separately. Probably, there is limited RL data used in UL study because in UL studies, the separation ofRL transport is not easy to capture; moreover, decisions that affect production of RL data might not beconsidered as important as UL data. Due to that, a discussion about the main characteristics of theresearch on both areas was carried out, based upon the researchers’ experience and several literaturereviews recently published on both topics, in order to provide a description of the main challengesthey will face in a near future. As a result, some useful insights are provided in the following section.