Signal Patterns for Improving Light Rail Operation
Wintana Miller, Associate Transportation EngineerWith Mark Madden, P.E., P.T.O.E.DKS Associates
Transportation in Tacoma Initial Pilot Project Update to Project Signal Timing
What’s 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
What’s Next?
Thank You