Do Mobility-Based Performance Measures Reflect Emissions Trends? Congestion and Emissions Co-performance Alex Bigazzi & Dr. Miguel Figliozzi ITE Western District Annual Meeting June

Introduction Congestion and Emissions Co-performance2 Congestion Emissions Rates (per vehicle-mile) Total Emissions VMT

Research Questions Do congestion & mobility performance measures reflect macroscopic emissions trends? If not, what transportation performance measures can be used to better understand and indicate emissions trends? 3Congestion and Emissions Co-performance

Methodology Correlations between emissions estimates & transportation performance measures – Metropolitan level Cross-sections and trends – Corridor level 4Congestion and Emissions Co-performance

5 Performance Measures Congestion and Emissions Co-performance Average speeds * -Travel Time Index, Commuter Stress Index Reliability of speeds * - Buffer Time Index, Planning Time Index Congestion extent - % congested, # rush hours, Roadway Cong. Index Amount of travel - VMT, VHT * Normalized to travel volume (i.e. only sensitive to changes in speed)

Traffic Data Metropolitan-level Estimates – 2011 Urban Mobility Report data tables – 101 U.S. Urban Areas Peak-period speeds, volumes, # travelers, congestion performance… Simplifying assumptions Corridor Estimates – Hourly freeway data – 3 years of counts & speeds over 14 miles 6Congestion and Emissions Co-performance

Emissions Estimates MOVES emissions model (U.S. EPA) Emissions rates a function of speed and facility only (not fleet or time) CO 2 e, CO, NO x, PM 2.5, HC 7Congestion and Emissions Co-performance

Results – Cross-section Congestion and Emissions Co-performance8 LA NY 2010

9 Normalized to # travelers Congestion and Emissions Co-performance 2010

10 Including total travel Congestion and Emissions Co-performance 2010

11 Correlations Congestion and Emissions Co-performance Total Emissions Emissions per Traveler VMT * VHT * Delay VMT / traveler VHT / traveler Delay / traveler Travel Time Index * Commuter Stress Index * Rush Hours per Day * Roadway Congestion Index * % Congestion (lane-miles) % Congestion (VMT) # Peak period travelers No correlation < 0.2 Weak correlation 0.2 – 0.5 Some correlation 0.5 – 0.9 Strong correlation > 0.9 * Weak correlation for PM 2.5 and HC 2010

12 Trends in Portland, OR Congestion and Emissions Co-performance

13 Trends in other cities Congestion and Emissions Co-performance 2000 – 2010

Corridor Study Similar analysis on a 14mi freeway over 3 years Strong correlations between Emissions and VMT, VHT Weak correlations with speed, congestion, and reliability 14Congestion and Emissions Co-performance

15 Corridor Study Congestion and Emissions Co-performance Monthly Data N=31 VMT VHT Delay * TTI * PTI * BTI Daily Data N=621 VMT – VHT * Delay * TTI * Hourly Data N=11,553 VMT VHT Delay Travel Time * No correlation < 0.2 Weak correlation 0.2 – 0.5 Some correlation 0.5 – 0.9 Strong correlation > 0.9 * More correlation for PM 2.5 and HC - Less correlation for PM 2.5 and HC

Conclusions Mobility and related congestion performance measures do not reflect emissions trends at the aggregate level VMT and VHT are the key outputs of the transportation system to understand emissions trends Congestion and Emissions Co-performance16 Mobility measures should not be associated with emissions performance for a city

Future Work Arterial corridor study Vehicle class-separated performance Exposure performance measures 17Congestion and Emissions Co-performance

Thank you! Congestion and Emissions Co-performance18