The 1948 Locomotive Exchange Trials were organised by the newly nationalised British Railways. Locomotives from the former "Big Four" constituent companies 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. LMS engines 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 :
3 June, hauled by SR Merchant Navy Class 35018 British India Line in the down direction
4 June, hauled by SR Merchant Navy Class 35018 British India Line in the up direction
8 June, hauled by LNER Class A4 E22 Mallard in the down direction
10 June, hauled by LNER Class A4 60033 Seagull in the down direction
11 June, hauled by LNER Class A4 60033 Seagull in the up direction
17 June, hauled by LMS Rebuilt Royal Scot Class 46154 The Hussar in the down direction
18 June, hauled by LMS Rebuilt Royal Scot Class 46154 The Hussar in the up direction
24 June, hauled by LMS Coronation Class 46236 City of Bradford in the down direction
25 June, hauled by LMS Coronation Class 46236 City of Bradford in the up direction
Official test runs on the GWR Main Line were held on the following dates, using the GWR Dynamometer Car:
27 April, hauled by SR Merchant Navy Class 35019 French Line C.G.T in the down direction
28 April, hauled by SR Merchant Navy Class 35019 French Line C.G.T in the up direction
4 May, hauled by LNER Class A4 60033 Seagull in the down direction
5 May, hauled by LNER Class A4 60033 Seagull in the up direction
18 May, hauled by LMS Coronation Class 46236 City of Bradford in the down direction
19 May, hauled by LMS Coronation Class 46236 City of Bradford in the up direction
25 May, hauled by LMS Rebuilt Royal Scot Class 46162 Queens Westminster Rifleman in the down direction
26 May, hauled by LMS Rebuilt Royal Scot Class 46162 Queens Westminster Rifleman in the up direction
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:
7 July, hauled by LNER Class B1 61251 Oliver Bury in the up direction
14 July, hauled by LMS Black Five 45253 in the up direction
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
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 RegionBrent to Toton, Eastern Region Ferme Park to New England, Western Region Acton to Severn Tunnel Junction, 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:
