The development of virtual reality (VR) technologies offers high expectations for growth in the coming years. The massive increase in the use of virtual environments will lead to a high consumption of resources, making it necessary to ensure their sustainability. Taking this scenario into account, this paper focuses on analyzing and comparing the sustainability of the two variants of VR, immersive virtual reality (IVR) and non-immersive virtual reality (NIVR). To achieve this goal, the different areas of sustainable development that are influenced by these technologies have been identified (economy, society and environment). From the results obtained, it can be stated that VR technology is advantageous for all three areas of sustainable development analyzed from three main points of view: (i) as an emerging technology that allows energy costs to be reduced and encourage economic activity with low environmental impact; and (ii) as a teaching resource in higher education, such as engineering, because it allows the design of dynamic and interactive learning environments, which facilitate the understanding of certain concepts. In the case of economic and social areas, especially those related to education, it is the areas of sustainable development in which these differences are most noticeable. In this research, an experience is carried out with engineering students where it is shown that students perceive the RVI as more interactive than the RVNI, but that this perception does not lead to an increase in the academic performance of the students. On the contrary, in the professors' opinion, the impression caused by the IVR on the students could lead them to divert their attention to certain recreational or interactive aspects of the activity that do not have an impact on their learning. Keywords: immersion, virtual reality, development, sustainable technologies, virtual environments.

Emission reduction and energy efficiency are fundamental objectives for the sustainability of the urban transport (UT) sector. One of the actions to achieve these objectives is to replace the vehicles that make up the fleet of UT buses with more efficient ones, equipped with regenerative braking systems that allow the recovery of part of the energy used in travel. However, sometimes the total replacement of the fleet of UT buses is not feasible and only a partial replacement of the fleet is possible. The present study proposes a mathematical model of easy application to compare different UT routes and to locate the greatest improvement niches. The contributions of the proposed model focus on several aspects: (i) optimizing economic resources; (ii) allocating the most efficient equipment where energy consumption can be most optimized; and (iii) simplifying the task of optimizing passenger transport routes. Thanks to the proposed model, the 6 UT lines of the city of Ávila can be classified in order to maximize efficiency in a possible partial renewal of the fleet.