Which type of roundabout is noted for giving the best performance according to traffic engineering standards?

• A. Multi-entry lanes with one circulating lane
• B. Single-entry lane and two circulating lanes
• C. Two-entry lanes with one circulating lane
• D. Single-entry lane with one circulating lane

Answer: (B)

The choice indicating that a single-entry lane with two circulating lanes provides the best performance aligns with traffic engineering principles focused on capacity and efficiency. In this configuration, the additional circulating lane increases the throughput capacity of the roundabout, enabling it to handle a larger volume of traffic entering and circulating compared to configurations with fewer circulating lanes.

This setup allows for better management of traffic flow, particularly during peak hours or in areas with high traffic demand, as it reduces congestion on entering and circulating approaches. It provides more options for drivers to maneuver and facilitates more efficient use of the available road space, decreasing the potential for delays and increasing overall safety by minimizing conflict points.

The other configurations, while functional, do not offer the same level of efficiency. Options with fewer circulating lanes may struggle to manage heavy traffic volumes effectively, potentially leading to backups and increased travel times. Thus, the design of the roundabout, particularly in terms of the number of circulating lanes, is critical in achieving optimal performance and safety in traffic flow.