With a length of 167.10 km (103.83 mi), it connects the capital of Phnom Penh, through Prey Veng Province, with Bavet, Svay Rieng Province on the border with Vietnam, and continues in Vietnam as the QL22 Highway to Ho Chi Minh City in the south east.

[2] Originally constructed during French colonial times, National Highway 1 is an important link from Phnom Penh to Ho Chi Minh City, formerly Saigon.

[3] In 1981, Cambodia opened a newly repaired section of National Highway 1 to the Vietnamese border.

[4] The NH 1 starts in Phnom Penh, the capital of Cambodia, where it joins the National Highway 5 at Stat Chas Circle Garden, near the French Embassy.

The road ends at the Border Check Point in Bavel, Svay Rieng Province, and on the Vietnamese side, it continues as the QL22 highway to Ho Chi Minh City.