The move seeks to ease business and leisure travel for Kazakhstani citizens and to open up the nation's economy.
Bus travel between the two neighbouring countries has restarted after a 17-year hiatus.
The bus service aims to increase citizens' mobility and open the doors for improved bilateral relations.
An upcoming Tashkent summit of the two countries' presidents could determine the fate of the railway project, say observers.
The Turkmenistan-Afghanistan-Tajikistan (TAT) railway has already brought a number of Turkmen commodities to Afghan markets.
A vital new corridor opened June 22.