## 2 Related Works  
Many congestion avoidance systems using VANET have been proposed recently; [PERSON] et al. [13] proposed a real-time path-planning algorithm, where a stochastic Lyapunov optimization technique is exploited to improve the overall spatial utilization of a road network and reduce the average vehicle travel cost for avoiding vehicles from getting stuck in congestion. A vehicle rerouting system called Next Road Rerouting (NRR) is proposed in [14], where a heuristic rerouting decision is made upon a cost function that takes into account the driver's destination and local traffic conditions. [PERSON] et al. [15],proposed SAINT, a cloud-based vehicular traffic optimization system, in which the vehicles report their navigation experiences and travel paths to the vehicular cloud, thus, the vehicular cloud can know real-time road traffic conditions and vehicle trajectories; the vehicular cloud uses a mathematical model to calculate road segment congestion estimation for global traffic optimization. [PERSON] et al. [PERSON] et al. (2016) proposed DIVERT, a distributed vehicular re-routing system for congestion avoidance. DIVERT offloads a large part of the re-routing computation to the vehicles, and thus, the re-routing process becomes practical in real-time. To take collaborative re-routing decisions, the vehicles exchange messages over VANET. However, DIVERT is not an infrastructure-less system because it still uses a server and internet connectivity to determine an accurate global view of the traffic. The work in [PERSON] et al. (2017) presented RoadRunner, a congestion control system implemented as an Android app that relies on LTE network and V2V communications. The proposed system distributes tokens to vehicles as permission for their entry into roads; tokens are provided and managed by a centralized server. However, the systems presented in [PERSON] et al. (2016); [PERSON] et al. (2016); [PERSON] et al. (2016); [PERSON] et al. (2016), assume the existence of pre-installed infrastructures, such as RSU or cellular network. As far as we know, DIFTOS is the first system that is completely infrastructure-free and does not rely on any existing infrastructure such as RSU or cellular network. In Table 1 a comparison between DIFTOS and state-of-the-art systems is presented. Besides the traffic congestion avoidance systems, many works have used VANETs for traffic related applications. [PERSON] et al. [PERSON] et al. (2018) developed a new protocol, named as the Traffic Accidents Reduction Strategy (TARS), for VANET to minimize the number of road accidents, and decrease the death rate caused by road accidents. The simulation results showed that their proposed scheme has outperformed DBSR and POVRP routing protocols. [PERSON] et al. [PERSON] et al. (2018) presented a novel scheme to select important safety messages for verification. The proposed scheme uses location and direction of the sender, as well as proximity and relative-time between vehicles, to reduce the number of irrelevant messages verified (i.e., messages from vehicles that are unlikely to cause an accident). [PERSON] et al. [PERSON] et al. (2018) proposed a link Lifetime-aware Beacon-less Routing Protocol (LBRP) that is designed for large volume content delivery in VANETs. Each vehicle makes the forwarding decision based on the message header information and its current state, including the speed and position information. A semi-markov process analytical model is proposed to evaluate the expected delay in constructing one routing path for LBRP. While [PERSON] et al. (2018) discussed the applicability of several options to avoid the broadcast storm problem while trying to achieve the maximum coverage of the region of interest. Specifically, they have evaluated through simulations different ways to detect and take advantage of intersections and a strategy based on store-carry-forward to overcome short disconnections between groups of vehicles. [PERSON] et al. [PERSON] et al.