What does it mean to have the letter K in front of the license plate number of buses in some cities, such as Jinan?

Every place is different. The earliest K prefix in Jinan means air-conditioned car, 2 yuan, not air-conditioned car line 1 yuan, but now many lines without K prefix are also air-conditioned cars mixed. As for the branch lines of K 10 and K 10, many stations on these two lines are the same.