1948 Locomotive Exchange Trials
The 1948 Locomotive Exchange Trials were organised by the newly nationalised British Railways (BR). Locomotives from the former "Big Four" constituent companies (GWR, LMS, LNER, SR) were transferred to and worked on other regions. Officially, these comparisons were to identify the best qualities of the four different schools of thought of locomotive design so that they could be used in the planned BR standard designs. However, the testing had little scientific rigour, and political influence meant that LMS practice was largely followed by the new standard designs regardless. However, the trials were useful publicity for BR  to show the unity of the new British Railways. To record the locomotive performances, one of three dynamometer cars were included in the consist directly behind the locomotive (with a GWR, LMS and NER version being available). LMS engines which operated over the Southern Region, where there were no water troughs, were paired with four-axled ex-WD tenders with larger water tanks. These were specially given LMS lettering for the occasion. Similarly, ex-Southern types used elsewhere were paired with ex-LMS tenders with water scoops. Locomotives used were as follows (NB numbers given should be the ones carried  at the time, so this is a somewhat curious mixture of old pre-nationalisation numbers, prefixed numbers, and new BR numbers): Express passenger locomotives. The four routes used were: LMS Euston to Carlisle, LNER Kings Cross to Leeds, GWR Paddington to Plymouth, and SR Waterloo to Exeter. The only line with a loading gauge of sufficient size to take a GWR King was the LNER main line out of Kings Cross, meaning that the class was limited to that line only. Official test runs on the LNER East Coast Main Line were held on the following dates, using the NER  Dynamometer Car: Official test runs on the LMS West Coast Main Line were held on the following dates, using the L&YR Dynamometer Car whilst hauling the "Royal Scot": Official test runs on the SR West of England Main Line were held on the following dates, using the GWR Dynamometer Car whilst hauling the "Atlantic Coast Express": Official test runs on the GWR Main Line were held on the following dates, using the GWR Dynamometer Car: Mixed Traffic locomotives. The four routes used were: Midland Main Line St. Pancras to Manchester, Great Central Main Line Marylebone to Manchester, Highland Main Line  Perth to Inverness, and South Devon Main Line Bristol to Plymouth. Official test runs on the South Devon Main Line were held on the following dates, using the GWR Dynamometer Car: Official test runs on the Midland Main Line were held on the following dates, using the L&YR Dynamometer Car: Official test runs on the Great Central Main Line were held on the following dates, using the NER Dynamometer Car: Official test runs on the Highland Main Line were held on the following dates, using the NER Dynamometer Car: Freight locomotives. The four routes used were: London Midland Region Brent  to Toton, Eastern Region Ferme Park (London) to New England (Peterborough), Western Region Acton (London) to Severn Tunnel Junction (South Wales), and Southern Region Bristol to Eastleigh. Due to the tests being held on non-public services, details are only available from the Official Report. Eastern Region tests were carried out using the L&YR Dynamometer Car by: Western Region tests were carried out using the NER Dynamometer Car by: Midland Region tests were carried out by: Southern Region tests were carried out by: