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