Slope Instability as aThreatening Factor of Traffic Accidents Case Study: Landslide in Nir- Sarab Road of Ardebil Province in Northwest Iran

There are many environmental hazards that arise from slope instability, and commonly disrupt or damage transportation systems at a variety of spatial and temporal scales. One of these cases is a Landslide in Nir-Sarab road that disturbed 480 m of the road in June 8, 2005. This landslide has a compositional structure (rotational slump at the crown and earthflow in the toe). All of four groups of destabilizing factors of preconditional preparatory, triggering, and sustaining factors influenced the landslide occurring in Nir-Sarab road. Scarps, debris cones, fractures, landslide dams are geomorphologic results of this landslide. Results of this study indicate that in road lines such as Saeen pass (Nir-Sarab road) that cross active geomorphologic zones, engineering activities such as road construction may cancel the geomorphologic balance and produce.