| Rank | Country | dual gauge | Railways |
| Jersey | | void |
| Jordan | | total: 507 km narrow gauge: 507 km 1.050-m gauge (2010) |
| Kazakhstan | | total: 15,079 km broad gauge: 15,079 km 1.520-m gauge (4,000 km electrified) (2010) |
| Kenya | | total: 2,066 km narrow gauge: 2,066 km 1.000-m gauge (2010) |
| Kiribati | | void |
| Korea, North | | total: 5,242 km standard gauge: 5,242 km 1.435-m gauge (3,500 km electrified) (2009) |
| Korea, South | | total: 3,381 km standard gauge: 3,381 km 1.435-m gauge (1,843 km electrified) (2008) |
| Kosovo | | total: 430 km standard gauge: 430 km 1.435-m gauge (2007) |
| Kuwait | | void |
| Kyrgyzstan | | total: 470 km broad gauge: 470 km 1.520-m gauge (2010) |
| Laos | | void |
| Latvia | | total: 2,239 km broad gauge: 2,206 km 1.520-m gauge narrow gauge: 33 km 0.750-m gauge (2010) |