the next phase of these works, the 6-lane stretch would be expanded from Tanjung Malim Interchange Exit 121 to Slim River Interchange Exit 126. Exit 117 Sungai Buaya Interchange An interchange at Sungai Buaya, Selangor, between Rawang and Bukit Beruntung Interchange was constructed between 2011 and 2013. This new interchange was opened to traffic on 10 January 2014. Exit 152 Alor Pongsu Interchange An interchange at Alor Pongsu, Perak, between Bandar Baharu and Bukit Merah Interchange was opened on 7 June 2016. Fourth lane addition In July 2010, the operator, PLUS Expressways, announced that the government had awarded contracts to build a fourth lane on a stretch from Rawang to Jalan Duta. The construction was completed in 2015. The Kilometre Zero of the entire expressway is located at the Malaysia-Thailand border. Bukit Kayu Hitam to Sungai Dua, Butterworth The expressway begins at the Bukit Kayu Hitam checkpoint in Kedah, where across the border in Thailand the road continues as Phetkasem Road. The expressway proceeds southwards concurrently along the old Federal Route 1, which has not been upgraded and is still a limited-access road. The first grade-separated interchange, which is with route 194, provides access to the northwestern state of Perlis. The route then enters the heart of the town of Changlun, where it intersects with a few local roads with traffic lights. South from the town are several rural villages with residential roads intersecting with the expressway. Just to the north of the town of Jitra, route 1 continues southwards while the expressway bends southeast to bypass the said town, marking the end of the concurrency and the start of the controlled-access highway proper. Just to the east of the town is the Jitra Toll Plaza, where a one-time payment is made. After the toll plaza the expressway continues southwest, entering the district of Kota Setar and interchanging with route 1 near Kepala Batas. Shortly south is the Hutan Kampung Toll Plaza, where ticket tolling begins. The expressway runs east of the city of Alor Setar, where it makes two interchanges with the Sultanah Bahiyah Highway (route 255), both leading to aforementioned city. Past the city, route 1 returns to run parallel to the expressway, both running southeasterly to enter the district of Pendang, where the expressway interchanges with a local route leading east to the town of the same name. Proceeding southeast, the expressway enters the Kuala Muda district.