The TTC has cut down on the number of subway closures it will need this year, but parts of the system will still be out of service on most weekends in 2017.

The transit agency has scheduled 35 weekend closures between now and Dec. 3, according to a presentation that will go before the TTC board next Wednesday. That’s fewer than the 38 scheduled shutdowns in 2016.

More than half of the stoppages, or 20, will affect Line 1 (Yonge-University-Spadina), while portions of Line 2 (Bloor-Danforth) will be closed 10 times, Line 3 (Scarborough RT) four times, and Line 4 (Sheppard) just once.

A version of the presentation posted online Friday and reported by the Star misstated the number of closures for each line.

TTC spokesperson Stuart Green acknowledged that the closures frustrate customers, but he said they allow the transit agency to perform critical upgrades to the subway system. The TTC also performs work overnight, but shutting down the subway over a single weekend allows crews to do the equivalent of five weeks of overnight work, he said.

“It’s inconvenient for our customers, but it’s necessary work. We’re trying to modernize the system.”

Work the TTC completed during last year’s closures included replacing more than 5,000 metres of rail, installing 180,000 metres of signal cabling, and performing major maintenance on eight rail crossovers.

Most of the Line 1 closures this year are necessary for the TTC to implement the new automatic train control (ATC) signalling system, which will allow the agency to run more trains at higher speeds and with more reliable travel times. In those 13 cases, the line will be shut either from St. George to Downsview, or Wilson to Downsview.

The TTC plans to have ATC operational on portions of Line 1 by the time the subway extension to York opens at the end of the year.

Because of unrelated construction along the route of Line 1, the TTC won’t be running regular replacement shuttle bus service between Lawrence West and St. George stations during closures of the western arm of that line. Instead, Green said that east-west bus service will be doubled, to allow customers to access subway stations on Yonge for north-south trips.

According to the presentation, the TTC has found some ways to better manage closures, including “special operating procedures” that will allow it to close a smaller portion of Line 1.

Enacting parking restrictions during closures has drastically improved the reliability of shuttle buses, resulting in travel times that improved by as much as 47 per cent.

The TTC was criticized last year for shutting down the subway on weekends with major events, including one weekend in September when large portions of Line 1 were closed while thousands of people were trying to get downtown for the World Cup of Hockey and a pair of baseball games between the Toronto Blue Jays and the New York Yankees.

Green said the TTC tries to prevent these types of conflicts, but “some of those are going to be unavoidable.” The agency can’t foresee a sports team making the playoffs later in the year for instance, he argued, and it needs to order equipment and schedule workers well in advance.

“There’s a lot of pre-planning that needs to go into the closures and changing them at the last minute is not always an option.”

The first closure of 2017 is scheduled for Jan. 21 and 22, between Downsview and St. George stations on Line 1.

The remaining closures are listed below, along with the reason for them being shut down.

January 21/22 – Line 1: St George to Downsview - ATC

February 25/26 – Line 1: St George to Downsview - ATC

March 4/5 – Line 4: Full line – track and switch work

March 18/19 – Line 2: Kennedy to Warden – track and switch work

April 1/2 – Line 1: King to St Andrew – track work

April 8/9 – Line 1: St George to Downsview – ATC

April 14-16 – Line 2: St George to Broadview – City work on Prince Edward Viaduct and TTC maintenance

April 22/23 – Scarborough RT – life extension, track and infrastructure work

April 29/30 – Line 1: St George to Downsview – ATC

May 6/7 – Scarborough RT – life extension, track and infrastructure work

May 13/14 – Line 2: Broadview to St George – City work and TTC maintenance

May 20/21 – Line 1: St George to Downsview – ATC

May 27/28 - Line 2: Broadview to St George – City work and TTC maintenance

June 3/4 - Line 1: St George to Downsview – ATC

June 10/11 – Line 2: Broadview to St George – City work and TTC maintenance

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June 17/18 - Line 1: St George to Downsview – ATC

June 24/25 – Scarborough RT – life extension – track / infrastructure work

July 8/9 – Line 1: Bloor to Lawrence – rail grinding

July 15/16 – Line 1: Lawrence West to Downsview – track and switch work

July 29/30 – Line 1: St George to Downsview – ATC

Aug 12/13 – Line 1: St George to Downsview – ATC

Aug 19 – Scarborough RT– life extension, track and infrastructure work

Aug 20 – Line 2: Broadview to St George – structure maintenance

Aug 26/27 – Line 2: Islington to Kipling – track work

Sept 9/10 – Line 2: Islington to Kipling – track work

Sept 16/17 – Line 1: St George to Downsview – ATC

Sept 23/24 – Line 2: Jane to Ossington – rail grinding

Oct 7-9 – Line 2: Broadview to St George – City work and TTC maintenance

Oct 14/15 – Line 1: Davisville to Lawrence – track, switch work

Oct 21/22 – Line 1: Wilson to Downsview – ATC

Oct 28/29 - Line 1: Davisville to Lawrence – track, switch work

Nov 4/5 – Line 1: St George to Downsview – ATC

Nov 11/12 – Line 1: Davisville to Lawrence – track and switch work

Nov 25/26 – Line 1: Davisville to Lawrence – track and switch work