The official SPA news agency on Saturday reported that the French consulting firm Semaly and the Middle East engineering firm Dar al-Handasah were granted the $2.1 million contract, stretching for a period of 14 months.
"The studies will assess the situation on the ground with respect to the social, economic and environmental impact of the project on the capital," SPA quoted Tariq al-Faris, vice-president of the Projects Centre at the Riyadh Development Authority as saying.
The studies will also assess technical needs in terms of locating suitable paths for installing the tracks within the city, Faris added.
Saudi Arabia has embarked on a major plan to increase the use of railways between the cities of its kingdom.
The multi-billion dollar expansion programme includes a 950km loop from Riyadh to Jeddah on the Red Sea, joining existing lines from the capital to the oil city of Dammam on the Gulf.
A 570km line between Makka, Madina and Jidda and extending north to the industrial city of Yanbu is also planned to ease the travel of some two million pilgrims who visit Muslim holy sites during the annual pilgrimage.