and the proximity of that area to emulsion supply and gravel resources. Generally speaking in the southern area of the Yukon (Whitehorse - South) BST treatment costs slightly more than in northern Yukon
One of the more significant costs in the management of BST is the ripping up of the old surface and preparation for the application of the new BST surface. It's important not to waste the old BST surface (asphalt and aggregate).
The asphalt residue provides strength in the base and the aggregate costs money to produce and apply. Our focus has been to find cost effective methods to tear up the old BST surface and break it down to a workable size so that it can be reintegrated into the surface.
Transportation Maintenance Branch applies approximately 200 km of BST per year. This normally is broken down to 25 - 30 km of BST on newly reconstructed road and the remainder is replacing an already existing BST surface.