Date | Section of line | Broad | Mixed |
| 1 Jan 1857 | Total mileage | 663m 46c | 156m 24c |
| 20 Jan 1857 | Yeovil - Weymouth | 20m 66c | 6m 49c |
| ? Feb 1857 | Branch to Swansea Vale Railway3 | 0m 30c | |
| 2 Feb 1857 | Bradford Junction - Bathampton | 9m 12c | |
| 2 Feb 1857 | Yeovil Henford Junction - Pen Mill1 | 1m 38c | |
| 1 Jun 1857 | Twyford - Henley | 4m 47c | |
| 1 Jun 1857 | Nantmelyn Colliery - Bwllfa Dare Colliery4 | 0m 34c | |
| 1 Jul 1857 | Holt Junction - Devizes | 8m 17c | |
| 12 Nov 1857 | Maiden Newton - Bridport | 9m 21c | |
| 19 Apr 1858 | Cardiff Bute Docks branch3 | 1m 19c | |
| 3 May 1858 | Highbridge - Burnham5 | 1m 43c | |
| 9 Nov 1858 | Witham - Shepton Mallet2 | 9m 3c | |
| 15 Mar 1859 | Glastonbury - Wells5 | 5m 28c | |
| 4 May 1859 | Plymouth - Truro10 | 53m 39c | |
| 1 Jun 1859 | Wednesbury branch | 0m 14c | |
| 22 Jun 1859 | Tavistock Junction - Tavistock6 | 12m 71c | |
| 18 Jul 1859 | Southall - Brentford | 3m 77c | |
| ? Aug 1859 | Bridgwater Docks branch1 | 0m 48c | |
| 2 Aug 1859 | Torre - Paignton6 | 2m 78c | |
| ? Sep 1859 | Swansea North Dock branch3 | 0m 22c | |
| 1 Mar 1860 | Myrtle Hill Jctn - Carmathen8 | 1m 5c | |
| 2 Aug 1860 | Llantrissant - Tonyrefail | 4m 77c | |
| 3 Sep 1860 | Carmarthen - Conwil8 | 6m 1c | |
| 10 Oct 1860 | Hatton - Stratford-on-Avon | 9m 75c | |
| 14 Mar 1861 | Paignton - Churston6 | 2m 72c | |
| ? Jun 1861 | Briton Ferry Jctn - Tonmawr Tunnel9 | 5m 64c | |
| 10 Aug 1861 | Bridgend - Duffryn Llynvi7 | 10m 11c | |
| 10 Aug 1861 | Tondu - Porthcawl Harbour7 | 9m 58c | |
| 23 Aug 1861 | Briton Ferry Dock branch4 | 0m 45c | |
| 31 Aug 1861 | Somerset Central Railway to standard gauge | 19m 29c - | |
| 1 Oct 1861 | Reading - London Padington (mixed) | 36m 78c - | 36m 78c |
| 1 Oct 1861 | Southall - Brentford (mixed) | 3m 77c - | 3m 77c |
| 1 Nov 1861 | Bordesley Junction branch | 0m 21c | |
| 31 Dec 1861 | Total mileage | 790m 8c | 214m 18c |
| Metric conversion: 80 chains = 1 mile; 5 miles = 8 kilometres | |||
| Note 1: | Bristol & Exeter Railway | ||
| Note 2: | East Somerset Railway | ||
| Note 3: | South Wales Railway | ||
| Note 4: | Vale of Neath Railway | ||
| Note 5: | Somerset Central Railway | ||
| Note 6: | South Devon Railway | ||
| Note 7: | Llynvi & Ogmore Railway | ||
| Note 8: | Carmarthen & Cardigan Railway | ||
| Note 9: | South Wales Mineral Railway | ||
| Note 10: | Cornwall Railway | ||
Locomotive Class | No. (+/-) | Total | |
| 1 Jan 1857 | Total locomotives | 367 | |
| Star 2-2-2 | 12 | ||
| Fire Fly 2-2-2 | 62 | ||
| Sun 2-2-2 | 21 | ||
| Leo 2-4-0 | 18 | ||
| Hercules 0-6-0 | 4 | ||
| Great Western 4-2-2 | 1 | ||
| Prince 2-2-2 | 6 | ||
| Iron Duke 4-2-2 | 29 | ||
| Avalanche 0-6-0T | 1 | ||
| Premier 0-6-0 | 12 | ||
| Pyracmon 0-6-0 | 6 | ||
| Bacchus 0-6-0 | 1 | ||
| Bogie 4-4-0T | 15 | ||
| Waverley 4-4-0 | 10 | ||
| Victoria 2-4-0 | 8 | ||
| Ceasar 0-6-0 | 8 | ||
| Banking 0-6-0T | 4 | ||
| Standard Goods 0-6-0 | +30 | 90 | |
| B&ER 4-2-2 | 20 | ||
| B&ER 0-6-0 | + 2 | 18 | |
| B&ER 4-2-4T | 4 | ||
| B&ER 4-4-0T | 6 | ||
| B&ER 2-2-2T | + 2 | 7 | |
| VofNR 4-4-0T | 9 | ||
| VofNR 0-6-0T | + 5 | 10 | |
| SDR 4-4-0T | + 12 | 24 | |
| SDR 0-6-0T | + 4 | 8 | |
| CCR 4-4-0T | + 2 | 2 | |
| Unclassified engines | 8 | ||
| 31 Dec 1861 | Total locomotives | +57 | 424 |
| Key: | B&ER - Bristol & Exeter Railway VofNR - Vale of Neath Railway SDR - South Devon Railway CCR - Carmathen & Cardigan Railway | ||