National Road 4 upgrade reaches 100% physical progress

What the NR4 upgrade was designed to improve

National Road 4 is the long-established road corridor between the Phnom Penh area and Sihanoukville, continuing toward Cambodia’s main deep-sea port. The project corridor passes through Kandal, Kampong Speu, Koh Kong and Preah Sihanouk provinces, making it important for local access as well as longer-distance passenger and freight traffic.

The NR4 works were added to the World Bank-backed Road Asset Management Project II through a $110 million additional financing package approved in 2018. The design covered asphalt-concrete resurfacing, paved shoulders, stronger pavement in vulnerable sections, drainage, cross-drainage structures and bridge works. Flood resilience and road safety were built into the programme because heavy rainfall and water damage had been identified as material risks along parts of the route.

The ministry’s June update referred specifically to 100% physical progress. That is a narrower statement than saying every contract, payment, maintenance obligation or administrative step under the wider programme has been completed.

For practical context, see Cambodia market and country comparisons. This development also connects with Cambodia vehicle tax: 30 November 2026 payment deadline.

NR4 still serves a different role from the expressway

Cambodia also has the separate Phnom Penh-Sihanoukville Expressway, a roughly 187 km toll road that opened to traffic in 2022. It is a controlled-access route intended for faster through travel between the capital and Sihanoukville.

NR4 remains the road people use when they need direct access to towns, businesses, industrial sites and connecting roads along the corridor. For residents and companies based between the two endpoints, the difference is practical: the expressway can bypass many intermediate places, while NR4 forms part of the local road network itself.

Finishing the main rehabilitation works should remove construction activity as a persistent feature of the project corridor. It does not, by itself, establish a new door-to-door travel time, so any claim about minutes saved would need separate traffic data after completion.

The World Bank project is still formally active

As of September 22, the World Bank continued to list KH - Road Asset Management Project II (P150572) as active, with a closing date of December 31, 2026. The status is consistent with a project that can finish major civil works before all programme-level tasks and close-out steps are complete.

The wider operation is not limited to resurfacing NR4. It also covers road asset management, maintenance arrangements, road-safety measures, overloading control and institutional systems. For road users, the practical next test is therefore not another construction percentage but how the upgraded road is maintained and performs over time, particularly through Cambodia’s wet season.