What do the numbers 261, 145, and 520 mean in Subject 1?

[VanRafael]

This is a numerical memorization method. 1. 261: When visibility on the highway is less than 200 meters, the speed must not exceed 60 km/h, and the distance between vehicles should be no less than 100 meters. 2. 145: Correspondingly, when visibility on the highway is less than 100 meters, the speed must not exceed 40 km/h, and the distance between vehicles should be no less than 50 meters. 3. 520: And when visibility is less than 50 meters, the speed must not exceed 20 km/h, and the driver should exit the highway from the nearest exit as soon as possible. Below are the requirements for Subject 1: For first-time applicants of a motor vehicle driver's license or those applying to add a permitted vehicle type, after passing the Subject 1 test, the vehicle management office should issue a driving skills examination permit within one day. The driving skills examination permit is valid for three years, and the applicant must complete the Subject 2 and Subject 3 tests within this validity period. If the tests are not completed within the validity period, the passed test subjects will be invalidated.