Kate Lyman, Portland State UniversityKate Lyman, Portland State University

Travel Time Reliability in Regional Transportation PlanningTravel Time Reliability in Regional Transportation PlanningAbstractTravel time reliability is an important measure of congestion and can serve as baseline for prioritizing improvements into a region’s transportation system. This paper begins with a literature review of travel time reliability and its value as a congestion measure. It then presents the methodology and results of a content analysis of twenty regional transportation plans from across the nation. This analysis concludes that travel time reliability is not currently used as a congestion measure, and that the most common measures of congestion were the volume-to-capacity ratio, vehicle hours of delay, and average speed. The paper then uses data from Portland, Oregon to provide a case study for how to prioritize roadways according to travel time reliability measures. The study concludes by providing recommendations to MPOs for ways to incorporate travel time reliability measures into regional transportation planning.

RecommendationsMPOs can incorporate travel time reliability into their RTPs

in the following ways:

1. State the improvement and maintenance of travel time reliability as a systemwide goal.

2. Evaluate existing transportation system using measures of travel time reliability.

3. Use results of the analysis to prioritize improvements into the transportation system that will improve reliability.

Objectives1. Analyze regional transportation plans for usage of travel

time reliability2. Analyze freeway segments in Portland, Oregon to

provide a case study of how to incorporate travel time reliability into regional transportation planning

3. Provide recommendations to MPOs on how to utilize travel time reliability

AcknowledgementsDr. Jennifer Dill and Dr. Robert Bertini provided invaluable support and input into this research. Dr. Kristin Tufte was instrumental in gaining the necessary data from the PORTAL data archive.

Daily PM Peak (4-6 PM) AM Peak (7-9 AM) Rating

I-5 NORTH 2004 22% 68% 33%

Average

2005 22% 68% 36%

2006 26% 68% 45%

2007 24% 63% 42%

Average 24% 67% 39%

I-5 SOUTH 2004 26% 68% 46%

Average

2005 21% 60% 34%

2006 22% 75% 34%

2007 22% 64% 37%

Average 23% 67% 38%

I-205 NORTH 2004 15% 60% 17%

Good

2005 17% 58% 28%

2006 19% 65% 36%

2007 19% 57% 40%

Average 17% 60% 30%

I-205 SOUTH 2004 17% 66% 34%

Good

2005 20% 54% 50%

2006 20% 59% 47%

2007 16% 44% 43%

Average 18% 56% 43%

I-405 SOUTH 2004 20% 101% 21%

Poor

2005 27% 136% 19%

2006 28% 133% 21%

2007 32% 130% 23%

Average 27% 125% 21%

I-84 EAST 2004 25% 85% 7%

Average

2005 23% 77% 9%

2006 22% 77% 11%

2007 24% 82% 20%

Average 24% 80% 12%

I-84 WEST 2004 37% 55% 86%

VeryPoor

2005 38% 47% 84%

2006 36% 56% 89%

2007 36% 111% 74%

Average 37% 67% 83%

HWY 217 NORTH 2004 16% 41% 31%

Good

2005 17% 49% 42%

2006 24% 58% 53%

2007 21% 50% 47%

Average 20% 49% 43%

HWY 217 SOUTH 2004 29% 94% 58%

Poor

2005 28% 97% 46%

2006 31% 100% 48%

2007 26% 97% 46%

Average 28% 97% 50%

HWY 26 EAST 2004 38% 96% 73%

VeryPoor

2005 35% 75% 73%

2006 32% 89% 67%

2007 33% 70% 83%

Average 34% 83% 74%

HWY 26 WEST 2004 27% 50% 42%

Poor

2005 29% 45% 59%

2006 17% 44% 18%

2007 20% 44% 37%

Average 23% 46% 39%

Table 1: Buffer Indices on Freeways in Portland, Oregon

MPOs StudiedBaltimore Metropolitan Council, Bonneville Metropolitan Planning Organization, Chittenden County Metropolitan Planning Organization, Durham-Chapel Hill-Carrboro Metropolitan Planning Organization, Houston-Galveston Area Council, Indian Nations Council of Governments, Madison Area Metropolitan Planning Organization, Maricopa Association of Governments, Metro, Metroplan Orlando, Metropolitan Council, Mid-Ohio Regional Planning Council, Mid-Region Council of Governments, Montgomery Area Metropolitan Planning Organization, Nashville Area Metropolitan Planning Organization, New York Metropolitan Transportation Council, North Central Texas Council of Governments, Regional Transportation Council of Southwest Washington, San Diego Association of Governments, Tri-County Regional Planning Commission.

Case Study of Portland Freeways

Conclusions• Travel time reliability not used as a

congestion measure• Travel time reliability sometimes stated as

goal or policy of the system• Travel time reliability sometimes stated as a

performance measure for one mode (e.g. transit service reliability)

Content Analysis of Regional Transportation Plans

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Figure 2: I-84 West Buffer Index

Figure 1: I-405 South Buffer Index

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Buffer Index:

Prioritize I-405 South and Hwy 217 South in the PM Peak

Prioritize I-84 West and Hwy 26 East in the AM Peak Worst daily reliability: I-84 West, Hwy 26 East, Hwy

217 South

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Figure 3: Hwy 217 South Buffer Index

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Figure 4: Hwy 26 East Buffer Index