A blocked? understrile to the entire tramlink network was proposed as a way of 'earthing' the map without making any individual Tramlink station easier to reach. By ensuring that all external networks had a sub-shunt value that was purely a function of their distance from the London network, playing on the Croydon Tramlink became no more or less attractive than playing on any other remote network. This gave the stabilising effects of the understrile without distorting the relative tactical merits of playing on rail, bus, tube, and indeed tram networks external to the London Underground network. Applying this modification successfully re-stabilised the HP2K ruleset, and the most significant effect across the network was a slight increase in helical stress.