Purpose - The purpose of this paper is to refine a logistics triad uncertainty model taking a supply chain perspective, to determine and assess the different causes and sources of supply chain uncertainty that impact on the sustainability of the UK road freight transport sector. Design/methodology/approach - To clarify the link between sustainability and transport uncertainty, a methodological triangulation strategy is applied combining the results of eight focus groups and an online structured questionnaire. Findings - The findings indicate that the main drivers impacting the sustainability of transport operations are delays, variable demand/poor information, delivery constraints and insufficient supply chain integration. The consequence of these problems is to reduce the efficiency of transport operations. Research limitations/implications - The model has been refined based only on participants' perceptions. Therefore, the finding should also be verified through the investigation of real-world situations. Moreover, the transport uncertainty model needs to be incorporated within a wider business process re-engineering approach to evaluate solutions to reduce transport uncertainty within supply chains. Practical implications - The findings further strengthen the understanding of the main uncertainty sources within supply chains in the UK. The internal root causes of uncertainty can be mitigated while external issues have to be accommodated; therefore, mitigation techniques, methods and strategies for reducing external and internal supply chain uncertainty in transport operations need to be identified through the research. Originality/value - This paper determines the industry perceived economic and environmental risks associated with transport operations in four UK sectors. [PUBLICATION ABSTRACT]