  Urban Traffic Management (UTM) topics have been tackled since long time,
mainly by civil engineers and by city planners. The introduction of new
communication technologies - such as cellular systems, satellite positioning
systems and inter-vehicle communications - has significantly changed the way
researchers deal with UTM issues. In this survey, we provide a review and a
classification of how UTM has been addressed in the literature. We start from
the recent achievements of "classical" approaches to urban traffic estimation
and optimization, including methods based on the analysis of data collected by
fixed sensors (e.g., cameras and radars), as well as methods based on
information provided by mobile phones, such as Floating Car Data (FCD).
Afterwards, we discuss urban traffic optimization, presenting the most recent
works on traffic signal control and vehicle routing control. Then, after
recalling the main concepts of Vehicular Ad-Hoc Networks (VANETs), we classify
the different VANET-based approaches to UTM, according to three categories
("pure" VANETs, hybrid vehicular-sensor networks and hybrid vehicular-cellular
networks), while illustrating the major research issues for each of them. The
main objective of this survey is to provide a comprehensive view on UTM to
researchers with focus on VANETs, in order to pave the way for the design and
development of novel techniques for mitigating urban traffic problems, based on
inter-vehicle communications.
