Abstract: Previous studies reported that the Qinghai-Tibet highway or railway had barrier effects on the migration of the Tibetan antelope (Pantholops hodgsonii) and other endemic species on the Tibetan Plateau. However, no study has focused on the overlapping barrier effect of those two transportation routes. Here, we analyzed the data of avoidance distance caused by road traffic disturbance of four typical ungulates in 2006-2008 and 2010  combined with field monitoring data during 2014 to 2019. Among the four species, there was an overlapping barrier effect only on the Tibetan antelope, the magnitude of which lessened with increased distance between the two transportation routes. The adaptation period (i.e., the amount of time it takes wildlife avoidance of the highway to reach a stable level) of Tibetan antelope along the highway was about four years, while the adaptation period for both Tibetan gazelle (Procapra picticaudata) and kiang (Equus kiang) was about two years. Traffic volume did not affect the avoidance distance of those four ungulates. A new expressway will be built parallel to the existing highway and railway. Based on existing knowledge, the distance between the expressway and the existing highway and railway should be at least 1.5 km to accommodate the migration of Tibetan antelopes. Although the four ungulate species could adapt to the presence of the highway, reducing human disturbance would still be beneficial. For example, creating undulating terrain and designing measures that screen vehicle lights and block traffic noise would help mitigate the impacts of expressway on the migration of Tibetan antelope. It is needed to monitor wildlife activity prior to, during, and after the construction of expressway.

Key words: barrier effect, road effect-zone, avoidance distance, overlapping effect, road ecology.