critical density of rods for the isotropic case.

Transport properties and in particular the electrical conductivity of systems filled with anisotropic conducting particles are closely related to geometric percolation behavior. The electrical percolation can reflect not only the geometric connectivity of the particles but also aspects of the charge transfer mechanism between individual particles [@Berhan2007]. The conductivity exponent $t$ for the 2D percolation of rods has been discussed in several works [@Balberg1982; @Balberg1983; @Hecht2006; @Li2010; @Zezelj2012]. Experimental studies on the electrical conductivity in a composite of conducting rods gave the following interval for the conductivity exponent, $1.5<t<2.1$ [@Balberg1982]. Balberg et al. obtained a value of $t=1.24\pm0.03$ by analyzing the conductivity of a percolation cluster of rods [@Balberg1983]. On the contrary, for the situation with differences between the resistances inside the rod, $R_s$, and at the rod-rod junctions, $R_j$, it was proposed that the conductivity exponent $t$ can vary from $0$ when $R_j\ll R_s$ to the universal value of lattice percolation, $t\simeq 1.3$ when $R_j\gg R_s$ [@Hecht2006]. Subsequently, MC simulations indicated that the $t$ value extracted from the size-dependent conductivities of systems exactly at the percolation threshold was independent of $R_j/R_s$ ($t=1.280\pm 0.014$) [@Li2010]. However, the $t$ value extracted from the 