CAPACITY OF ROAD TRAFFIC WEAVING ZONES

CAPACITY OF ROAD TRAFFIC WEAVING ZONES

SUMMARY The purpose of this research was to evaluate the capacity of weaving areas in Indonesia. Data were collected from one site in Bandung and two sites in Jakarta. Parameters for analysis of the traffic streams were obtained from video-recordings of traffic at the three sites; geometric characteristics of the study sites were measured in the field. From the analysis, the results indicated the pcu-values of motorcycles in the weaving area to be higher than those obtained by other researchers whose field measurements were made at the approaches to junctions. Employing a nonparametric statistical technique, it was concluded that the differences in pcu-values of motorcycle in the four weaving-section manoeuvres (left outer, right-cross weaving, left-cross weaving, and right outer flows) were not significantly different at a 95% level of confidence. Theoretical models for the calculation of the weaving capacity were chosen and applied in the present research. It was found that the traffic volumes obtained from the field observations were approximately twice those indicated by calculation in formulas developed in the United Kingdom. It is believed that this occurred because the Indonesian field sites were much J.onaer ; as expressed in terms of the width/length ratio, than the condition for which the British practice formulas were developed. Under these circumstances, greater opportunities were available for drivers at the Indonesian study sites to select gaps in the traffic stream to perform the weaving manoeuvre, and to select the position at which a gap would be utilized from a longer segment of highway. Great differences were found upon comparing the speed and density characteristics of the Bandung site and the two Jakarta sites. However, the maximum flow values, normalized to represent a single 3.5-m lane, had very little difference between the three study sites. The vehicular speeds associated with the derived maximum flow condition, during the morning observations ranged from 18 km/h at the Bandung site to 28 and 46 km/h at the two Jakarta weaving sections. Comparison of the research results with those from the v.s. HiEhway_Capacity Manual technique for assessment of operational analysis of a motorway weaving section indicated that the two Jakarta sites were operating at Level of Sevice = F (unstable flow) at the time of the observations.

RINGKASAN Tujuan dari penelitian ini adalah untuk mengevaluasikan kapasitas dari daerah weaving di Indonesia. Data diperoleh dari pencatatan di satu lokasi di Bandung dan dua lokasi di Jakarta. Parameter-parameter untuk menganalisa arus lalu lintas diperoleh dari rekaman video pada tiga lokasi tersebut. Hasil-hasil menunjukan nilai satuan mobil penumpang ( smp) dari sepeda motor di daerah weaving lebih besar dari yang diperoleh dari peneliti-peneliti lainnya yang mengukur pada pwersimpangan. Dengan menggunakan teknik statistik non parametrik, disimpulkan bahwa perbedaan nilai smp dari sepeda motor pada empat arus didaerah weaving ( tepi kiri, menyilang kekanan, menyilang kekiri, dan tepi kanan) tidak ada perbedaan yang cukup berarti pada selang kepercayaan 95%. Model teoritis untuk perhitungan kapasitas weaving, dipilih dan digunakan pada penelitian ini. Nilai yang didapatkan dari penelitian di lapangan kira-kira dua kali hasil perhitungan berdasarkan rumus-rumus yang dikembangkan di Inggris. Hal ini mungkin terjadi karena panjang lokasi penelitian di Indonesia, seperti yang dinyatakan dalam perbandingan antara lebar dengan panjang, tidak tepat sama dengan kondisi di Inggris dimana rumusrumus tersebut dikembangkan. Dalam keadaan ini, pengemudi di Indonesia mempunyai kesempatan yang lebih besar untuk memilih celah (gap) diantara arus lalu lintas untuk melakukan gerakan menyilang (weaving) dan memilih posisi celah yang lebih lebar pada ruas jalan. Ditemukan adanya perbedaan yang cukup besar antara sifat-sifat lalu lintas a.l., kecepatan dan kepadatan pada ketiga lokasi survey. Meskipun demikian volume maximum satu jalur dengan lebar 3.5 m mempunyai perbedaan yang kecil diantara ketiga lokasi studi. Dari pengamatan pagi hari pada saat volume maximum diperoleh kecepatan kendaraan sekitar 18 km/jam, sedang di kedua lokasi di Jakarta diperoleh kecepatan sekitar 28 km/jam dan 46 km/jam. Dengan mengoperasikan kedua lokasi penelitian di Jakarta sebagai motorway dan kemudian membandingkan dengan metode Highwaz_Capacity_Manual, diperoleh hasil bahwa pada saat pengamatan, kedua lokasi tersebut beroperasi pada tingkat pelayanan F (arus tidak stabil). vii