In the concept design stage of transportation projects; design services such as  corridor study, determination of the required performance characteristics of the mode of transport based on transportation modelling; definition of criteria such as the number of rolling stock, headway, etc. in metro systems and verifying them with operational simulations; determination of the number of lanes on motorways and state roads and types of interchanges; selection of the criteria to be used in transportation projects in accordance with the performance objectives of the project are carried out.


In the preliminary design stage of transportation projects, design standards that will ensure the performance objectives determined during the concept design process are optimized, and in accordance with the environmental conditions, taking into account the criteria such as economy, functionality and aesthetics, a design where approximate costs for assessment purpose at pre-final stage, are put forward before final design.