Kelajuan aliran bebas bermaksud kelajuan di mana pemandu dapat memandu dengan bebas kendereaan mereka tanpa sebarang halangan. Untuk bahagian asas lebuh raya ekspress, had kelajuan yang di benarkan adalah dalam sekitar 90 km/j hingga 110 km/j. Tujuan utama kajian ini dijalankan adalah untuk mengenal pasti kelajuan aliran bebas kenderaan yang menggunakan lebuh raya express. Tiga kaedah digunakan untuk mengenal pasti kelajuan aliran bebas kenderaan yang mengguna Lebuhraya UtaraSelatan PLUS di beberapa lokasi yang rata-ratanya terletak di negeri Perak dan Pulau Pinang. Kaedah yang pertama ialah berdasarkan U.S. HCM 2000 (Trasportaion
Research Board, 2000), kaedah kedua ialah menggunakan kaedah hasil kajian Bang (1996) untuk Indonesian Highway Capacity Manual dan kaedah ketiga ialah dengan menggunakan kaedah konvensional hubungan kelajuan-aliran-ketumpatan berasakan model daripada Model Greenshield, Model Underwood dan Model Drake. Kajian dimulakan dengan merekod video lalu lintas menggunakan kamera litar tertutup (CCTV) di beberapa tapak kajian. Kemudian diteruskan dengan mengekstrak data melalui perisian TRIAS™ 3.1 SRM di mana data-data penting seperti aliran trafik, komposisi kenderaan, kelajuan dan kemajuan kenderaan. Hasil daripada kajian menggunakan beberapa kaedah akan memberi nilai kelajuan aliran bebas dan data-data lain seperti nilai kapasiti maksimum Qmax dan pekali penentu, R2 dimana akan membantu dalam mencari kaedah yang paling sesuai untuk mendapatkan kelajuan aliran bebas di bahagian asas lebuh raya ekspress.
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Free-flow speed is the speed where the vehicle can free to maneuver on the road without any obstacle beyond them. For the basic segment expressway, the speed limit would be about 90 km/hr to 110 km/hr. The main reason why these studies conducted is to find the free-flow speed of the vehicle travel on the basic segment expressway. Three methods are being used to find out the free-flow speed on several locations mainly located at PLUS North-South Expressway at Perak and Penang State. Method 1 based on U.S. HCM 2000 (Transportation Research Board, 2000), Method 2 is based on the study conducted by Bang et al. (1996) for the Indonesian Highway Capacity Manual and, Method 3 is based on the conventional speed-flow-density relationship established by Greenshield’s Model, Underwood’s Model and Drake’s Model. The studies started with the field work that requires video recording using the CCTVs at the site. The study continue with the data extraction from the video using the TRIAS™ 3.1 SRM software where vital data such as traffic flow, vehicle composition, speed and headway. The result of the studies shows that every method will provide different value of the free-flow speed as well as other data such as value of maximum capacity, Qmax and coefficient of determination, R2 which will help to determine the best method to determine free-flow speed at the basic segment expressway.
Analysis of free-flow speed at basic segment_Rosydi Sabri Bin Burhanud-Din_A9_2011_NI