TORONTO - Greater Toronto Area travellers could be riding electric GO trains to the airport by 2018 -- if the province hops aboard.

The agency behind the plan to electrify two rail corridors and a dedicated air-rail link says trips would be faster and trains would pull into stations five minutes apart in peak periods, similar to Toronto's subway service.

Critics charge that hundreds more trains would roll through residential neighbourhoods, and hundreds of millions of dollars in waste is built into the project.

The Metrolinx board of directors on Wednesday approved the $1.6-$1.8 billion plan to switch from diesel trains to electric on the Lakeshore and Georgetown corridors over the next 20 years.

Metrolinx president Bruce McCuaig said electric trains would save $18 million in annual operating costs. They would move faster and offer more frequent service, he said.

"Electrification is the start of getting the vision of having service as frequent as every five minutes in the peak period on our rail corridors."

The improvements could lure two million commuters to GO Transit's current daily 200,000 daily ridership, he estimated.

But hundreds of trains rumbling through neighbourhoods won't please residents, said New Democrat Cheri DiNovo.

Phase 1 -- a $457-million link between Toronto's Union Station and Pearson International Airport -- would be completed in seven to nine years, said McCuaig.

Transportation Minister Kathleen Wynne signalled the province is rolling forward, but only with the environmental assessment on the air-rail link for now, which she called the first step towards electrifying the line.

"It would not be responsible for me to commit to you a large dollar figure at this point when we won't be able to necessarily provide that," said Wynne.

Wynne said there's not enough time to electrify the air-rail link before the 2015 Pan Am Games. Diesel trains that will be converted later to electric will be used instead.

"Balderdash," said DiNovo, who added about $400 million will be wasted by not making the route electric from the start.

Hybrid buses could be used during the Games instead of buying diesel trains, she said.

Clean Train Coalition spokesman Keith Brooks said about 100 people protested outside the Metrolinx meeting, demanding it ditch its plans for diesel trains on the air-rail link.

Metrolinx is building infrastructure that can accommodate electric service to minimize waste of taxpayers money, said McCuaig.

The link could cut 1.2 million car trips off the road in its first year, the ministry estimated.