What is the reason for slippery conditions in tunnels during Subject 4?
4 Answers
The reason vehicles tend to skid inside tunnels is due to slippery road surfaces. Since tunnels are not exposed to sunlight, they remain relatively dark, and combined with water dripping from the mountain walls, the ground becomes slippery. The Subject 4 exam consists of 50 questions, presented in the form of case studies, images, animations, etc., with a total score of 100 points, and a passing score of 90. Subject 4, also known as the Subject 4 theory test or driver's theory test, is part of the motor vehicle driver's license assessment. After the implementation of the Ministry of Public Security's Order No. 123, the Subject 3 test was divided into two parts: the road test and an additional safety and civics knowledge test, commonly referred to as "Subject 4," which evaluates "driving ethics." Because this test is conducted after Subject 3, it is colloquially called the Subject 4 exam. Officially, however, there is no "Subject 4." Failing Subject 4 does not require retaking previously passed subjects (Subject 1, Subject 2, Subject 3). Candidates can schedule a retake on their own, and no additional fees are required for the retake. There are no restrictions on the number of retakes, but the validity period of the driving skills test permit is three years. If the applicant does not complete the exam within this period, the results of any passed subjects will be invalidated.
In the subject four exam, it's mentioned that tunnels are prone to slipping, mainly because tunnels have high humidity and poor ventilation, with water or dew often accumulating on the ground, making tires more likely to skid when driving over. Additionally, many vehicles tend to brake hard upon entering tunnels, and frequent braking leaves behind rubber marks and oil stains, which accumulate over time and reduce friction on the road surface. In winter, if the temperature difference is large, there's even more moisture, making the road even slipperier. If you take sharp turns or drive at high speeds in such conditions, accidents are bound to happen. Therefore, it's essential to slow down in advance, maintain a safe distance, turn on your lights, and drive cautiously—safety first. I think this is an experience that requires practicing several times during driving lessons to truly understand.
Tunnels are prone to slippery conditions primarily because they are enclosed environments with high humidity, where water accumulates on the ground and evaporates slowly. Additionally, frequent vehicle traffic and the friction marks left by tires during braking can make the road surface smoother, reducing traction. The fourth subject of the driving test emphasizes the need for extra caution when driving in tunnels due to the high incidence of accidents in such areas. Drivers are advised to reduce speed, avoid using high beams, maintain a safe distance, and refrain from sudden maneuvers. I've also noticed warning signs at some tunnel entrances reminding drivers that the road surface may be slippery, especially during the rainy season or cold weather. It's crucial to take necessary safety measures and not be complacent.
Why are tunnels so slippery? Mainly because the air inside doesn't circulate well, causing moisture to accumulate on the ground. Plus, with so many vehicles braking daily, the residue builds up, making the road surface smooth and slick. When entering, it's important to slow down and avoid sharp turns. This is even highlighted in the driving test (Subject 4) as a key reminder for safe driving, aiming to prevent skidding accidents.
