Vehicular ad-hoc networks (VANETs) significantly enhance transportation efficiency, accident prevention, and pedestrian comfort by facilitating seamless information exchange between vehicles and road infrastructure. The effective deployment of VANETs depends on the precision of message delivery with minimal latency, along with data security and privacy protections. Reflecting this focus, numerous researchers have undertaken studies and surveys presenting various models and solutions that enhance VANET across different aspects. This study offers a comprehensive survey of VANETs, detailing specific applications, and presenting an integrated view of current challenges and future directions. This paper makes several key contributions: Firstly, it explore the types of communication in VANETs. Secondly, it provides a complete taxonomy of VANET applications in Intelligent Transportation System (ITS). Thirdly, it introduces a detailed taxonomy of VANET challenges in ITS, discussing these challenges within the contexts of applications, data networking, and resource management in VANET. Finally, it explores future directions in details, addressing ongoing research challenges. This survey provides researchers with an in-depth understanding of each technology within VANETs, outlining the challenges, solutions, and recommendations for further advancements. This study assists researchers in the vehicular networking domain in selecting proposals based on their relative advantages.