site.btaFlyover on Tsarigradsko Shose at Fourth Kilometre Junction Opens 50 Years Ago

On March 22, 1976, the flyover on Tsarigradsko Shose (then Lenin Boulevard) at the Fourth Kilometre junction over G. M. Dimitrov Boulevard was officially opened in Sofia. The reinforced concrete structure is 500 metres long and 30 metres wide, with three traffic lanes in each direction. The elevated roadway rises above a roundabout, with service roads and pedestrian underpasses built to accommodate traffic to and from the Dianabad and Mladost boroughs.

The purpose of the structure was to ensure uninterrupted traffic flow along the Sofia–Plovdiv route. Until then, the intersection at Tsarigradsko Shose had been controlled by traffic lights and was one of the busiest in the capital.

The project was completed in less than three years and opened ahead of schedule on the eve of the 11th Congress of the Bulgarian Communist Party, which began in late March 1976.

The construction of the flyover was part of the broader modernization of Sofia’s road infrastructure during the 1970s.

Ahead of the opening of the flyover half a century ago, the BTA Home News Desk bulletin reported:

Intense Construction Activity on Lenin Boulevard Flyover

Sofia, March 11, 1976 /BTA/ In just a few days, traffic along the capital’s Lenin Boulevard will be fully normalized, and Sofia will have its main entry and exit thoroughfare completed. The builders have kept their promise and significantly shortened the construction timeline for the flyover of the boulevard.

(…) Construction was carried out using a system of segmental lifting slabs with a specialized installation—a Bulgarian patent. The 22 elements forming the bridges were cast on the ground, pre-stressed, then lifted into place, joined with reinforcement and concrete, and only then were the 24 supporting columns cast.

The flyover is now fully complete. It consists of two bridges, each 13.7 metres wide. Together they provide six traffic lanes (three in each direction), two sidewalks 1.5 metres wide, and a central divider. The surface is asphalt concrete. Beneath the structure, an asphalted roundabout has been formed, which, together with additional lanes, ensures smooth, conflict-free traffic at this complex junction. (…)

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New Facilities in the Capital

Sofia, March 22, 1976 /BTA/ This morning, the first buses crossed the flyover on Lenin Boulevard. Traffic has been opened on the largest engineering structure in the capital, a result of 30 months of intensive work by the Inzhstroy construction team.

The nearly 500-metre-long flyover has two carriageways, each 13 metres wide, allowing uninterrupted movement of three traffic streams in each direction. The structure is unique, built using a Bulgarian invention by engineer Lalo Raykov, chief designer of the bridge and chief engineer of Inzhstroy, together with engineer Nesho Topalov, General Director of Inzhstroy, and Marcho Minev from the Higher Institute of Civil Engineering [present day University of Architecture, Civil Engineering and Geodesy].

What is new in this bridge construction method is that reinforced concrete elements are cast on site, pre-stressed, and then mounted onto separately cast columns. This makes it possible to create highly efficient and economical bridge structures without joints, ensuring long exploitation life without the need for ongoing maintenance and repairs. It also allows for a significant reduction in construction time. After the foundations were laid, all remaining work was completed in a record 12 months, enabling the builders to report today that the project was finished nine months ahead of schedule in honour of the 11th Party congress.

The boulevard regained its historical name, Tsarigradsko Shose, in 1990, after previously being named Lenin Boulevard.