Perpustakaan Digital ITB

Abstract : Lane width standards for Indonesian roads have been taken from the Indonesian Geometric Design Standards for Highways which are mostly based on experience in other countries with a longer history of motorisation. Unfortunately, there is little information which either supported or opposed the use of these measures in Indonesia and, at the same time, there are many major changes in vehicle characteristics. The study developed an estimation of optimum theoretical lane width based on the review of vehicles lateral placement distributions for different speeds and for two lane widths. The analysis was focused only on a traffic engineering view point. Surveys of the lateral placement were carried out on 1 site on the Jagorawi toll road, which has 3,75m wide lanes and 1 site on the Japek toll road, which has 3.60m wide lanes. Both were four-lane divided rural freeways radiating from the capital, Jakarta. These sites represented a range of nearly similar cross-section designs. Data collection was carried out using a video recording system in daylight. The passenger ears lateral placement distributions in the outer lane showed a normal distribution. The study also found that the main factors affecting lateral placement at the sites were lane width and speed. A variation in lane width from 3. 60m to 3.75m produced a variation in lateral placement of about 0.10m, where vehicles on 3.75m lanes travelled nearer to the right-hand lane line. Vehicles at speeds of less than 70kph travelled about 1.05m further from the right-hand lane line and vehicles at speeds more than 90kph travelled about 0,50m nearer to the right-hand lane line. Vehicles travelling at speeds between 70kph and 90kph travelled at an average distance of 0.30m from the right-hand lane line. The optimum theoretical lane width was found to be 3.70m. This measure was approximately similar to the measure of 12ft (3.66m) used in the USA. The study thus found that the lane width on the Jagorawi was too wide but on the Japek the lanes were probably slightly too narrow. The study recommends to review in depth the existing lane widths and introduce different lane widths for outer and inner lanes.