  We describe traffic flows in one lane roadways using kinetic theory, with
special emphasis on the role of quenched randomness in the velocity
distributions. When passing is forbidden, growing clusters are formed behind
slow cars and the cluster velocity distribution is governed by an exact
Boltzmann equation which is linear and has an infinite memory. The
distributions of the cluster size and the cluster velocity exhibit scaling
behaviors, with exponents dominated solely by extremal characteristics of the
intrinsic velocity distribution. When passing is allowed, the system approaches
a steady state, whose nature is determined by a single dimensionless number,
the ratio of the passing time to the collision time, the two time scales in the
problem. The flow exhibits two regimes, a laminar flow regime, and a congested
regime where large slow clusters dominate the flow. A phase transition
separates these two regimes when only the next-to-leading car can pass.
