Under what circumstances is a U-turn prohibited for motor vehicles?

[AidenLee]

The following situations prohibit U-turns: 1. When there are no left-turn or no U-turn signs; 2. Crossing solid lines to make a U-turn is prohibited; 3. When the central guardrail or green island is close to the stop line, U-turns are not allowed during a red light; 4. U-turns are prohibited on pedestrian crossings. When making a U-turn, the clutch must be engaged. Below is relevant information about the clutch: 1. Classification: Clutches are divided into four types - electromagnetic clutches, magnetic particle clutches, friction clutches, and hydraulic clutches. 2. Principle: The clutch consists of friction plates, spring plates, a pressure plate, and a power output shaft, located between the engine and the transmission. It transmits the torque stored on the engine flywheel to the transmission to ensure the vehicle delivers appropriate driving force and torque to the drive wheels under different driving conditions, falling under the powertrain category. During semi-engagement, the clutch allows a speed difference between the power input and output ends, meaning it transmits the appropriate amount of power through this speed difference.