The Pan Island Expressway is the oldest and longest of Singapore
's expressways. Currently, it is also Singapore's longest road. It extends along the length of the island, connecting Tuas in the west to Singapore Changi Airport
in the east. Its length is 42.8 kilometres (26.6 mi).
Construction of the PIE started in 1964 and took place in four phases. The first phase involved widening the stretch of Whitley Road from Mount Pleasant Flyover to Thomson Flyover, Jalan Toa Payoh, Jalan Kolam Ayer, and Paya Lebar Way, and replacing all the traffic light junctions on these roads with grade-separated interchanges. Those stretches were completed in 1969. Similarly, a second phase was constructed in 1969 and was completed in 1975 from Whitley Road (Mount Pleasant Flyover) all the way to Jalan Anak Bukit.
Subsequently (third phase), the section from Jalan Eunos to East Coast Parkway
, which involved the construction of a new road, started construction in 1976 and thus led to the proposed interchanges, Bedok North Road Interchange, Upper Changi Road East Interchange and the connecting T-interchange at East Coast Parkway. This was completed in 1980. The western end started construction in 1977 to parallel via Jurong Road. The fourth phase, the western end from Jalan Anak Bukit to Corporation Road was completed in 1981. The expressway was 35 kilometres (22 mi) long when completed.
Modification and extension of the western end of the expressway started in 1992 to connect it to the Kranji Expressway which was being built at the time. A new 8 kilometres (5.0 mi) section was built. It forked from the existing PIE at Hong Kah Flyover, intersecting the Kranji Expressway at Tengah Flyover and ending at the Tuas Flyover with the Ayer Rajah Expressway. The 2 kilometres (1.2 mi) section of the old PIE from Hong Kah Flyover to Corporation Road was downgraded to an arterial road and renamed Jurong West Avenue 2.
As the amount of traffic using the KJE and PIE to Jurong Industrial Estate increased, the Land Transport Authority upgraded the stretch of the PIE between Tengah Flyover and Tuas Road to a four-lane dual carriageway from a three-lane dual carriageway. The work started in March 2004 and ended in March 2006.