As of Saturday, new GO Transit fares kick in across the system.

Longer trips will cost slightly more, while trips under 10 kilometres will be significantly cheaper, slicing off about a dollar per ride for Presto card users.

But there's one group of customers who won't be in on the savings: commuters who prefer to use the UP Express train to make daily trips from Weston or Bloor GO stations to Union.

As GO Transit fares go down, the cost of a trip on the UP will remain the same — $4.71 to ride from Bloor to Union with a Presto card, or $5.02 to travel from Weston.

But commuter Gabriel Lawrence says the effect of Saturday's changes will hit him harder than that.

"Essentially, when they lowered GO Transit fares for short distances, they actually increased UP Express fares," Lawrence told CBC Toronto.

That's because riders like Lawrence, who takes the UP Express from Bloor to Union most days, will no longer be able to access GO-associated perks like the GO Transit monthly loyalty discounts or the $1.50 discount that comes with transferring from GO to the TTC.

Lawrence calculated what he believes the changes will cost the average commuter taking 42 rides a month, and says they could increase costs by about $30 per month, or about $90 per month for people who transfer to the subway.

A tale of 2 fare systems

In 2016, fare prices for GO Transit and UP Express rides were brought in line in an attempt to draw more riders to the UP, which, a year after it opened as Toronto's rail connection between Union Station and Pearson International Airport, was still running 90 per cent empty.

Both sets of riders began paying the same price and both were encouraged by Metrolinx to tap their Presto cards on GO-branded Presto machines — regardless of what kind of train they were riding.

That's when Lawrence started riding the UP in earnest.

"It was more [money] than a Metropass, but it was so much nicer. Compared to going on the subway to work, it's just a joy to take the UP Express."

The UP Express and GO Presto card readers sit across from each other at the Union Station UP Express platform. Prior to April 20, customers only riding as far as Bloor or Weston on the UP are encouraged to tap on the GO card reader machine. (Kate McGillivray/CBC)

Metrolinx spokesperson Matt Llewellyn acknowledged that the UP Express has become "extremely popular" with commuters heading downtown, noting that it has the highest customer satisfaction rate of any Metrolinx service.

"Part of this change reflects the different purpose of the UP Express service, which is actually about getting customers to and from the airport as quickly and efficiently as possible. As part of that, we're offering our commuting customers an even more affordable way to get downtown, which is by using our GO Transit Kitchener line," he said.

Watch where you tap

Come Saturday, the two fare systems will be re-segregated, and customers are being asked to use the Presto machine at the station which corresponds with the kind of train they're riding: silver for UP Express, and green for GO Transit.

"If you're going to get on an UP vehicle at either Bloor or Weston station, you tap an UP Presto device. If you're getting on a GO vehicle, then you will tap onto a GO device," said Llewellyn.

Llewellyn pointed out that customers who typically take the UP Express from Bloor or Weston are well placed make the switch to GO trains and take advantage of the new, reduced fare.

"I wouldn't say we've done anything to discourage customers [from using UP], it's the exact same price as it was before," said Llewellyn. "We've just offered customers who head downtown, in particular during the morning and afternoon rush hours, an even more affordable way to do that."

The UP Express runs every 15 minutes. A one-way trip between Union Station and Pearson Airport takes 25 minutes. (Kate McGillivray/CBC)

As for Lawrence, he says he prefers the UP's regular 15-minute service and worries that on the GO Kitchener line, he'll wind up waiting for trains.

Lawrence also says he's concerned by what he sees as an attempt to quietly introduce a significant change in the cost paid by UP commuters.

"I absolutely think that they were trying to quickly push it through," he said.