The annual College Scholastic Ability Test (CSAT) will take place at 1,216 venues nationwide today.
Tens of thousands of police officers, police vehicles and taxis will be on stand-by near test venues to help students arrive on time.
The government also plans to increase the number of subway trains and buses running in the morning.
Civil servants and employees of major companies in most cities will be allowed to report to work at 10 a.m., one hour later than usual, in order to relieve traffic congestion.
Banks and the stock markets also decided to delay their opening times by an hour, to 10 a.m.
All landings and takeoffs at airports will be put on hold and drivers must lower the speed of their vehicles near test sites during listening comprehension exams so as not to disturb the students.
Traffic will be banned from within 200 meters of test locations until the exam finishes at 5 p.m.
According to the Ministry of Education, more than 640,000 people applied for this year's exam, consisting of five sections — the Korean language, mathematics, English, social and natural sciences, and a second foreign language.
Scores from the test will determine whether students can enter their favored universities for the 2015 academic year starting in March. The ministry said test scores will be released to students in mid-December.
As on all previous test days, family members and friends of test-takers will gather around the test sites to cheer them on and wish them luck. Some parents may accompany their children to encourage and relax them, while others will be seen praying outside schools where their children are taking the exam.