Telent Technology Services has won a record contract worth more than £100 million as part of a major award from Transport for London (TfL).
The Warwick-based firm, which specialises in communication infrastructure, is part of a three-supplier, eight-year agreement which will see the capital's 6,000 traffic signals upgraded and maintained.
It will supply, install and maintain all traffic control equipment in the west and south west of London, making it responsible for 49 per cent of the city's entire traffic signal estate.
Telent said its brief was believed to be the largest single traffic signal supply and maintenance contract ever awarded in the UK.
The firm will also help expand the use of intelligent traffic signals, as well as new crossings for pedestrians and cyclists.
Managing director Chris Metcalfe said: "Winning this contract is a tremendous moment for Telent and builds on our growing capability and reputation for world class levels of commitment, support and know-how.
"It positions us as a key technology services supplier to TfL's surface transport directorate in what is undoubtedly a flagship contract anywhere within the urban traffic industry.
"It is also a great acknowledgement for our people, who have tremendous pride and dedication in what they do, their individual efforts and track record have all contributed to making this possible."
TfL said the contracts were part of a doubling of the investment into London's road network - from £2 billion to £4 billion - and the contracts would deliver a saving of around £42 million compared to other contracts.