Temporary Slow Zones Lifted and Orange Line Trains Resume Normal Speeds

January 21, 2011
The Chicago Transit Authority today announced that with the completion of its short-term repairs to the Orange Line signal system, all slow zone restrictions along the rail line have been lifted. Trains are now operating at their normal speeds in both directions and are averaging travel times of approximately 25 minutes between Roosevelt and Midway.
“As a result of CTA personnel working diligently and collaboratively with the system manufacturer to test and implement the necessary short-term solution, Orange Line service is being restored to normal operation two-weeks ahead of schedule,” said CTA President Richard Rodriguez. “I would like to thank our customers for their patience over the last few months. While there was no immediate risk to employees or customers, it was necessary for us to address this potential defect and implement the temporary slow zones as a precautionary measure.”
While performing inspections last April, the CTA discovered a potential defect in a component of the Orange Line’s signal system. Under certain circumstances the defect could have potentially resulted in a rail operator not being properly alerted to a train ahead via their in-cab signal system. There have been no malfunctions with the signal system.
Although the chances of such an event actually occurring were extremely rare, the CTA implemented additional safeguards until the signaling fault was properly addressed, including restricting trains to operating no more than 35 mph.
Initially, 75,400 feet (or nearly 76%) of the Orange Line was affected by the precautionary slow zones. During the peak of the slow zones, the travel time between Roosevelt and Midway was approximately 28 minutes – an increase of roughly three minutes. In the following weeks, slow zones were lifted from 20,178 feet (or approximately 29%) of track after personnel conducted additional inspections that determined certain portions of track were not susceptible to the failure mode. 
Before trains could resume normal speeds along the affected portions of track, CTA personnel had to implement a short-term solution, which required adjustments to the signaling frequencies on some system components. 
Additional upgrades to the Orange Line signal system are currently underway as part of the agency’s long-term solution, which will require the replacement of the component parts, such as retrofitting printed circuit boards with an improved transformer to prevent saturation. All work associated with the Orange Line signal system is scheduled to be complete later this year with no impact to rail service while work continues.
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