  The operation of future intelligent transportation systems (ITSs),
communications infrastructure (CI), and power grids (PGs) will be highly
interdependent. In particular, autonomous connected vehicles require CI
resources to operate, and, thus, communication failures can result in
non-optimality in the ITS flow in terms of traffic jams and fuel consumption.
Similarly, CI components, e.g., base stations (BSs) can be impacted by failures
in the electric grid that is powering them. Thus, malicious attacks on the PG
can lead to failures in both the CI and the ITSs. To this end, in this paper,
the security of an ITS against indirect attacks carried out through the PG is
studied in an interdependent PG-CI-ITS scenario. To defend against such
attacks, the administrator of the interdependent critical infrastructure can
allocate backup power sources (BPSs) at every BS to compensate for the power
loss caused by the attacker. However, due to budget limitations, the
administrator must consider the importance of each BS in light of the PG risk
of failure, while allocating the BPSs. In this regard, a rigorous analytical
framework is proposed to model the interdependencies between the ITS, CI, and
PG. Next, a one-to-one relationship between the PG components and ITS streets
is derived in order to capture the effect of the PG components' failure on the
optimality of the traffic flow in the streets. Moreover, the problem of BPS
allocation is formulated using a Stackelberg game framework and the Stackelberg
equilibrium (SE) of the game is characterized. Simulation results show that the
derived SE outperforms any other BPS allocation strategy and can be scalable in
linear time with respect to the size of the interdependent infrastructure.
