Overcrowding, long waits, and not enough trains are among a litany of complaints by GO train commuters after a scheduling change that came into effect last month.

Many of those problems are the "necessary result" of repairs and construction, made worse by the extreme heat conditions of the last few weeks, according to Metrolinx, the Ontario government agency responsible for GO Transit.

That has meant mounting frustration for many passengers at train platforms, including Janine DesRoches. She told CBC News she has repeatedly tried and failed to get on morning rush-hour trains on the Lakeshore West line because there's been simply no space.

"You can imagine how frustrating it is when you have be at work at a certain time and can't get on a train. You have no choice but to wait for the next train, 30 minutes later!" DesRoches said. "That is completely unacceptable."

<a href="https://twitter.com/GOtransit">@GOtransit</a> another <a href="https://twitter.com/hashtag/lakeshorewest?src=hash">#lakeshorewest</a> delay. Time to provide a discount for the duration of the service change. <a href="https://twitter.com/hashtag/gotrain?src=hash">#gotrain</a> <a href="https://t.co/sByR53mOBZ">pic.twitter.com/sByR53mOBZ</a> —@NanciAbbondanza

Metrolinx chief operating officer Gregy Percy acknowledged "the inadequate customer service over the last few weeks," in a statement Thursday.

'It has not met our standard,' Metrolinx says

"I agree it has not met our standard or the reasonable expectations of our customers," Percy said, adding that he is a daily rider on GO's Lakeshore West line and has witnessed riders' frustration and disappointment in recent weeks.

Metrolinx spokeswoman Anne Marie Aikins said service changes in advance of two platform closures for construction of a new train shed at Toronto's Union station are behind most of the issues. At the same time, some older trains are also running with 10 coaches instead of the usual 12 while their HVAC systems are upgraded, leaving those trains with about 300 fewer seats.

That work is the regular maintenance Metrolinx typically does in July because ridership drops when students are out of school for the summer. Work on the coaches is expected to be finished by the end of the month.

Melinda Shiers, who commutes to Union Station from Whitby every day, said she's seen schedule changes cause trouble before, and they're usually resolved within a few days — but not this time.

"I have never seen it this bad and I've been taking the GO Train for 24 years. I've not seen it this bad and this chaotic," she said, adding that overcrowding on train platforms has also been a problem.

Percy said he is committed to a full investigation following the schedule changes which he said were the most drastic that Metrolinx has needed to make at any one time in GO's history.

High heat will mean slower trains

He also added the agency has made already acted to determine which trips are most vulnerable to delays and has "developed a number of strategies including additional resources and staff" to mitigate the delays, which he said have especially affected Lakeshore trains.

But with temperatures expected to remain around the 30 C mark at least for the next week, it's not certain that those strategies will solve the service disruptions.

"We've got a slow order due to extreme heat today and likely next two days unfortunately," Aikins told CBC News on Thursday, saying the heat-related delays are a necessary safety measure due to "sun kinks," which are bends in steel rails that can occur in high heat.

DesRoches says she'd like to see more trains during rush hour to accommodate the number of people that rely on the service.

​"The GO Train isn't cheap and riders are paying a premium for fast reliable service. It is definitely not being delivered..." she said.

Ontario Transportation Minister Steven Del Duca said in an emailed statement that he is aware of the recent service delays, and added that it's important that Metrolinx communicates with passengers about expected travel delays.

'They don't want to hear excuses'

"Our commitment to every one of GO's over 265,000 daily customers is that we will continue working to keep our service efficient, reliable and a valued part of your daily commute," he said.

For Shiers, the communication isn't enough.

"When people are tired, they just want to get home ... I'm tired of the apology — just fix the issues, please."

Others are taking the delays in stride.