Perpustakaan Digital ITB

For safe execution of overtaking manoeuvres, which would reduce the congestion on a road, time gaps in the oncoming vehicle flow should be greater than the time traveled in the opposing lane by an overtaking driver. Incorrect judgement of gap creates a risk of collision. This varies from one driver to another, depending on the skill and experience of the driver, especially on two-lane two-way roads. This study of overtaking manoeuvres was conducted on two-lane, two-way rural roads. The data was collected by two cameras placed at the rear and the front of a test vehicle, and observations were made at four different test vehicle speeds i.e 30 km/h, 40 km/h, 50 km/h and 60 km/h. Data were obtained on the initial manoeuvre distance and time, distance gap and tracking-gap time at start of overtaking, time and distance traveled in opposing lane, distance gap and tracking-gap time at end of overtaking, accepted time/distance gap to on-coming vehicle and safety margin. The measurements were grouped on the basis of test vehicle speeds and the mean, 85 percentile, 15 percentile values were calculated. The data analysis indicates that : 1) time and distance of initial manoeuvre increased with increase in speed of overtaken vehicle. 2) intial acceleration decreased with increase in speed of overtaken vehicle. 3) time and distance traveled in the opposing lane increased with increase in speed of overtaken vehicle. 4) distance and time gaps to on-coming vehicle accepted by overtaking vehicle increased with increase in speed of overtaken vehicle. 5) the analysis of the relationship between overtaken vehicle speed and safety margin, tracking-gap time and distance gap at end of overtaking were inconclusive. The average of observed distance traveled in the opposing lane is generally not significantly different, at the 5 percent level, than the value recommended by Bina Marga, except for speed group 40 km/h, while the average of observed time spent in the opposing lane is greater than the value recommended by Bina Marga, except for speed group 30 km/h.