  This Letter studies a weakly and asymmetrically coupled three-lane driven
diffusive system. A non-monotonically changing density profile in the middle
lane has been observed. When the extreme value of the density profile reaches
$\rho=0.5$, a bulk induced phase transition occurs which exhibits a shock and a
continuously and smoothly decreasing density profile which crosses $\rho=0.5$
upstream or downstream of the shock. The existence of double shocks has also
been observed. A mean-field approach has been used to interpret the numerical
results obtained by Monte Carlo simulations. The current minimization principle
has excluded the occurrence of two or more bulk induced shocks in the general
case of nonzero lane changing rates.

Statistical Mechanics;Adaptation and Self-Organizing Systems