The proposed design speed for urban expressways as recommended by the Indian Roads Congress (IRC) is 80 km/h. This speed limit is established based on various factors such as safety, traffic flow, and the design of the roadway.

Factors influencing the proposed design speed of urban expressways:

1. Safety: The design speed of a roadway should be determined with the objective of ensuring the safety of road users. Higher speeds can increase the likelihood and severity of accidents, especially in urban areas with higher traffic volumes and frequent intersections. Therefore, a design speed of 80 km/h is considered appropriate to maintain safety on urban expressways.

2. Traffic flow: The design speed should be selected to provide an efficient flow of traffic. Higher speeds on urban expressways can lead to traffic congestion, reduced capacity, and increased travel times. A design speed of 80 km/h allows for a smooth and efficient movement of vehicles, minimizing delays and maximizing traffic throughput.

3. Roadway design: The design speed is also influenced by the physical characteristics of the roadway, including alignment, curvature, and sight distance. Urban expressways typically have more complex geometries compared to rural highways, with frequent interchanges, ramps, and intersections. A design speed of 80 km/h allows for appropriate curves, sight distances, and other design elements to accommodate the urban environment.

Importance of adhering to the recommended design speed:

1. Safety: Adhering to the recommended design speed helps ensure the safety of road users. It allows drivers to navigate the roadway comfortably, reducing the risk of accidents and collisions.

2. Traffic flow: Following the recommended design speed helps maintain a smooth and efficient flow of traffic. It minimizes the chances of congestion and delays, contributing to improved travel times and overall traffic operations.

3. Consistency: A consistent design speed across urban expressways ensures uniformity in roadway design and driver expectations. It helps drivers to anticipate and respond to roadway conditions more effectively.

In conclusion, the IRC recommends a design speed of 80 km/h for urban expressways. This speed limit is determined based on considerations of safety, traffic flow, and roadway design. Adhering to this recommended speed helps ensure the safety of road users, maintains efficient traffic flow, and provides consistency in roadway design.