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
School Street and Wilton Avenue, Lakeview

Service Notes:

Services:

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
Status: In Use

 

Profile:

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.

Following these improvements, Clark Junction remained largely the same for nearly three decades. It is believed that 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 -- similar to 17th Junction was considered in the 1970s but ultimately dropped due to community concerns about noise and aesthetics, resulting in a veto by the U.S. Environmental Protection Agency. As such, the layout of the junction remained largely the same. 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.

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 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" (i.e. not grade-separated) 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.

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.

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)
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.

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.

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)

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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)

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

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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)