| Rank | Country | dual gauge | Railways |
| Philippines | | total: 897 km narrow gauge: 897 km 1.067-m gauge (492 km are in operation) (2006) |
| Pitcairn Islands | | void |
| Poland | | total: 23,072 km broad gauge: 629 km 1.524-m gauge standard gauge: 22,443 km 1.435-m gauge (20,555 km operational; 11,910 km electrified) (2006) |
| Portugal | | total: 2,786 km broad gauge: 2,603 km 1.668-m gauge (1,351 km electrified) narrow gauge: 183 km 1.000-m gauge (2006) |
| Puerto Rico | | total: 96 km narrow gauge: 96 km 1.000-m gauge (2006) |
| Qatar | | void |
| Romania | | total: 11,385 km broad gauge: 60 km 1.524-m gauge standard gauge: 10,898 km 1.435-m gauge (3,888 km electrified) narrow gauge: 427 km 0.760-m gauge (2006) |
| Russia | | total: 87,157 km broad gauge: 86,200 km 1.520-m gauge (40,300 km electrified) narrow gauge: 957 km 1.067-m gauge (on Sakhalin Island) note: an additional 30,000 km of non-common carrier lines serve industries (2006) |
| Rwanda | | void |
| Saint Barthelemy | | void |
| Saint Helena | | void |
| Saint Kitts and Nevis | | total: 50 km narrow gauge: 50 km 0.762-m gauge on Saint Kitts for tourists (2006) |
| Saint Lucia | | void |
| Saint Martin | | void |
| Saint Pierre and Miquelon | | void |
| Saint Vincent and the Grenadines | | void |
| Samoa | | void |
| San Marino | | void |
| Sao Tome and Principe | | void |
| Saudi Arabia | | total: 1,392 km standard gauge: 1,392 km 1.435-m gauge (with branch lines and sidings) (2006) |
| Senegal | | total: 906 km narrow gauge: 906 km 1.000 meter gauge (2006) |
| Serbia | | total: 3,379 km standard gauge: 3,379 km 1.435-m gauge (electrified 1,254 km) (2006) |
| Seychelles | | void |
| Sierra Leone | | void |
| Singapore | | void |
| Slovakia | | total: 3,662 km broad gauge: 100 km 1.520-m gauge standard gauge: 3,512 km 1.435-m gauge (1,588 km electrified) narrow gauge: 50 km (1.000-m or 0.750-m gauge) (2006) |