Signal Patterns for Improving Light Rail Operation Wintana Miller, Associate Transportation Engineer With Mark Madden, P.E., P.T.O.E. DKS Associates
Transportation in Tacoma Initial Pilot Project Update to Project Signal Timing Whats Next Signal Patterns for Improving Light Rail Operation
Transportation in Tacoma
Downtown Tacoma
Tacoma Link Light Rail
Initial Pilot Project
Parties Involved Problems Found Methodology Challenges Initial Pilot Project
City of Tacoma Sound Transit Pierce Transit DKS Associates – Technical Advisers Parties Involved
Periodic Gridlock Train Headways: 10 minutes (600 seconds) Signal Cycle Length: 70 seconds Potential Solution: Coordinate Train and Signal Operation Problems Found
Main Objectives: Compatible cycles = repetitive operation Same time base = predictable action across systems Predictable train travel times Coordinating Train and Signal Operations
Picking a Compatible Cycle Length 100 second cycle Synchronized Clocks US Official Time: Atomic Clock in Colorado Springs Sound Transit Train Data Set Train Schedule Project Method
Time Space Diagram
External Logic Allowed for One Timing Plan Conservative dwell times Unable to use check out detectors No event plans or seasonal variations Remaining Challenges
City of Tacoma in the process of upgrading signal system New signal system has been selected Fine tuning LRT operations Signal System Upgrades?
Project Update
New Plan Needed New Light Rail Parameters New Traffic Signal Parameters Unique Phasing for Preempts New Signal Pattern Development
Driven by New Station Construction New Station in Place Before New Controllers Need for New Plans
Train Headways Train Travel Times Station Dwell Times New Light Rail Parameters
New Headway New Cycle Lengths 90 seconds New Pedestrian Timing (per 2009 MUTCD) Decreased walking speed from 4.0 ft/sec to 3.5 ft/sec New Traffic Signal Parameters
Unique Phasing for Preempts
Normally two phases Train preempt activate left turn phase Avoiding the left turn trap Commerce St Phasing
Support 120 second cycle length Shorter dwell times during off-peak hours Longer dwell times for special events Whats Next?
Thank You