Pengaruh Kelelahan Pengemudi terhadap Frekuensi Kecelakaan Lalu Lintas: studi kasus Pengemudi Bus di Jalan Tol Jakarta - Cikampek = the influence of driver's fatigue factor to the frequency of ttraffic accidents: case study the bus driver on the Jakarta - Cikampek Toll Road - Lanny H. Tjakranata, author (1997)