  We study completely asymmetric 2-channel exclusion processes in 1 dimension.
It describes a two-way traffic flow with cars moving in opposite directions.
The interchannel interaction makes cars slow down in the vicinity of
approaching cars in other lane. Particularly, we consider in detail the system
with a finite density of cars on one lane and a single car on the other one.
  When the interchannel interaction reaches a critical value, traffic jam
occurs, which turns out to be of first order phase transition. We derive exact
expressions for the average velocities, the current, the density profile and
the $k$- point density correlation functions. We also obtain the exact
probability of two cars in one lane being distance $R$ apart, provided there is
a finite density of cars on the other lane, and show the two cars form a weakly
bound state in the jammed phase.
