Intelligent transport systems (ITSs) play a key role in people's daily activities. ITSs significantly improve mobility offering a variety of services to a vast number of users that increase on a daily basis, as more and new services are introduced. These services are based on advanced information and communication technologies (ICTs) and rely strongly on connectivity and computing resources. However, technical vulnerabilities of the technologies used in ITS, as well as the increase in users' awareness has brought security and privacy concerns to the forefront. This article aims at identifying a set of privacy concepts that provide the bases for designing trustworthy ITS services identifying possible threats and users' privacy concerns. A key contribution of the article is a roadmap that presents in detail how for every ITS function corresponding to privacy concepts can be realized for overcoming specific threats and users' privacy concerns in a smart city context.