A second phase is on the cards for the testing of electric vehicles when the initial trial ends this month, and it could involve a bigger fleet.
Sources said government agencies are in talks with the trial participants about such a move, but they have not finalised the details.
The Land Transport Authority (LTA), when contacted, would say only that further trials may involve car-sharing and commercial vehicle fleets.
The tests to gauge the viability of electric vehicles in Singapore started in June 2011 and now includes 89 electric cars and 61 charging stations.
In the second phase, several hundred to 1,000 electric vehicles could be taking part, said the sources familiar with the discussions. It is, however, unclear if it would be opened to the public.
The public was not involved in the first phase.
Only cars registered by companies, institutes of higher learning and government agencies were in the test-bed conducted by a multi-agency task force led by the Energy Market Authority and LTA.
These cars are exempt from certificate of entitlement (COE) premiums and other car taxes.
Data collected show that electric vehicles can perform in local conditions and travel a maximum of 115km on one full charge.
The average driving distance is 41km, compared with 55km by fuel-powered cars.
While observers note that electric cars tend to be cleaner and more energy-efficient than fuel-powered cars, they say there are two major obstacles to the electric car movement taking off.
The first is the high cost of an electric car, which they say is too expensive for ordinary consumers without subsidies.
For instance, a Nissan Leaf, one of four models in the test-bed, costs about $180,000 without any waivers.
The second obstacle is the absence of a larger network of charging spots here.
The LTA spokesman noted that electric cars have "significantly higher" upfront costs. Even with car taxes waived, the life-time cost of owning and driving the vehicle in Singapore would likely be higher than a conventional vehicle with full taxes, she said.
"Nevertheless, with improved battery technology and economies of scale, EVs (electric vehicles) could become cheaper over time."
Mr Thomas Jakob, managing director of Bosch Asia Pacific, which manages the trial's charging infrastructure, said opening the second phase to car-sharing makes sense as the initial higher cost of the vehicles will be spread over a bigger group.
Mr Jakob added that the Government needs to take a more proactive approach to support electric cars or it could probably take till 2025 before such vehicles become mass-market cars.
Mr Tom Lokenvitz, the founder of Clean Mobility Singapore and electric car-sharing scheme Smove, said there should be a "smarter structure" when it comes to such vehicles.
Noting that the $20,000 rebate from the carbon emissions-based vehicle scheme does not offset the higher cost of an electric car, he suggested lowering the vehicle taxes or COE premiums for these cars.
Mr Haider Rashid, region president of South Asia for power technology group ABB, wants the Electronic Road Pricing charges to be reduced for this type of car.
He said another major constraint is anxiety over the maximum distance the car can travel.
To overcome it, more charging infrastructure needs to be installed first, he said. But it is a "chicken and egg" situation because more cars need to be on the road to make such installations viable.
Agreeing, Mr Jakob said: "Somebody has to come in and be the catalyst and push that issue along. So far, whatever has been done is not significant enough. The Government can do more."