  With the emergence of autonomous driving and 5G mobile communication systems,
how to design vehicular networks to meet the requirements of ultra-reliable
low-latency communication (URLLC) between autonomous vehicles is widely
concerned by the academia and industry. In this paper, message transmission
delay and reliability between autonomous vehicles based on millimeter wave
(mmwave) multi-hop V2V communications under urban road environment are
investigated. Considering the fact that vehicles cannot come arbitrarily close
to each other, shifted-exponential distribution is proposed to model the
headway distance (the distance between the head of a vehicle and the head of
its follower). Simulation results show that message transmission delay and
reliability decrease with the increase of the path loss exponent and are also
affected by the minimum safe distance between adjacent vehicles.
