Construction Of Railways And Underground Railways

Details for Construction Of Railways And Underground Railways

SIC code 42120 is used for businesses carrying out activity in the field of construction of railways and underground railways. In plain English, it is likely to include contractors, trades, builders, installers, maintenance firms, developers and specialist construction service providers, with day-to-day activity often involving site work, project delivery, materials, labour, repairs, installations and compliance with building requirements. As of June 2026, 42120 ranks 250th out of 731 five-digit SIC codes, with 4,513 UK companies registered under it, making it a mid-tier classification used by a focused group of companies.

This sits within a classification system that has been used in the UK since the 1940s; Companies House filings moved from 4-digit SIC 2003 codes to the current 5-digit SIC 2007 scheme in 2008–2009, bringing the UK register into line with NACE Rev. 2. Companies are not limited to a single activity description: Companies House allows up to four SIC codes, so mixed businesses can show this work alongside complementary trading, advisory, production or support activities.

The short official label is deliberately compact, so the real-world businesses behind it may describe themselves using broader phrases such as construction of railways and underground railways services, specialist construction of railways and underground railways providers, operators in related supply chains, or companies supporting customers who need this form of commercial activity. For search and data work, the wording should be understood broadly: companies may use different everyday terms for the same activity, including trade names, sector jargon, abbreviated service descriptions and customer-facing language. The code therefore works best as a structured indicator of economic activity rather than a complete profile of the company, because many organisations evolve, add services or reorganise after incorporation.

Taken together with location, age, filing history and other SIC selections, this code can help build a more rounded view of the market in which the company appears to operate. In practical terms, the code helps separate this kind of work from neighbouring sectors that may look similar in search results but involve different trading models, assets, customers or regulatory expectations.

Our Recently Formed marketing database is updated daily on the previous days company activity at Companies House to allow you to find new companies quickly and easily (whereas this categorised page of data counts is updated monthly). We provide the widest choice of filters available for Recently Formed Companies. And its not just Newly Formed companies - We have over 4 million companies - from new starters to companies over 100 years old, able to be filtered geographically or by category, but if you are looking to get in touch with companies within this category, the below table shows how many companies were added to the category, month by month over the last couple of years.