Kurzwelle
Some routes numbered in the 900s are high frequency routes. High frequency bus services operate at minimum every 15 minutes between 7am and 7pm on weekdays, 8am and 7pm on Saturdays, and 9am and 7pm on Sundays. Since 2014, several high frequency routes have been introduced, and other routes have been renumbered to the 900s to indicate high frequency.