Clark Junction is seen looking north on July 22, 2007, as a Kimball-bound Brown Line train passes through the interlocking and crosses over main line tracks 1 and 2 to access the Ravenswood branch. The 1976-built Clark Tower on the right was rehabilitated in 2006, with the interior renovated and a new tower panel installed; at the same time, the switches and signals at the junction were also replaced. For a larger view, click here. (Photo by Graham Garfield)

Clark Junction
School Street and Wilton Avenue, Lakeview

Service Notes:


Red Line: Howard

Purple Line: Evanston

Brown Line: Ravenswood

Quick Facts:

Address: 946 W. School Street (Clark Tower)
Established: May 18, 1907
Original Line: Northwestern Elevated Railroad
Rebuilt: 1976, 2005-06
(new switches and signals, rehabbed tower)
Status: In Use



Clark Street junction and station as they looked just prior to the 1913 switch to right-hand running. A Loop-bound Ravenswood train waits at the far left for southbound express and local trains to pass. For a larger view, click here. (Photo from the CTA Collection)

Clark Junction and its associated tower were placed in service on May 18, 1907 to connect the Ravenswood branch to the North Side Main Line. The junction is located near the corner of School Street and Wilton Avenue, just southwest of the corner of Clark and Roscoe.

The junction joins the two-track Ravenswood branch with the four-track North Side Main Line, whose two inside tracks are express tracks and whose outer tracks were local tracks. The branch's southbound track merged into the southbound local track, while the branch's northbound track diverged from the northbound express track. A series crossovers south of the junction, between School Street and Belmont station, allowed trains to then move back and forth between the express and local tracks as needed. Although the precise location and arrangement of the crossovers has changed over the years, the junction is still generally laid out in this manner.

Clark Tower was originally located at the north end of the junction, between the tracks of the main line and branch. A local station already existed at Clark Street just south of Roscoe when the junction was established immediately south of the station. The tower was placed at the south end of the southbound station platform, an ideal place to oversee the junction as well as the approach tracks in all three directions. The tower itself was a two-story affair with a wedge shaped plan and hipped roof. Its architecture was more practical than of any particular style, but did feature decorative window frames and sills, and belt course moldings. The interior space was tight. With windows on all sides for maximum visibility, the tower was heated only by a small iron potbelly stove in the corner of the room. The junction was equipped with a hand-operated lever form of switch and signal control. This made the interior a dizzying array of levers and switches, all of which had to be precisely aligned by a vigilant towerman.

The new Clark Tower is seen looking northwest in 1976. For a larger view, click here. (CTA photo)

Over the next several decades, Clark Junction remained relatively unchanged. Clark station closed in 1949, the victim of the closure of low-usage stations as part of the CTA's North-South Route service revision. While the station was demolished a few years later, the tower remained, as well as a small piece of the south end of Clark's southbound platform around the tower.

In the mid-1970s, the CTA undertook a project to modernize Clark Junction. The old semaphore signals were replaced with multi-aspect (colored light) wayside signals. A new, more spacious interlocking tower was also constructed. Situated on the east side of the main line tracks, the new tower was five stories high, stretching from street level to a control room cantilevered over the tracks. Access was provided to the metal-clad building from both street-level and track-level. The tower room on the top floor featured large picture windows on three sides for visibility and provided more room for the towerman to work. The new interlocking was controlled by an electric entrance-exit tower panel, which allowed routes to be established by means of merely pressing a few buttons as opposed to working that huge mechanical levers of the old tower. The tower was built at a cost of $249,000 as part of a CTA signaling program funded by the state and federal governments. The new interlocking plant at Clark Junction placed was in service on August 22, 1976. The new tower was completed a few months later. At that time, more than 950 trains carrying 130,000 people passed through Clark Junction each weekday.

Even with the improvements the new interlocking plant brought, Clark Junction remained a busy place whose "flat junction" layout (i.e. not grade-separated) necessitated conflicting moves. The most complex and time-consuming move through the junction involves northbound Ravenswood (now Brown Line) trains, which run on the outside (local) track [Track #4] along the four-track main line. To turn onto the Ravenswood branch at the junction, outbound Ravenswoods have to cross the northbound inner (express) used by North-South (now Red Line) trains. Once on the inner northbound track [Track #3], northbound Ravenswood trains take a diverging route at a turnout switch which requires them to cross the southbound inner track [Track #2] used by southbound North-South trains and the southbound inner track [Track #1] used by inbound Evanston (Purple Line) Express trains during the rush hour. This means that for a northbound Ravenswood train to make it onto the branch, north- and southbound North-South trains and southbound Evanston Express trains have to wait for the Ravenswood to make it across the at-grade junction, a sometimes time-consuming affair during rush periods when a high level of service is scheduled.

A northbound Brown Line train passes through Clark Junction, crossing tracks 1 and 2 at grade to get onto the Ravenswood branch, on a snowy February 7, 2004. The at-grade crossing, causing conflicting movements that limit through-put capacity, are why a grade-separated flyover has been proposed at various times. For a larger view, click here. (Photo by Graham Garfield)

A flying junction -- one in which the diverging tracks cross over or under the main line, so as not to block trains when crossing onto the branch -- conceptually similar to 17th Junction was considered as early as the 1950s, and received renewed interest beginning in the 1970s. More serious study of creating a flyover to grade-separate the junction was undertaken in the early 1980s as part of CTA's planning and engineering to realign two of the "L"'s through-routes and re-pair the Howard line with the Dan Ryan branch to create a realigned North-South Route (what is today called the Red Line). As part of creating the Howard-Dan Ryan service, each of whose high ridership were a better match than the branches' then-current pairings, CTA planned for a number of projects to increase capacity on the new through-route, including expansions of Howard and 98th yards and re-siting Addison station as an island platform instead of two side platforms to reduce switching delays. Another project CTA studied to reduce switching delays and increase capacity was creating a grade-separated junction at Clark to remove conflicting train movements. Ultimately, the CTA decided not to pursue the Clark Junction grade-separation project at that time and the Howard-Dan Ryan project proceeded without it. As such, the layout of the junction remained largely the same for nearly three decades.

On June 18, 1987, a new Addison Interlocking was placed in service north of Addison station. In addition to a local control panel, Clark Tower was modified to able to remotely control Addison Interlocking as well.

Clark Junction is one of the busiest flat junctions on the "L" after Tower 18. By the early 2000s, a short section of northbound track at Clark Junction saw up to 40 trains per hour during the evening peak -- 20 northbound Brown Line trains and 20 northbound Red Lines. To put this in proper context, there is a comparable short section at Aldgate North Junction, one of the busiest on the London Underground, that sees 30 trains an hour. in 2002, Clark Junction was the busiest CTA rail crossing on a 24-hour basis, serving 876 trains each weekday.


Brown Line Capacity Expansion Project

As part of the Brown Line Capacity Expansion Project, whose primary purpose was to renovate 16 Brown Line stations to accommodate 8-car trains and provide ADA-accessibility, the signal system on parts of the Brown Line were planned to be upgraded and modernized.

Clark Junction is seen looking southeast from the Ravenswood branch on April 18, 2003. The 1976-built Clark Tower is seen in the background. For a larger view, click here. (Photo by Graham Garfield)

On October 14, 2004, the Chicago Transit Board approved a $45.5 million construction contract for Aldridge -- Mass, AJV (A Joint Venture) to upgrade the signal system. Aldridge rehabilitated the Brown Line's signal system from Kimball to Western, which involves installing signal equipment along the tracks and rehabilitating Kimball Tower. At Clark Junction, Aldridge installed a new signal system from Armitage on the south to Addison (North Side Main Line) and Lakewood (Ravenswood branch) on the north. The work on this stretch, which became known as the "Clark Junction Corridor" or simply "the Corridor" during the project, included the installation of 14 new interlocked crossovers at five locations -- Belden, Altgeld, Barry, Clark Junction, and Lakewood-Seminary -- new signals, relay houses, and local control panels, and the rehabilitation of Clark Tower. Work in the Clark Junction Corridor began in late 2004.

During much of 2005 and 2006, single-track and reroute operations were required at night, on weekends, and during other off-peak periods as contractors Aldridge, Safetran, Target Electric, and Suarez worked to install the new crossovers and lay the necessary signal and communications lines. By 2006, most of the crossovers were installed at the locations outside of Clark Junction as contractors worked to completed the installation of relay houses and signals at those locations. These new interlockings required the installation of signal platforms, metal cantilevers on which wayside signals and associated equipment are mounted. The new Lakewood-Seminary Interlocking on the Ravenswood branch came on-line March 29, 2006. Effective May 15, 2006, the new Barry Interlocking was fully in service as well. On October 30, 2006, the new diamond crossovers between Tracks #1 and #2 at Belden and at Altgeld were placed in service. On November 13, 2006, the left-hand crossover between Tracks #3 and #4 at Altgeld and associated interlocking plant were placed in service.

During the winter of 2005-06, the contractors with the CTA Track Department began installing the new crossovers at Clark Junction. This work would take several months, as it involved a lot of complicated staging to replace the switches while maintaining rail traffic. Replacement of crossovers within the Clark Junction plant required the Red and Brown lines to undergo extensive reroutes and, for the latter, single tracks in the junction area to vacate the tracks where the new specialwork was being installed.

CTA Track Department personnel and contractors are working, with the help of a crane, to lift the new diamond crossover between tracks #3 and #4 into place on May 20, 2006. For a larger view, click here. (Photo by Graham Garfield)

As a result of the track modifications at Clark Junction, a temporary change was made in the operation of Brown Line shuttle trains effective April 10, 2006. Still berthing at Belmont on Track #1, rather than being routed to Track #3 then onto the northbound Ravenswood branch track at Clark Junction the trains operate against traffic northbound on Track #1 and onto the branch, then are switched onto the northbound track at Lakewood-Seminary Interlocking, essentially operating in a tower-protected single-track mode.

In April 2006, a new relay house was installed at Clark Junction immediately north of the tower. While the tower was being rehabilitated, control of Clark Junction was temporary transferred to a local panel in the relay house. Control of the junction was slowly cut over to the relay house over the course of the summer of 2006. Because each track was cut over one at a time, control of the junction was actually split between the tower and the relay house for approximately one month, requiring two towermen to establish train routings in the interlocking. As one could imagine, this required close coordination between the two towermen for the timely movement of trains. During this period, the towerman assigned to Clark Tower was in charge of all train movement through Clark Junction, with the towerman assigned to the relay house control panel not permitted to establish any lineups unless specifically authorized by the Clark Tower towerman.

The cutover began over the weekend of July 22-23 and completed over the weekend of August 26-27, 2006. Vacating of Clark Tower on August 27, the contractors began gutting the structure for its rehabilitation. Renovation included the installation of a new, larger tower panels that will allow remote control of all interlocked crossovers from Addison and Lakewood on the north to Armitage on the south. Contractors repainted the exterior of the tower building in September 2006 and work progressed throughout autumn on the installation of new infrastructure inside.

Effective September 29, 2006, the new, bi-directional interlocking at Clark Junction was fully placed in service. At that time, all cab and wayside signals were functional on all tracks within the Clark Junction interlocking limits.

Work at Clark Junction concluded in late 2006. In November 2006, control of Clark Junction was returned to the newly-rehabilitated Clark Tower. Final work on the tower and interlocking were completed during the rest of 2006 and early 2007. The new Clark Tower master panel has the ability to remotely control all of the interlockings in the Clark Junction Corridor -- Armitage, Belden, Altgeld, Barry, Clark, Addison, and Lakewood-Seminary interlockings. On January 4, 2007, Clark Tower assumed control of Brown Line shuttle trains making their turnback move through Lakewood-Seminary Interlocking. This move was somewhat short-lived, as on April 1, 2007 -- concurrent with the beginning of "Three-Track Operation" on the North Side Main Line -- the Brown Line shuttles began turning from south to north through Barry Interlocking, south of Belmont station rather than single-tracking back to Lakewood-Seminary. Clark Tower controls this move as well.

Funding for the contract was provided by the Federal Transit Administration -- both Full Funding Grant Agreement funds and formula funds -- the Regional Transportation Authority and the Illinois Department of Transportation.


RPM Red-Purple Bypass Project

As part of the Red and Purple Modernization Program (RPM), a multi-phase program to completely rebuild the northern sections of the Red and Purple lines and provide CTA with the ability to add trains to meet the demands of growing ridership, the CTA proposed to build a grade-separated junction at Clark Interlocking to reduce conflicts between trains and increase capacity through the junction.

Conceptual rendering of the junction with a flyover track, looking north from Belmont. For a larger view, click here. (Image courtesy of CTA)

Officially called the Red-Purple Bypass by CTA, and alternately referred to elsewhere as the Clark Junction Flyover or Belmont Flyover, the project was part of the RPM planning going back to 2009-10; as planning got more advanced, CTA began more explicitly promoting the flyover portion of the RPM program in 2014 to elicit public feedback and comment. Under the CTA's plan, northbound Brown Line trains would proceed along a dedicated rail line above the Red and Purple line tracks to get from track 4 on the North Side Main Line to the Ravenswood branch, eliminating the need for it to cross the other three tracks of the main line at-grade and stopping all Red and Purple line train movements through the junction to get onto the branch.

The total project cost is pegged at $570 million. The anticipated cost to construct and modernize the track and structure as part of the Red-Purple Bypass Project is estimated at $320 million. Additional work that would be performed as part of RPM Phase One would include bringing the Brown Line track structure west of the rail junction into a state of good repair and modernizing the signal system on the Red and Brown lines near Clark Junction. This work is included in the additional improvements expected to cost $250 million.

Conceptual rendering of proposed Red-Purple Bypass with and without redevelopment, at Clark Street and Buckingham Place, facing northwest. For a larger view, click here. (Image courtesy of CTA)

CTA argues that the improvement would allow them to significantly increase the number of trains run along the Red Line to reduce overcrowding and meet growing demand for transit service. Benefits of building the Red-Purple Bypass include being able to run up to 15 more trains per hour in one direction on the three lines during the afternoon rush and up to 12 more morning trains, cutting delays and overcrowding up and down the line. This would include the addition of up to eight more Red Line trains per hour during rush periods, which could accommodate up to 7,200 additional customers per hour during rush hour -- the equivalent to adding two traffic lanes on Lake Shore Drive in each direction. Currently, the most the agency can do is 40 to 44 trains per hour in one direction on the Red, Purple and Brown Line tracks. According to the Chicago Metropolitan Agency for Planning, 185,000 new residents are projected to move into Red and Brown Line service areas by 2040. To meet future demand, the service needs to be increase in this corridor to serve more riders during rush periods, but CTA says that with current infrastructure constraints the junction has already reached capacity.

The CTA evaluated several different alternatives to the flyover/bypass, including (with reasons CTA dismissed each option):

  • building a tunnel or subway to separate the junction (would have a substantially larger project footprint for construction, greater impacts on properties and the community, and longer construction duration and greater costs);
  • operating extra trains between Belmont and the Loop (would require an extra turn-back track to be built north of Belmont station, with nearly as many property acquisition impacts as the Bypass, and would still not address the capacity increases needed along the entire length of the Red Line);
  • having the Red Line tracks ramp over the northbound Brown Line track instead of vice versa (would not eliminate property impacts, and severe operational impacts during construction);
  • "stacking" the Purple Line tracks over the Red Line tracks to narrow the main line right-of-way requirement (would have a longer construction duration, result in greater property impacts, have substantial operational issues, and visual impact of double-stacked structure);
  • lengthening the platform at Belmont station to run 10-car trains to increase capacity (doesn't help if all other stations on the Red Line aren't also lengthened); and
  • making signal improvements instead to allow trains to run closer together (without removing the bottleneck at the junction, only minimal improvements are possible, estimated that at most, one additional train per hour could be added).

Conceptual rendering of proposed Bypass with and without redevelopment, facing northwest at Clark Street near Roscoe Street.. For a larger view, click here. (Image courtesy of CTA)

All other options studied either did not solve the core issue, or did not provide sufficient relief and additional capacity, according to the CTA.

Although the plan -- or more generally, it's goal of increasing capacity through the corridor to allow a great service frequency -- enjoys relatively broad support, many central Lakeview residents are opposed to the flyover, which at the time was projectd to require the demolition of 16 buildings. Opponents say the proposed flyover, which would be 40-45 feet tall at its highest point, would be an eyesore for the neighborhood. Some are concerned about the vacant property that will result from the property demolitions, pointing to buildings that were razed for the renovation and expansion of Belmont station in 2006 that, as of 2016, was still vacant (though, it should be noted, the point at which the station project was complete enough to allow sale and redevelopment of those parcels came in the middle of an economic and real estate downturn). Residents form the Coalition to Stop the Belmont Flyover to lead the opposition to the project, which included a November 2014 ballot referendum that involved the three precincts of the 44th Ward that would be most heavily impacted by the demolitions. Residents voted overwhelmingly against the project, with 72 percent of the 800-some people who voted opposing the measure.

FTA and CTA published an Environmental Assessment (EA) for the Red-Purple Bypass Project on May 19, 2015, established a 30-day public comment period to accept formal comments, and hosted a public hearing for the EA on June 3, 2015. Based on a review of the EA and all public comments received, FTA issued a Finding of No Significant Impact (FONSI) for the Red-Purple Bypass project in late 2015.

CTA began demolition of buildings adjacent to the flyover the week of March 4, 2018. The demolition begins more than a year before groundbreaking for the flyover structure itself is expected to occur.

The CTA is demolishing 14 buildings in the area for the project. CTA said they planned to knock down 10 buildings in March 2018, before opening day at Wrigley Field. Those include five buildings on the west side of Wilton Avenue, four on Clark Street, and one on Roscoe Street.

Demolition of four other buildings on Clark is scheduled for fall 2018.

In addition to the 14 buildings the CTA is contracting to have torn down, another property on Sheffield has been partially demolished by its owner. Two parcels acquired for the project are vacant lots, and another is a surface lot. The historic Vautravers building at 947-949 W. Newport Ave. will be relocated by the CTA, rather than demolished.

The CTA has spent $32 million on real estate acquisitions and relocation costs for the bypass, while demolition is expected to cost an additional $3 million. The CTA has acquired all the buildings it needs for the project, and they are all vacant.

A contract for construction on the flyover will be awarded at the end of 2018, and work to begin in 2019.1


ClarkJct00.jpg (266k)
The two Clark towers coexisted for a short time. This photo looking north from the new Clark Tower in 1976 shows the old Clark Tower at the split in the junction as a southbound Ravenswood All-Stop train of 6000s comes off the branch. Note the semaphore signals still present along the tracks. (CTA Photo)

cta2600s05.jpg (39k)
A North-South train of Budd/TA-built 2600s has just passed Clark Tower as it approaches Belmont station on its way to the South Side in July 1988. (Photo by James Raymond)

ClarkJct01.jpg (135k)
View looking south at Clark Junction on September 3, 2001. (Photo by Graham Garfield)

ClarkJct04.jpg (203k)
The renovated Clark Junction is seen looking south on January 4, 2007. Visible in this view are the rehabilitated Clark Tower, the Clark Relay House in front of it (which temporary controlled the interlocking while the tower was being rehabbed), the new diamond crossovers that provide flexibility at the junction, and new wayside home signals. (Photo by Graham Garfield)

ClarkJct07.jpg (267k)
The maze of switches that make up Clark Junction are seen looking north from Belmont station on March 20, 2015 as northbound Red and Purple line trains move through the interlocking. The tower is visible on the right, peaking out from the buildings that back up to the tracks. (Photo by Graham Garfield)



1. Wisniewski, Mary. "As the buildings come down, CTA's Belmont flyover closer to reality in Lakeview". Chicago Tribune. March 12, 2018.