For cities to utilise their maximum liveability potential, their transport infrastructure and overall service provision need to function seamlessly. To this end, urban street eco-systems should be characterised, organised and utilised effectively. But is this happening on a mass scale across the globe? Are our urban street classification schemes forward-thinking and ready to respond to the emerging sustainability and resilience challenges cities face nowadays? This paper aims to answer these questions by examining and decoding the prevailing "formal street classification scheme model" through conducting a detailed worldwide review of formal national street classification plans. Out of 196 countries investigated, 128 official street classification plans were identified, analysed and evaluated. We also used an Analytical Hierarchy Process (AHP) with 20 experts coming from different fields (i.e., academics, policymakers, practitioners) to enhance our results and contribute to developing an index evaluating urban street classification under the prism of sustainability. The outcomes of our work signify that conventional pro-automobile approaches still prevail, thus shaping car-centric conditions, which undermine the role of sustainable modes and reduce the ability of cities to innovate and succeed. It is demonstrated that the road to achieve sustainability and completeness in urban transport systems, considering these car-led plans, is still uphill. Based on that, multi-dimensional classification systems prioritising public and active transport, while appreciating street's urban aspect should be promoted in the future.