Metrolinx crews continue the ongoing projects to upgrade the train-signalling system and maintain tracks in the Union Station rail corridor.

Crews are:

• upgrading cables - between Bathurst and York Streets.

• Crews work from 8 p.m. Saturday, June 13 until 5 a.m. Sunday, June 14 and continuing overnight nightly until 5 a.m. Saturday, June 20.
• During the project, crews work on the access pad, retaining wall and caissons. They also contain cables.
• Expect noise from power tools (grinding, hammering and welding) and moving equipment.

• maintaining tracks - John Street.

• Crews work from 8 p.m. Saturday, June 13 until 5 a.m. Sunday, June 14 and continuing overnight nightly until 5 a.m. Saturday, June 20.
• They’re replacing a “rail ladder” (elevated track.)
• Expect noise.

• upgrading signals - south side of the tracks, Union Station to Scott Street.

• Crews work from 8 p.m. Friday, June 12 until 5 a.m. Saturday, June 13 and continuing overnight nightly until 5 a.m. Tuesday, June 16.
• The project includes capping caissons and installing impedence bonds in the Scott Street area.

• impedance bond work provides continuity between the track circuits for the direct current propulsion power and distributes the propulsion current between the two running rails.
• caisson cap work at CA5 for signal 852-858 is ongoing as crews prepare to install a new signal bridge near Scott Street. Crews are pouring concrete this week.

• Expect noise from drilling, hammering, high-mast daylighting and and back-up beepers, when trucks and other equipment reverse.

• installing impedence bond - south side of the tracks between Scott Street and the Don River.

• Crews work from 8 p.m. Tuesday, June 16 until 5 a.m. Wednesday, June 17.
• Expect noise from drilling, hammering, high-mast daylighting and back-up beepers, when trucks and other equipment reverse.

• installing impedence bond - north side of the tracks between Scott Street and Queen Street East.

• Crews work from 8 p.m. Monday, June 15 until 5 a.m. Tuesday, June 16 and continuing overnight nightly until 5 a.m. Friday, June 19.
• Expect noise from drilling, hammering, high-mast daylighting and back-up beepers, when trucks and other equipment reverse.

• replacing rail ties - Tracks 5 and 6 near Sherbourne Street

• Crews work from 8 p.m. Wednesday, June 17 until 4:30 a.m. Thursday, June 18 and from 8 p.m. Thursday until 4:30 a.m. Friday, June 19 to prepare the site.
• They then work from 8 p.m. Friday until 4:30 a.m. Saturday, June 20 and continuing overnight nightly until 4:30 a.m. Monday, June 22 to replace the ties.
• Crews must treat ties with creosote before they can install them. Expect odour.

• installing fencing - north side of the tracks between Parliament Street and Queen Street West.

• Crews work from 8 a.m. until 5 p.m. Monday, June 15.
• The fencing helps crews get ready for installing a retaining wall for signal bridge 951-955.

According to Merriam-Webster Dictionary, an impedance bond is “an iron-core coil of low resistance and relatively high reactance… to provide a continuous path around insulated joints… and to confine the alternating-current signaling energy to its own track circuit.”

Metrolinx says, “Impedance bond installation is a common approach used to achieve continuous traction current in a two rail system. Impedance bonds are essentially centre-tapped coils, which offer low impedance to traction current, while offering high impedance to signalling current.”

“High-mast daylighting” refers to illuminating a work site using a lighting tower during overnight work. Otherwise, “daylighting” means opening up — exposing to light — a previously underground or covered structure, such as a tunnel.