Transit Path-Building: “To Multipath or Not to Multipath” David Kurth & Suzanne Childress (Parsons) Erik Sabina & Sreekanth Ande (DRCOG) Lee Cryer (Denver RTD) May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

Issues with Path-Building / Mode Choice “The FTA advised us to do it…” Consistency Coherent Story “…and it’s a good idea.” Integrated Regional Model Concerns – DRCOG Detailed, activity-based model – needs consistency FasTracks, New Starts – RTD Logical transit paths Credible mode choice May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

} } The Crux of the Issue “Simple” Path-Builders & Mode Choice All-or-nothing Shortest path “Transit riders don’t behave that way” led to… “Complex” Path-Builders & Mode Choice Multi-path Optimal strategies Path-finder Multinomial Logit } } Nested Logit May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

Example RTD Path Options 3 Reasonable Paths Path 1: 2 Local Buses Path 2: 2 Local Buses Path 3: Local Bus, Rail, Mall Shuttle, Local Bus Travel Behavior Inventory (TBI) observations for all three! May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

OK, so what’s the issue? May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

OK, So what’s the issue? May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

OK, So what’s the issue? May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

Decisions, Decisions Complex Path-Builder / Simple Mode Choice Transit multi-path reliance Simple Path-Builder / Complex Mode Choice Transit multi-path avoidance Complex Path-Builder / Complex Mode Choice Just Say “NO!” May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

Transit Network Testing Opportunities TBI Data – Access and egress mode Individual routes used Individual choice regarding path options RTD System Reasonable options for paths Reasonable options for modes May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

Normal Transit Network Testing Route specific travel times Modeled versus observed Selected transit paths Heuristic (“That makes sense…”) Boardings per linked trip Assignment of observed on-board survey trips Comparison to observed boardings By route By service type By access mode (walk versus drive) May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

TBI Path-Matching Experiments Reviewed selected individual reported paths Some logical paths not selected Some multiple path options Some poor reporting by respondents Comparison to simple path-builder Total boardings / total linked trips By network combination (local only, premium only…) Prediction success tables Boardings per individual linked trip May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

Transit Networks for Path-Building Local Bus Only Local & Premium Bus Premium Bus Only Local Bus & Rail Rail Only Premium Bus & Rail All Modes 4 Times-of-Day: AM Peak PM Peak Off-Peak Early/Late 2 Access Modes: Walk Access Drive Access 56 Sets of Paths May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

Aggregate Path-Matching Experiments Walk Access – All Times-of-Day TBI Reporting Problems – Mall Shuttle May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

Example Local-Rail Paths – The Good TBI Reported Local Bus to Rail – Correct Path Found Rail Transfer Station Local Bus May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

Example Local-Rail Paths – The Bad TBI – Local Bus to Rail Only Bus Path Found Logical Bus-Rail Path Exists Local Bus Rail Option Here Transfer Station May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

Example Local-Rail Paths – The Ugly TBI – Local Bus to Rail Multi-path found: Bus Only Bus to Rail (to Mall Shuttle) Local Bus Path 1 Local Bus to Rail May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

Path-Building Experiments Path weights to encourage mode use Bus-rail paths reviewed Base case: Rail time = 0.7 x actual time FTA OK’d for existing DRCOG model Optional case: Rail time = 0.6 x actual time Pushing the FTA approval envelope May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

Path-Building Experiment Results Local/Rail Paths Base case 33/62 (53 percent) used rail Boardings/trip should be > 2.0 Optional case 43/61 (70 percent) used rail Boardings/trip “reasonable” Base selected due to “previous acceptability” May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

How Good is the Simple Path-Builder Approach? Prediction success tests Built paths for observed interchanges Based on observed mode combination Local only, premium only, rail only… Compared: Modeled to observed boardings Interchange-by-interchange May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

Prediction Success Results PM Work Trip – Walk to Rail Only May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

Prediction Success Results – Simple Path Builder 67 percent “correct” Unaffected by access mode IT WOULD REALLY BE NEAT TO REPEAT THIS ANALYSIS WITH “SMART” PATH-BUILDER!!!! May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

Prediction Success Results – Simple vs. Multi-path Builder AM Walk Access Trips Complex Approach Observed trips compared to “All modes” paths Simple Approach Observed trips compared to same network paths Local only, premium only… May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

Some Practical Issues Model Estimation Constraints May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

Recap Transit users Transit multi-path builders Pick individual paths Do not necessarily pick the same paths Do not necessarily pick logical paths Do not necessarily accurately report paths Transit multi-path builders Deterministic heuristic representing discrete choice Do not capture choice behavior May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

Conclusions Transit paths Are choice behavior Should be represented in mode / path choice Require substantial resources to model and estimate Common network validation measures that may not be sufficient Ability to assign all observed trips Matching observed boardings / linked trip May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15

…and Some Questions For Simple Path-Builder / Complex Mode Choice Approach Are there limits for path weights to “encourage” path options? Do path-building weights need to match mode choice relationships? Will inconsistencies impact user benefits? May 9, 2007 11th TRB National Transportation Planning Applications Conference -- Session 15