Chaloem Maha Nakhon Expressway

The Chaloem Maha Nakhon Expressway (ทางพิเศษเฉลิมมหานคร), also known as the First Stage Expressway System (ระบบทางด่วนขั้นที่ 1), is an expressway in Thailand, located in Bangkok. It is the first expressway to be opened in the country and is 27.1 kilometres in length. The expressway has played an important role in alleviating ground-level road traffic in Bangkok. The expressway is a controlled-access toll road. Rama IX Bridge, is part of the Tha Ruea–Dao Khanong expressway section.

History
Due to a significant increase in road traffic in the Bangkok Metropolitan Region, an expressway system was proposed in order to alleviate the heavy ground-level road traffic and in preparation for the predicted increase in car usage. The Expressway Authority of Thailand (EXAT) was tasked to construct Thailand's first expressway in 1978 to connect three main highways leading out of Bangkok to the outlying provinces. This was Vibhavadi Rangsit Road to the north, Debaratna Road to the east and Rama II Road (Thonburi - Pak Tho Road) to the south. A total of 8.51 billion baht was invested in the project, with mainly government funding and some funding from Japan International Cooperation Agency (JICA).

The first section between Din Daeng–Tha Ruea was completed and unofficially opened on 29 October 1981. It was officially opened on 4 January 1982. Its northern end terminated at Vibhavadi Rangsit Road in Din Daeng district and its southern end terminated at Tha Ruea (Port) Junction near Bangkok Port in Khlong Toei district. The second section between Tha Ruea–Bang Na was opened on 17 January 1983 and connected Tha Ruea Junction to Debaratna Road in Bang Na district. The third section between Tha Ruea–Dao Khanong was opened on 5 December 1987 and connected Tha Ruea Junction to Rama II Road in Chom Thong district.

Due to increased road traffic on the expressway, Rama IX Bridge was expanded in 2020 and is expected to be completed in 2023.

According to an official EXAT annual report, the expressway was used by 104,765,797 cars in the 2022 fiscal year, with an average of 302,791 cars per day.

Route
Kilometre 0 is counted at Din Daeng Interchange.