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 train 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):
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.[2]
Official test runs on the LNER East Coast Main Line were held on the following dates, using the NER Dynamometer Car:
28 May, hauled by LNER Class A4 60034 Lord Faringdon in the up direction
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:
25 June, hauled by GWR Modified Hall Class 6990 Witherslack Hall in the up direction
Official test runs on the Highland Main Line were held on the following dates, using the NER Dynamometer Car:
13 July, hauled by SR West Country class 34004 Yeovil in the down direction
14 July, hauled by SR West Country class 34004 Yeovil in the up direction
14 July, hauled by LMS Black Five 44799 in the down direction (on scheduled service, 1155am ex-Perth)
20 July, hauled by LNER Class B1 61292 in the down direction
21 July, hauled by LNER Class B1 61292 in the up direction
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.[1] 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: