NHK has developed an FM multiplex broadcasting system using a new digital modulation method called level controlled minimum shift keying (L-MSK) which is a kind of MSK. This system is multipath-proof, and has a transmission capacity of 16 kbps. Moreover, it has a compatibility with radio data system (RDS) because they use different frequency bands. Transmission tests were carried out to measure the performance of the 16 kbps L-MSK system in the service area of the NHK Tokyo FM station. These tests revealed that this system was superior to RDS in terms of the correct reception rates obtained in mobility. FM multiplex broadcasting using L-MSK has many merits for traffic information services.