The capacity of an uncontrolled intersection refers to the maximum number of vehicles that can pass through the intersection in a given time period. It is an important factor in traffic engineering and helps determine the efficiency and effectiveness of intersection design.

- Capacity Range:
The correct answer is option 'C', which states that the capacity of an uncontrolled intersection is 1200 to 1400 vehicles per hour. This means that under normal conditions, the intersection can handle a flow of vehicles within this range.

- Factors Affecting Capacity:
Several factors influence the capacity of an uncontrolled intersection, including:
1. Traffic Volume: The total number of vehicles approaching the intersection affects its capacity. Higher traffic volumes generally result in reduced capacity.
2. Traffic Composition: The mix of different vehicle types, such as cars, trucks, and motorcycles, can impact the capacity of the intersection. Larger vehicles may require more time and space to navigate the intersection, reducing the overall capacity.
3. Intersection Control: Uncontrolled intersections do not have traffic signals or stop signs. The absence of control devices may lead to more cautious driving behavior, potentially reducing the capacity compared to controlled intersections.
4. Geometric Design: The layout and design of the intersection, including the number of lanes, lane widths, and turning radii, can affect the capacity. Well-designed intersections provide sufficient space for vehicles to maneuver, reducing congestion and increasing capacity.

- Calculation of Capacity:
The capacity of an uncontrolled intersection is typically determined using empirical methods or traffic simulation models. These methods consider various factors, including the number of lanes, traffic flow characteristics, and the presence of pedestrian movements. By analyzing the traffic patterns and characteristics at the intersection, engineers can estimate the maximum capacity.

- Importance of Capacity Analysis:
Accurate capacity estimation is crucial in traffic engineering to ensure safe and efficient movement of vehicles. It helps in identifying potential bottlenecks and congestion points, enabling engineers to design appropriate mitigation measures. Capacity analysis also assists in determining the need for traffic control devices, such as traffic signals or roundabouts, to improve intersection performance.

In conclusion, the capacity of an uncontrolled intersection is in the range of 1200 to 1400 vehicles per hour. This capacity is influenced by factors such as traffic volume, traffic composition, intersection control, and geometric design. Accurate capacity estimation is essential for effective intersection design and traffic management.