Crosstown Glossary


'Mud slab' sounds like a flavour of ice cream, and 'Portal' is something out of the latest sci-fi drama. What do these mean in relation to construction for the Eglinton Crosstown? We often mention many terms that may be confusing if you are not involved with the project. To help, we have put together a glossary of terms that are often used when talking about the Eglinton Crosstown.


  • Stands for Automatic Train Control. A remote controlled system in which train operations are controlled entirely by software from a centralized control room. Crosstown LRVs will operate with ATC. 

Design Excellence

  • A set of principles laid out by Metrolinx to guide transit design in a way that goes beyond basic functionality. Design excellence principles cover engineering standards, aesthetics, and much more. Read about Design Excellence here.


  • The process of removing groundwater from an excavated pit. Without dewatering systems in place, groundwater can overwhelm a construction site and halt work. Read more here.

Duct Bank

  • A group of conduits designed to protect electrical cabling, often consolidated in a buried or encased structure. On the Crosstown, duct banks will run through the tunnels – read about them here


  • Stands for Eglinton Maintenance and Storage Facility. It is the large facility currently under construction on the former Kodak Lands north of Eglinton between Black Creek Drive and Weston Road. The EMSF will house the Crosstown’s LRVs every night, where they will undergo inspection, cleaning and maintenance.


  • The collective effort to install all systems in the Crosstown Tunnels required to operate transit service. The tunnel fit-out is currently ongoing.


  • Molds into which concrete can be poured. Formwork can be either permanent or temporary depending on the job, and can be made from a variety of materials such as plastic, timber or metal. 


  • Refers to depth/height relative to ground level. The underground section of the Crosstown is ‘below-grade’, the surface section is ‘at-grade’, and the elevated guideway is ‘above-grade’.

Integrated Art

  • Art built into the structure of a station as opposed to art mounted/displayed in the station. As part of its push for Design Excellence, Metrolinx commissioned eight pieces of art from Canadian and international artists. Read more about integrated art here.

Interchange Station

  • A station where transit riders can transfer between different TTC subway, bus, and SRT lines. The Crosstown will have three interchange stations: Cedarvale, Eglinton and Kennedy (which doubles as an intermodal station).

Intermodal Station

  • A station where transit riders can transfer to a different mode of public transit, such as GO or the UP Express. Intermodal Stations include: Mount Dennis, Caledonia and Kennedy (which doubles as an interchange station). 


  • Invert refers to the base level of concrete that will comprise the floor section of a structure. Originates from the ‘invert level’, a civil engineering term for the floor level of a pipe, trench or tunnel. 


  • A drilling or mining ‘jumbo’ is a machine used to break through rocks in a mine. The Crosstown project uses a number of jumbos at its mined sites – Laird, Oakwood and Avenue Stations. 


Mud Slab

  • A layer of concrete that sits directly on top of soft/wet soil, but below the first structural concrete slab. 

Overhead Catenary

  • The system installed overtop the rails of a light rail system, to provide operational power to the LRVs. This system is used on light rail vehicles in place of a powered third rail, and is similar to the power lines for streetcars or trolley buses. 


  • Stands for Paid Duty Officer. PDOs are officers from the Toronto Police Services, and are used on the Crosstown to direct traffic and pedestrians around construction zones.


  • Vertical supports driven or poured into the ground, that together act as the frame for an excavated pit and later, the foundation for the station box. Piles can be steel, concrete or a combination of both depending on ground conditions and the load they need to bear. 


  • A point at which a train transitions from below-ground to the surface; entrances and exits from the tunnels. There are five planned portals on the Crosstown alignment: one at Black Creek Drive, one at Brentcliffe Road, two on either side of Don Mills Road, and one at Kennedy Station. 


  • Stands for Personal Protective Equipment. On Crosstown sites, proper PPE includes steel-toed boots, a hardhat, a reflective safety vest, safety glasses, and gloves. Proper PPE is essential for ensuring worker safety on job sites.


  • Refers to sections of building material (usually concrete) that are poured and set off-site, then brought on. This process helps to save time and space by minimizing labour performed on site. An example would be the precast sections of concrete that make up the walls of the Crosstown Tunnels.


  • Short for reinforcing bar, usually made in the form of a steel grid. Concrete is poured around rebar to create a reinforced concrete that has increased tensile strength.  


  • A right-of-way is a dedication of land use for transportation purposes. Right-of-ways cover many uses, including highways, railways and bike paths. Many sections of the Crosstown involve working within urban roads, a type of right-of-way owned by the City of Toronto.

Roof Slab

  • A concrete slab that forms the roof of an excavated pit. The thick concrete slab is capable of supporting a large amount of weight, allowing traffic to continue above while excavation and construction continues below. Learn more about roof slabs here.


  • Refers to the setup of construction zones in a specific area. Staging changes are often required as work advances in order to relocate work zones. Because work for many stations is required over entire intersections, construction is performed in different ‘stages’ so that sections of each intersection can remain open for traffic and pedestrians. 

Station Box

  • An underground structure, often box-like or rectangular in shape, which contains many components of a transit station including the station platforms, concourse, mechanical systems, etc.

Structural Steel

  • Steel that will be part of a final station structure. This excludes rebar in concrete and steel used in piles. The first structural steel for the Crosstown was installed in March 2017 at the EMSF, and the first station structural steel installation took place in December 2017 at Mount Dennis Station.


  • Stands for Tunnel Boring Machine. A large and complex machine used to dig through the earth and create tunnels underground without disturbing the surface. The Crosstown TBMs created tunnels 5.75 metres wide, and advanced at a rate of 10 metres a day. Learn more about the TBMs here


  • Stands for Toronto Hydro-Electric System Limited. THESL systems include all electrical lines and street lamps in the city, which must often be relocated to make way for Crosstown construction.


  • A device that strengthens support-of-excavation. Tiebacks are drilled through the sides of piles into the ground at an angle, and function like a screw into a wall, providing greater load capacity to the pile.

Traffic Flip

  • The change-over from one construction ‘stage’ (setup) in an intersection to the next. Often, multiple traffic flips are required over the course of years to construct different sections of a transit station.


  • An all-encompassing term for any sort of connection moving a service from a provider to a consumer through public space. 

Dry Utilities: All utilities that don’t move water, such as electrical and internet cables. 

Wet Utilities: All utilities that move water, such as sewage pipes and watermains. 


  • An underground pipe or conduit used to move water. Watermains are frequently rerouted/relocated to clear the way for underground construction.