## 2 Related Work  
Various researchers in the literature conducted performance analyses of various routing protocols in VANETs, with respect to several performance metrics. For instance, in the study [14], the performance results of seven different routing protocols were examined based on performance metrics such as packet delivery ratio, average throughput, delay and overall energy consumption. The authors highlighted that the performance of VANET routing protocol depends heavily upon the mobility model, the vehicle density and the propagation rate of data. The research [15] analyzed the throughput, packet delivery ratio (PDR), and normalized routing load (NRL) of AODV, DSR, and DSDV. The outcomes emphasize that AODV is more appropriate than DSR and DSDV in terms of PDR and throughput; however, the NRL for DSDV remains lower than AODV and DSR under different numbers of vehicles.  
The study [16] examined the performance of several routing protocols, including AODV, DSR, and DSDV, using different performance parameters, such as data throughput, PDR, end-to-end delay, and network stability. The authors stated that it is difficult to select a routing protocol that suits all requirements. They outlined that the efficiency of AODV protocol is better than DSR and DSDV protocols. In Ref. [17], the authors investigated the effect of traffic types (UDP and TCP) on AODV delay and throughput. They concluded that the traffic type UDP is better than TCP for safety applications and highlighted the necessity of implementing an improved version of AODV routing protocol. The researchersin [18] developed a new routing protocol labeled LENC (low-latency and energy-efficient routing based on network connectivity). Extensive simulations were conducted to compare AODV and the proposed routing protocol. Their findings outline the usefulness of LENC in providing more routing stability and the network connectivity. In [19], the authors proposed an enhanced version of a protocol based on cluster approach. The results prove that the proposed protocol outperforms CBCLR and AODV-CV protocols regarding throughput, packet delivery ratio, and end-to-end delay parameters while varying the number of vehicular nodes in the network. In the paper [20], researchers discussed the most important security features of the routing protocols in VANET and examined the effect of black hole attacks on AODV, along with attempting to introduce a mechanism to detect and prevent the network from such attacks. Similarly, the authors of paper [21] mitigated the impact of black hole attacka and vehicle density on the average throughput, packet delivery ratio, end-to-end delay, normalized routing load and average path length of AODV and ZRP routing protocols. They illustrated the vulnerability of these protocols to black hole attacks and recommended performing suitable solutions to mitigate the black hole attack in VANETs. In Ref. [22], the authors highlighted the high vulnerability of AODV to wormhole attacks. They proposed a practical approach for dealing with such attacks.  
In all the aforementioned studies, the common adopted approach relies on varying each factor individually, referred to as the OFAT approach (one factor at a time) [3]. The main problem of OFAT is that the number of experiments goes up as the number of studied factors increases. Furthermore, the OFAT approach does not allow direct comparisons of the magnitudes of each factor's impact on the investigated responses. In addition, it can neither estimate interactions among factors nor determine the optimal settings of factors.  
From the previous mentioned studies, we note that performance analysis studies based on the statistical design of experiments approaches have not gained much attention in the literature. Hence, the aim of the next section is to introduce its application to the assessment and the modeling of VANET routing protocols performances.