ROUNDABOUT OR INTERCHANGE?

By: Yoana Suhartana

Traffic congestion is a major problem in large cities, particularly at complex intersections where multiple traffic streams converge. This issue arises due to the limited capacity of intersections, conflicting vehicle movements, and suboptimal traffic management. Efforts such as the installation of traffic lights, road widening, and traffic engineering have been implemented, yet these often provide only temporary relief. For instance, despite the installation of signalized control, the Hotel Indonesia (HI) Roundabout continues to experience congestion as traffic volume exceeds its capacity. A similar situation occurred at the Semanggi Interchange before the grade-separated system was constructed, where severe congestion persisted during peak hours despite traffic control measures (Haryanto, 2019).

One potential solution is the roundabout. A roundabout is a circular intersection where vehicles move counterclockwise (in the Indonesian context) with priority given to those already circulating within the roundabout. This system creates more organized flows, reduces vehicle speeds, and minimizes conflicts. According to the Transportation Research Board (2010), roundabouts can reduce fatal crashes and are more energy-efficient since vehicles are not required to make complete stops as they do at signalized intersections.

However, roundabouts are only effective under certain conditions. They are best suited for intersections with moderate to high traffic volumes, a limited number of approaches (typically three to five), and sufficient land availability. If traffic demand is too high or if the number of approaches is excessive, long queues may form at the entry points. Furthermore, roundabouts may cause confusion for drivers unfamiliar with the system and could create safety issues for pedestrians and cyclists if crossing facilities are inadequate (Silalahi, 2021). The HI Roundabout illustrates the suitability of this system for urban intersections with mixed but relatively slower-moving traffic. It connects Jl. MH Thamrin, Jl. Imam Bonjol, and Jl. Sudirman while also functioning as an iconic urban landmark. From spatial and aesthetic perspectives, the HI Roundabout was designed not only as an intersection but also as a symbolic city feature since the 1962 Asian Games, highlighting its historical and cultural significance (Setiawan & Pradoto, 2020).

An alternative solution for intersections with extremely high traffic volumes is the interchange. An interchange is a grade-separated intersection that eliminates traffic conflicts by using overpasses or underpasses, allowing continuous vehicle movement. This configuration significantly increases capacity and raises average travel speeds. The Federal Highway Administration (2010) notes that interchanges can improve traffic flow by more than 50% compared to signalized intersections. A successful implementation of this solution can be seen at the Semanggi Interchange, which has alleviated heavy congestion in Jakarta’s primary arterial network since its development.

Nevertheless, interchanges require stricter preconditions. They are feasible only at intersections with very high volumes, critical connectivity between arterial roads, and sufficient land and financial resources. Construction costs are substantially higher than those of roundabouts due to the need for bridges or tunnels, and the prolonged construction period often disrupts traffic flow temporarily. Environmental impacts are also greater, ranging from land-use changes to increased emissions. The Semanggi Interchange case highlights technical, spatial, and strategic factors behind its implementation. Technically, traffic volume in the area was extremely high, as it is the convergence point of major arterials (Jl. Gatot Subroto, Jl. Jenderal Sudirman, Jl. S. Parman, and toll road access). A roundabout would have created excessive conflict points, leading to bottlenecks. From a spatial standpoint, the area had long been designated as a primary junction with sufficient land for grade-separated construction. Strategically, the interchange connects Jakarta’s central business district, toll road access, and intercity corridors, making additional capacity indispensable (Haryanto, 2019; Fauzan, 2022).

In conclusion, the choice of intersection treatment must be tailored to the specific conditions of each location. The HI Roundabout demonstrates that roundabouts are effective in urban intersections with mixed traffic at lower speeds, while also serving symbolic and aesthetic functions as a landmark. Conversely, the Semanggi Interchange illustrates that grade separation is more suitable for intersections with extremely high traffic volumes, regional connectivity, and the need for uninterrupted flow. Thus, the decision between roundabouts and interchanges cannot be generalized but should instead consider traffic volume and patterns, the role of the road network, spatial availability, and socio-economic as well as aesthetic aspects of the city.

References:

Fauzan, M. (2022). Studi Efektivitas Interchange dalam Mengatasi Kemacetan di Simpang Semanggi. Prosiding Seminar Nasional Transportasi, 5(1), 211–220.

Federal Highway Administration (FHWA). (2010). Interchange Design Manual. U.S. Department of Transportation.

Haryanto, T. (2019). Analisis Kinerja Simpang Susun Semanggi Jakarta. Jurnal Transportasi, 19(2), 85–94.

Setiawan, R., & Pradoto, W. (2020). Kawasan Bundaran HI Sebagai Simbol Perkembangan Kota Jakarta. Jurnal Tata Kota, 12(1), 33–45.

Silalahi, B. (2021). Evaluasi Penerapan Bundaran pada Simpang Perkotaan. Jurnal Rekayasa Transportasi, 15(3), 102–110.

Transport Research Board (TRB). (2010). Roundabouts: An Informational Guide, Second Edition. National Research Council, Washington, D.C.