The development of Changi East, where the airport's Terminal 5 (T5) is being planned, will require major roadworks - including the possible construction of two parallel roads with a total of up to 20 lanes - to support expected higher traffic volumes.
Under preliminary plans, both roads will run side by side for about three quarters of a kilometre, before one breaks off and turns into the future T5, The Straits Times has learnt.
The other will lead to Changi Coast Road, which will be diverted from its current location as it separates the existing airport from the T5 site.
The plan is for motorists to be able to access the new roads from the Pan-Island Expressway, the East Coast Parkway and Xilin Avenue.
All three, which now have three lanes in each direction, will be expanded. Airport Boulevard will also become wider.
A source said: "Improving the traffic flow in the area will involve works on several major expressways and roads. To link the roads and expressways and for motorists to access the roads conveniently will require an extensive network of slip roads, entrances and exits - perhaps the most complex we have seen in Singapore."
A spokesman for the Land Transport Authority (LTA) said that the road development plans for Changi East have not been firmed up.
It will work closely with other relevant agencies "to plan the necessary infrastructure improvements to support and meet the transport needs of the airport expansion as well as the Changi East area", he said.
T5 is slated to open in the middle of the next decade with an initial capacity to handle up to 50 million passengers - more than T1 and T2 put together.
The development of Changi East, which aims to cement Singapore's position as a major airport for destination and connecting traffic, will also include the construction of aircraft maintenance and repair facilities, offices and hotels.
All this will require massive improvements, not just to the road network but public transport systems as well, experts said.
Nanyang Technological University adjunct associate professor Gopinath Menon said: "You must be able to get people to and from the airport quickly and seamlessly. We don't want travellers coming in from the air and then being stuck in jams on our roads."
The authorities have to be mindful not to confine widening and expansion works to just stretches near the airport, said National University of Singapore transport researcher Lee Der Horng.
He said: "It is important for the traffic capacity and flow to gradually build up and thin out so we avoid bottlenecks upstream and downstream."
Beefing up public transport services will be critical too, he said.
Plans have been announced for a new ground transportation centre to serve the future T5 and Changi East, with at least one, if not two, new MRT lines.
With the number of passengers set to increase in the coming decades and competition from rival airports becoming more intense, it may be time to consider an express rail service to Changi Airport, with city check-in and other related facilities, said Dr Lee.
"In Hong Kong, the express train takes you from the airport to city with just three stops in between. Once you reach the city, there is a comprehensive bus network to ferry travellers to all the main hotels in the area," he said.
Prof Menon said viability studies would first need to be done.
"At other airports in London for example, taxis are costly, so the main mode of transport for people travelling to and from the airport is the train. For us, taxis are less expensive and preferred not just by travellers with bags but visitors as well," he said.
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