Strategic Highway Research Program 2 Project L07 Identification and Evaluation of the Cost- Effectiveness of Highway Design Features to Reduce Nonrecurrent Congestion Ingrid Potts Midwest Research Institute AASHTO Subcommittee on Design – Annual Meeting July 27, 2010

Strategic Highway Research Program SHRP 2 SHRP 2 focuses on applied research in the following areas: –Safety –Renewal –Capacity –Reliability

What is Reliability? Relatively new term; no single definition SHRP 2 Project L03 (Analytic Procedures for Determining the Impacts of Reliability Mitigation Strategies) developed a working definition: –The level of consistency in travel conditions over time –Measured by describing the distribution of travel times that occur over a substantial period of time (generally one year)

What is Reliability? Traditional approach to assessing freeway performance: –LOS for peak periods New way of looking at freeway performance –Travel-time reliability – What proportion of motorists experience travel times consistent with their expectations?

Reliability Performance Measures How much variability in travel time do motorists experience? How much buffer time does a motorist need? What percent of trips are “on time” or close to “on time”?

Why is Reliability Important? Reliability is an important component of roadway performance (and communicating performance to the public) Motorists have less tolerance for unexpected delay than for expected delay There are costs to motorists associated with planning for unreliable travel times Reliability is important to industries that depend on just- in-time deliveries, and trucking companies that serve those industries Reliability can be improved by implementing strategies to address nonrecurrent congestion

Nonrecurrent Congestion vs. Recurrent Congestion Primary difference is predictability Recurrent congestion –Predictable –Occurs on a daily basis (morning and evening peak periods) –Level of congestion is fairly consistent and anticipated travel times are more reliable Nonrecurrent congestion –Results from random and less predicable events –Varies from day to day and from one incident to the next –Creates unreliable travel times that frustrate motorists

Project Objectives Identify the full range of possible roadway design features to improve travel time reliability and reduce delays due to nonrecurrent congestion Assess their costs and operational / safety effectiveness Provide recommendations for their use and eventual incorporation into design guides

Project Scope Evaluation and assessment of design treatments that: - Address at least one of the primary causes of nonrecurrent congestion Traffic incidents Work zones Demand fluctuations Special events Traffic control devices Weather -Directly or indirectly involve geometric design Inclusion of all facility types of potential interest Freeways | arterials Roadway segments | intersections Signalized | unsignalized Inclusion of all facility types of potential interest

Phases and Tasks State of Reliability- Related Design Practice Highway Agency Experience with Design Alternatives Preliminary Assessment of Design Alternatives Phase I Interim Report Data Gathering Assessment of Design Measures Guideline Development I-1 I-2 I-3 I-4

Phases and Tasks Execute Approved Data Collection Plan Execute Approved Data Analysis Plan Prepare Phase II Interim Report Data Gathering Assessment of Design Measures Guideline Development II-2 II-3 II-1

Phases and Tasks Data Gathering Assessment of Design Measures Guideline Development Prepare Design Guidebook Prepare Draft Final Report Prepare Information Dissemination Plan Prepare /Conduct Five Presentations III-2 III-3 III-1 III-4

What is a Design Treatment? Design treatment: –A highway design feature Directly-design related treatments: –Implemented through physical changes in the highway design that have a direct influence on traffic flow Indirectly-design related treatments: –Not intrinsically highway design features, but have secondary implications related to highway design

Directly Design-Related Treatments Median crossovers Moveable traffic barriers Controlled/gated turnarounds Movable cable median barrier Mountable/traversable medians Extra-height median barrier Portable incident screens Shoulder-use lanes Shoulder improvements for vehicle breakdown and storage Alternating shoulder Vehicle turnouts Bus turnouts Crash investigation sites Emergency access between interchanges Ramp widening Ramp closure Ramp terminal traffic control Ramp turn restrictions Improvements to detour routes Temporary bridges Runaway truck ramps Reduced construction duration Improved work site access Snow fences Anti-icing systems

Indirectly Design-Related Treatments Contraflow lanes for emergency evacuation Contraflow lanes for work zones HOV/HOT lanes Dual facilities Reversible lanes Work zone express lanes Traffic signal preemption Queue jump lanes Traffic signalization improvements Signal timing systems Reversible traffic control devices Ramp metering/flow signals Temporary traffic signals Variable speed limit Electronic toll collection Over-height vehicle detection systems Reference location signs Roadside call boxes Fog detection Road Weather Information System Avalanche warning system Flood warning system Wind warning system

Design-Related Treatments Examples Crash investigation sites Extra-height median barriers Snow fences

Crash Investigation Sites

Extra Height Median Barrier

Snow Fence

Phase II Data Desired: Description Purpose Applicability to nonrecurrent congestion Application criteria Design criteria Examples of use Operational effects Safety effects Costs Objective: To assess design treatments for reduction of delay due to nonrecurrent congestion

Traffic Operational Assessment Objective: to determine traffic operational impact of design treatments on nonrecurrent congestion Application of models from SHRP 2 Project L03 –Freeways in large urban areas –Peak periods Simulation modeling –Freeways in rural and small/medium urban areas –All freeways during off-peak periods

Safety Assessment Objective: to determine relationship between safety and various levels of congestion Three years of traffic operational data (5-min volume and speed data) for freeway systems of: –Minneapolis/St. Paul, MN –Seattle, WA –Los Angeles, CA Crash data from FHWA’s Highway Safety Information System (HSIS)

Phase III Design Guidebook Treatment assessment for each treatment –traffic operational and safety effectiveness estimate or methodology Treatment selection procedure Treatment selection tool Full implementation guidance

Questions?