  Intelligent Transportation Systems (ITSs) is the backbone of transportation
services in smart cities. ITSs produce better-informed decisions using
real-time data gathered from connected vehicles. In ITSs, Vehicular Ad hoc
Network (VANET) is a communication infrastructure responsible for exchanging
data between vehicles and Traffic Management Centers (TMC). VANET performance
(packet delay and drop rate) can affect the performance of ITS applications.
Furthermore, the distribution of communicating vehicles affects the VANET
performance. So, capturing this mutual impact between communication and
transportation is crucial to understanding the behavior of ITS applications.
Thus, this paper focuses on studying the mutual impact of VANET communication
and mobility in city-level ITSs. We first introduce a new scalable and
computationally fast framework for modeling large-scale ITSs including
communication and mobility. In the proposed framework, we develop and validate
a new mathematical model for the IEEE 802.11p MAC protocol which can capture
the behavior of medium access and queuing process. This MAC model is then
integrated within a microscopic traffic simulator to accurately simulate
vehicle mobility. This integrated framework can accurately capture the
mobility, communication, and the spatiotemporal impacts in large-scale ITSs.
Secondly, the proposed framework is used to study the impact of communication
on eco-routing navigation performance in a real large-scale network with real
calibrated vehicular traffic. The paper demonstrates that communication
performance can significantly degrade the performance of the dynamic
eco-routing navigation when the traffic density is high. It also shows that the
fuel consumption can be increased due to lack of communication reliability.
