SIC code 42120 covers construction of railways and underground railways activities in the UK, with 2,578 active companies currently registered. It falls under Section F (Construction) of the UK SIC 2007 classification system. The average company age is 6.5 years.
SIC code 42120 stands for "Construction of railways and underground railways" under the UK Standard Industrial Classification (SIC 2007) system. It belongs to Section F — Construction. Companies use this code when registering with Companies House to indicate their primary business activity.
There are currently 2,578 active companies registered under SIC code 42120 in the UK, out of 3,893 total registrations (including dissolved companies).
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Data sourced from Companies House, HM Land Registry, FCA Register, and 50+ government databases. SIC classification follows the UK Standard Industrial Classification of Economic Activities 2007 (SIC 2007). Last updated: 2026-04-05.