The British Rail Research Division was a division of the state-owned railway company British Rail (BR). It was charged with conducting research into improving various aspects of Britain's railways, particularly in the areas of reliability and efficiency, including achieving cost reductions and increasing service levels.

Its creation was endorsed by the newly created British Rail Board (BRB) in 1963 and incorporated personnel and existing resources from all over the country, including the LMS Scientific Research Laboratory. It was primarily based at the purpose-built Railway Technical Centre in Derby. In addition to its domestic activities, the Research Division would provide technology and personnel to other countries for varying purposes and periods under the trade name "Transmark". It became recognised as a centre of excellence in its field; the theoretical rigour of its approach to railway engineering superseded the ad hoc methods that had prevailed previously.

Its research led to advances in various sectors, such as in the field of signalling, where progress was made with block systems, remote operation systems, and the Automatic Warning System (AWS). Trackside improvements, such as the standardisation of overhead electrification equipment and refinements to the plasma torch, were also results of the Research Division's activities. Perhaps its most high-profile work was into new forms of rolling stock, such as the High Speed Freight Vehicle and railbuses, which led to the introduction of the Class 140. One of its projects that gained particularly high-profile coverage was the Advanced Passenger Train (APT), a high-speed tilting train intended for BR's Intercity services. However, due to schedule overruns, negative press coverage, and a lack of political support, work on the APT was ceased in the mid-1980s in favour of the more conventional InterCity 125 and InterCity 225 trainsets.

The Research Division was reorganised in the runup to the privatisation of British Rail during the 1990s; the bulk having become "BR Research Limited". This unit was acquired by the private company AEA Technology in 1996, which has since become Resonate Group. Several elements of its work have continued under various organisations, such as the patents filed during the APT's development being harnessed in the development of the Pendolino, a modern high speed tilting train.

During the mid-1950s, it became increasingly apparent to senior figures within the British Transport Commission (BTC) that, in light of mixed results from using external contractors, there was value in British Rail performing some research projects in-house instead. In August 1958, Dr F. T. Barnwell was appointed by the BTC to prepare and present specific electrical research proposals; the creation of an initially small Electrical Research Section employing 31 staff was also authorised by the BTC in July 1960. Many of these early proposals were related to traction and power equipment, such as motor control, signalling, digital computers, and 25 kV AC railway electrification. Several existing research efforts, such as into rail adhesion, were also folded into the new section's remit; in June 1960, the Rugby Locomotive Testing Senter was also transferred to the Chief Electrical Engineer's responsibility and became a key site for the section.

During 1963, the newly created British Rail Board (BRB) agreed to transfer the Electrical Research Section to the British Rail Research Department, with the purpose of forming a completely new division. The Research Division brought together personnel and expertise from all over the country, including the LMS Scientific Research Laboratory. Its remit was not simply the improvement of existing equipment, or the solution of existing problems, but fundamental research from first principles, into railway operation. The results of its work would go on to inform development by engineers, manufacturers and railways all over the world. For instance, once the initial APT-E experimental project was complete, it passed to the mechanical engineering department to build the APT-P prototype. In time, engineers would be seconded to other countries for varying periods under the trade name "Transmark".

One early matter for this new division was the choice for a long term location, Rugby being passed over in favour of Derby, where the purpose-built Railway Technical Centre was built during the 1960s at a cost of £4 million. Nearby, the Research Division developed its first test track on the old Great Northern Railway line between Egginton Junction and Derby Friargate (later used only as far as Mickleover) and was used by the Train Control Group. Later on, when the revolutionary Advanced Passenger Train (APT) was being developed, a second test track was created on the line between Melton Junction and Edwalton (known as the Old Dalby Test Track), which was acquired specifically to test this train. The Mickleover test track was closed and lifted in the early 1990s, however Old Dalby remained in use into the twenty-first century.

Early benefits of the Research Division's work were already being felt by the late 1960s in the field of signalling, specifically in block systems. While practical demonstrations were being performed as early as 1964, some of these efforts, such as an early use of radar-based obstacle detection, proved to be not mature enough for deployment. One project of this nature that was highly impactful on future railway operations was the creation of automated simulations of traffic flow through a network. In response to concerns by managers of the British Rail's Southern Region, the Research Team developed improvements for the Automatic Warning System (AWS), sometimes referred to as Signal Repeating AWS, which would be deployed extensively in that region. Another early advance was the remote control of freight locomotives at low speed, such as when coal trains were delivering their materials to power stations.