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What is the Principle of Vehicle Speed Measurement?

2 Answers
JesseLynn
07/29/25 1:17pm
Vehicle speed measurement principle: The average speed measurement system operates through an automatic license plate recognition system. Two adjacent monitoring points are set up on the same road section to record the time a vehicle passes through them. The system then calculates the vehicle's average speed in that section and determines whether it exceeds the speed limit based on the preset standard. To safely pass through an average speed measurement zone: When you see an "Average Speed Measurement" sign by the roadside, reduce your speed to the specified limit and maintain it within the allowed range. If you exceed the speed limit at the starting point, you should try to adjust your average speed to the specified limit during the measurement section. As long as the calculated average speed upon reaching the endpoint doesn't exceed the limit, you won't be penalized for speeding.
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GraceRose
08/14/25 3:24am
I always worry about getting caught speeding when driving. The working principle of speed detectors is quite interesting. The common radar speed detection on roads emits radio waves that bounce back when hitting a vehicle, and the speed is calculated based on the change in wave frequency, similar to how bats use echolocation. Laser speed detection is more precise, like the speed guns used by traffic police, which emit infrared light and calculate the time difference of the light's round trip to determine the speed. However, these devices are greatly affected by weather and may malfunction on rainy or foggy days. Once when I was on the highway, I saw coils embedded in the road, which belong to inductive speed detection. When a vehicle passes over the coils, it causes electromagnetic changes. The distance between two coils is fixed, and the speed is determined by measuring the time difference it takes to pass. Nowadays, there is also video speed detection, which calculates speed by analyzing the displacement distance of a vehicle through continuous photos, though its effectiveness is poorer at night.
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Will an A2 Driver's License Be Downgraded After 12 Demerit Points?

According to previous regulations, a driver's license would be downgraded if it accumulated 12 demerit points. However, with the implementation of new regulations on April 1, 2022, holders of an A2 driver's license who accumulate 12 demerit points within a scoring cycle will no longer face downgrade. Instead, they need to participate in the study and examination of Subject 1 to clear the violation points and retrieve their driver's license. The A2 driver's license permits the operation of tractor-trailers, which can tow heavy and medium-sized full trailers/semi-trailers. Here, it's necessary to explain what a trailer is. Trailers are divided into two types: full trailers and semi-trailers. A full trailer bears its total weight entirely by itself, while a semi-trailer shares part of its total weight with the towing vehicle. Only drivers holding an A2 license can operate such tractor-trailers; even those with an A1 license are not permitted to drive them. To downgrade an A2 driver's license, one must visit the local vehicle management office with their ID card and driver's license: 1. An A2 license downgrade will result in a B1 or B2 license. The A2 license corresponds to tractor-trailers, the B1 license to medium-sized buses, and the B2 license to large trucks. Other vehicle types that an A2 license holder can drive include: B1 (medium-sized buses), B2 (large trucks), C1 (small cars), C2 (small automatic transmission cars), C3 (low-speed trucks), C4 (three-wheeled cars), and M (wheeled self-propelled machinery). Article 68 of the new traffic regulations stipulates: If a driver holding a license for large buses, tractor-trailers, city buses, medium-sized buses, or large trucks meets any of the following conditions, the vehicle management office shall revoke their highest permitted driving qualification and notify the driver to complete the downgrade and license exchange within 30 days: Being involved in a traffic accident resulting in death and bearing equal or greater responsibility, without constituting a crime. Accumulating 12 demerit points within a scoring cycle. Failing to undergo inspection for three consecutive scoring cycles. A driver's license, officially known as a motor vehicle driver's license or simply 'license,' is a document required by law for individuals to operate motor vehicles. Driving a motor vehicle requires certain skills. Without these skills, operating a vehicle recklessly could lead to traffic accidents. Generally, individuals cannot drive without a license. However, for those who have mastered safe driving techniques, the document allowing them to drive on roads is the 'driver's license,' which serves as a 'permit.' The permission to drive is granted through the issuance of a driver's license. This indicates that obtaining a driver's license is a formal process that must be conducted by a specialized authority. Internationally, a driver's license is defined as 'a document issued by the competent authority permitting the holder to drive a car.' In China, a driver's license is defined as: A motor vehicle driver's license is a legal certificate issued by the management department to individuals who, after learning and mastering traffic regulations and driving skills, pass the required examinations, permitting them to drive specific types of motor vehicles.
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What are the differences between the Audi RS4 and S4?

The differences between the Audi S4 and RS4 are as follows: 1. Different positioning: The Audi S4 is a performance model; the Audi RS4 is a high-performance model. 2. Different models and sizes: (1) The Audi S4 is a sedan with dimensions of 4770*1847*1404 mm, a wheelbase of 2825 mm, and a trunk capacity of 480L; (2) The Audi RS4 is a station wagon with dimensions of 4782*1866*1437 mm, a wheelbase of 2826 mm, and a trunk capacity of 505L. 3. Different power: (1) The Audi S4 is equipped with a 3.0T V6 turbocharged engine, producing a maximum horsepower of 354 hp and a peak torque of 500 Nm, with an official 0-100 km/h acceleration time of 4.7 seconds; (2) The Audi RS4 is equipped with a 2.9T V6 twin-turbocharged engine, producing a maximum horsepower of 450 hp and a peak torque of 600 Nm, with an official 0-100 km/h acceleration time of 4.1 seconds. 4. Different engine technologies: (1) The Audi RS4 features a high-speed engine first used in Audi's mass-produced models, with a maximum engine speed of 8,250 rpm. 90% of the engine torque can be continuously output within the speed range of 2,250 to 7,600 rpm, allowing the model to provide sufficient traction over a wider range. Additionally, with the FSI technology, the Audi RS4 can more effectively mix fuel and air, delivering even more powerful performance. (2) On the other hand, the Audi S4's low-pressure turbocharged engine excels in explosive power. Although its horsepower output is relatively conservative, it performs exceptionally well in low-speed torque. In some domestic acceleration competitions, an Audi S4 with a stage 1 tune can compete head-to-head with an Audi RS4.
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Which country does the Chevrolet car brand belong to?

Chevrolet is an American car brand, currently owned by General Motors in the United States. More information about Chevrolet is as follows: 1. Chevrolet was founded on November 3, 1911, by William C. Durant and Louis Chevrolet. 2. Chevrolet is also known as Chevy. It was acquired by General Motors in 1918 and is now the most international and popular brand under General Motors. Chevrolet is the best-selling brand of General Motors worldwide. 3. It offers a variety of models, including sedans, SUVs, recreational vehicles, sports cars, and pickup trucks.
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Why Can't New Energy Vehicles Be Charged?

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Can Fuel Additive Still Be Used After One Year of Expiration?

Fuel additive can still be used after one year of expiration, but its effectiveness will be significantly reduced. If the fuel additive has not been expired for too long, it can be used normally. However, if it has been expired for an extended period, such as half a year or two years, it will no longer be effective in cleaning carbon deposits. Below are the detailed explanations: Introduction to Fuel Additive: It is a common name for the third generation of gasoline detergent (also known as gasoline detergent or fuel additive). It is designed to address the carbon deposit issues in the fuel system of fuel-injected vehicles, quickly restore the engine to its optimal working condition, and compensate for certain deficiencies in gasoline properties while imparting new beneficial characteristics: such as improving atomization, reducing wear, protecting the engine, and lowering emissions.
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Why does the engine sound loud but the car doesn't accelerate when pressing the accelerator?

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