In the former Soviet Union the total length of gas mains increased constantly by about 8300 km per year in the period 1981–1990 and reached 207 000 km by early 1990. The major part of this network comprises of large diameter pipelines (e.g. d>20″). During this decade, the biggest gas pipelines of 56″ diameter were constructed and put into service linking the gas fields of West Siberia to European regions.