| South Houston to Popovo | 6,179.20 mi (9,944.46 km) |
| South Houston to Provadia | 6,231.45 mi (10,028.55 km) |
| South Houston to Radnevo | 6,216.51 mi (10,004.51 km) |
| South Houston to Radomir | 6,090.30 mi (9,801.40 km) |
| South Houston to Rakitovo | 6,159.81 mi (9,913.26 km) |
| South Houston to Rakovski | 6,180.08 mi (9,945.88 km) |
| South Houston to Razgrad | 6,181.20 mi (9,947.69 km) |
| South Houston to Razlog | 6,140.21 mi (9,881.72 km) |
| South Houston to Ruse | 6,146.92 mi (9,892.51 km) |
| South Houston to Samokov | 6,123.38 mi (9,854.63 km) |
| South Houston to Sandanski | 6,147.03 mi (9,892.70 km) |
| South Houston to Sevlievo | 6,152.06 mi (9,900.78 km) |
| South Houston to Shumen | 6,208.29 mi (9,991.28 km) |
| South Houston to Silistra | 6,181.19 mi (9,947.66 km) |
| South Houston to Sliven | 6,213.88 mi (10,000.28 km) |
