Greater Colombo Urban Transport Development Project

The Outer Circular Highway (OCH) to the City of Colombo is a new circular expressway and runs approximately 15 km from the City Centre.

This expressway connects several trunk roads and expressways, radially extends from Colombo City and has successfully eased heavy traffic in the Colombo Metropolitan Region since its completion.

The total length (20.0km) comprises main bridges and viaducts (8.0 km), ramps and frontage road bridges (2.0km) and overpass bridges (0.8 km). The 3.25km long viaduct was the longest in Sri Lanka upon completion.

A curved PC box girder was applied to one of the interchange ramp bridges, the first of its kind in Sri Lanka, while crash cushions, protect drivers from collisions with bridge ramp noses at viaduct interchanges.

Provision for two future additional lanes from the present four-lane configuration were incorporated into the projects, including across its five interchanges with toll plazas.

The expressway is built with heightened resilience to disasters as the expressway passes through a low land area prone to regular flooding, in order to not encroach on hilly areas promoted for housing development.

The design considered a stochastic high flood level with a 50-year return period. Soon after the completion, the expressway experienced a significantly major flood. A local highway below the expressway became inundated and impassable. However, the main carriageway of the expressway was higher than the flood level and sufficiently secured traffic between the north and south of the Colombo Metropolitan Region.