| Rank | Country | dual gauge | Railways |
| Ireland | | total: 3,237 km broad gauge: 1,872 km 1.600-m gauge (37 km electrified) narrow gauge: 1,365 km 0.914-m gauge (operated by the Irish Peat Board to transport peat to power stations and briquetting plants) (2006) |
| Isle of Man | | total: 65 km standard gauge: 7 km 1.067-m gauge (7 km electrified) narrow gauge: 58 km 0.914-m gauge (29 km electrified) note: primarily summer tourist attractions (2006) |
| Israel | | total: 853 km standard gauge: 853 km 1.435-m gauge (2006) |
| Italy | | total: 19,460 km standard gauge: 18,038 km 1.435-m gauge (11,354 km electrified) narrow gauge: 123 km 1.000-m gauge (123 km electrified); 1,299 km 0.950-m gauge (161 km electrified) (2006) |
| Jamaica | | void |
| Jan Mayen | | void |
| Japan | | total: 23,474 km standard gauge: 3,204 km 1.435-m gauge (3,204 km electrified) narrow gauge: 77 km 1.372-m gauge (77 km electrified); 20,182 km 1.067-m gauge (13,334 km electrified); 11 km 0.762-m gauge (11 km electrified) (2006) |
| Jersey | | void |
| Jordan | | total: 505 km narrow gauge: 505 km 1.050-m gauge (2006) |
| Kazakhstan | | total: 13,700 km broad gauge: 13,700 km 1.520-m gauge (3,700 km electrified) (2006) |
| Kenya | | total: 2,778 km narrow gauge: 2,778 km 1.000-m gauge (2006) |
| Kiribati | | void |
| Korea, North | | total: 5,235 km standard gauge: 5,235 km 1.435-m gauge (3,500 km electrified) (2006) |
| Korea, South | | total: 3,472 km standard gauge: 3,472 km 1.435-m gauge (1,342 km electrified) (2006) |
| Kosovo | | total: 430 km (2005) |
| Kuwait | | void |
| Kyrgyzstan | | total: 470 km broad gauge: 470 km 1.520-m gauge (2006) |
| Laos | | void |
| Latvia | | total: 2,303 km broad gauge: 2,270 km 1.520-m gauge (257 km electrified) narrow gauge: 33 km 0.750-m gauge (2006) |
| Lebanon | | total: 401 km standard gauge: 319 km 1.435 m narrow gauge: 82 km 1.050 m note: rail system became unusable because of damage done during fighting in the 1980s and in 2006 (2006) |
| Lesotho | | void |