Roads in Thailand - Highway Numbering

Highway Numbering

The first digit of a highway number indicates the region of Thailand it primarily serves, with the number of digits indicating the highway classification. These regions are:

1. Northern Thailand.
2. Northeastern Thailand.
3. Central and Eastern, including the upper South.
4. Southern Thailand, except the upper South.

A single digit indicates one of four highways connecting Bangkok to outlying regions:

• Route 1 (Phahonyothin Road) to Northern Thailand
• Route 2 (Mittraphap Road) to Northeastern Thailand
• Route 3 (Sukhumvit Road) to Eastern Thailand
• Route 4 (Phetkasem Road) to Southern Thailand

Two digits indicate a principal highway within a region, such as Route 22 in the northeast between Udon Thani and Nakhon Phanom.

Three digits indicate a regional secondary highway, such as northeastern Route 202 between Chaiyaphum and Khemarat, and central Route 314 between Bang Pakong and Cha Choeng Sao.

Four digits indicate an intra-province highway connecting a provincial capital to its districts, or between important sites, such as northern Route 1001 between Route 11 Intersection and Amphoe Phrao, and southern Route 4006 between Route 4 Intersection (Ratchakrut) and Lang Suan.