  Vehicular ad-hoc networks have been defined in the literature as
communications networks that allow disseminating information among vehicles to
help to reduce traffic accidents and congestions. The practical deployment of
such networks has been delayed mainly due to economic and technical issues.
This paper describes a new software application to detect traffic incidents and
exchange information about them, using only smartphones, without any central
authority or additional equipment. Both road safety and communication security
have been taken into account in the application design. On the one hand, the
interface has been designed to avoid distractions while driving because it
operates automatically and independently of the driver, through voice prompts.
On the other hand, communication security, which is essential in critical
wireless networks, is provided through the protection of attributes such as
authenticity, privacy, integrity and non-repudiation. All this is achieved
without increasing the price of vehicles and without requiring the integration
of new devices neither in vehicles nor on roads. The only prerequisite is to
have a smartphone equipped with Wi-Fi connectivity and GPS location in each
vehicle. The proposed application has been successfully validated both in
large-scale NS-2 simulations and in small-scale real tests to detect traffic
congestions and empty parking spaces.
