View
462
Download
0
Embed Size (px)
DESCRIPTION
Citation preview
2010 © CEOs for CITIES 2
KEY FINDINGS
The secret to reducing time Americans spend in peak hour traffic has more to do with how we build our cities than how we build our roads.
2010 © CEOs for CITIES 3
DISTANCE MATTERS
! In nation’s cities largest, typical traveler spends 200hr/yr in peak period travel
! But in best performing cities, travelers spend 40 fewer hrs in peak traffic
! Why? They travel shorter distances
2010 © CEOs for CITIES 4
LONGER TRIP DISTANCES AND SPRAWL SHAPE TRAVEL TIMES
2010 © CEOs for CITIES 5
A VERY DIFFERENT PICTURE
LONGEST PEAK HOUR TRAVEL TIMES
Nashville-Davidson TN Oklahoma City OK Birmingham AL Richmond VA
HOURS 284 252 245 242
RANK 1 2 3 4
UMR RATE 31 38 34 44
SHORTEST PEAK HOUR TRAVEL TIMES
New York-Newark NY-NJ-CT Sacramento CA Chicago IL-IN
HOURS 122 136 163
RANK 46 48 51
UMR RATE 14 23 21
2010 © CEOs for CITIES 6
ROADMAP
1. The Urban Mobility Report
2. Travel Time Index is flawed concept
3. UMR overestimates congestion
4. Fuel economy estimates contain errors
5. Developing better measures
2010 © CEOs for CITIES 7
THE URBAN MOBILITY REPORT
! Produced since 1982 by Texas Transportation Institute
! Provides estimates and rankings of congestion
2010 © CEOs for CITIES 8
UMR CLAIMS
! Congestion is a big problem – 46 hrs of delay per person per yr
! It wastes lots of energy
! It’s getting worse
! It costs us a lot of money – $750 per person up from $290 in 1982
2010 © CEOs for CITIES 9
UMR REALITY
! Impact of distance on travel times ignored
! UMR rates areas “less congested” even if residents have to travel farther and longer
! Congestion estimated from unattainable ideal
! Speeds estimated from inaccurate model, mechanically converting higher volumes into slower speeds
! Other evidence shows commute times have not increased
! Fuel economy incorrectly estimated, overstating costs
2010 © CEOs for CITIES 10
A FLAWED CONCEPT: THE TRAVEL TIME INDEX (TTI)
! How much additional time does it take to travel a given distance at peak vs off-peak
! Example: – Trip takes 20 min off-peak (free flow) – Trip takes 25 min at peak – TTI = 25/20 = 1.25 – 5 min of delay
2010 © CEOs for CITIES 11
PROBLEMS WITH TTI
! An unrealistic baseline – No one expects or can achieve zero delay/free-flow in the peak hr
! TTI ignores variations in travel distances among metro areas
2010 © CEOs for CITIES 12
IS CHICAGO TRAFFIC REALLY WORSE? COMPARISON Average Trip Un-congested Travel Time Delay Total Travel Time TRAVEL TIME INDEX
CHARLOTTE 19mi
38.4min 9.6mi
48.0mi 1.25
CHICAGO 13.5mi 22.8mi 9.8min 32.6mi 1.43
2010 © CEOs for CITIES 13
UMR OVERESTIMATES CONGESTION
! No direct observation of travel time
! A bad model for estimating travel time
! UMR results don’t square with other measures
2010 © CEOs for CITIES 14
WEAK BASIS FOR SPEED ESTIMATES
2010 © CEOs for CITIES 15
CHECKING UMR VALIDITY
! Do UMR estimates square with other data on variations in travel over time and space?
– Inrix: Real time speed data – NHTS: Comprehensive travel survey data – Census/ACS: Reported journey-to-work travel time data
2010 © CEOs for CITIES 16
NATIONAL SURVEY SUGGESTS TRAVEL TIME, ADJUSTED FOR DISTANCE, ACTUALLY DECLINED
2010 © CEOs for CITIES 17
UMR NOT CONSISTENT WITH INRIX
The average UMR estimate in 70% higher than the average INRIX observation: UMR = 1.24 INRIX = 1.14
2010 © CEOs for CITIES 18
FUEL CONSUMPTION ESTIMATES BASED ON OUTDATED STUDY
! RAUS study done in 1981
! Data: 1973-76 GM cars av 13.6mpg
! Fuel economy estimates
“The above relationship is good only for speeds up to
about 35mph”
2010 © CEOs for CITIES 19
UMR v. DOE FUEL ECONOMY CURVES
2010 © CEOs for CITIES 20
TOWARD BETTER MEASURES OF URBAN TRANSPORTATION SYSTEMS
TWO KEY TASKS ! Correcting the UMR
! Developing new measures that emphasize accessibility
2010 © CEOs for CITIES 21
CORRECTING THE UMR ESTIMATE
! Recompute UMR, assuming – Realistic baseline
– Better travel time data (Inrix) – Lower travel time costs – Drop fuel model
! Reduces UMR cost estimate 70%
! UMR overstates by $49 billion
2010 © CEOs for CITIES 22
A NEW FOCUS
! Shift to accessibility measures
! Start with shorter distances actually traveled in many metro areas
! Use a realistic baseline – What is actually attained in best of class metro areas – Look at 90th percentile performers
! Quantify time, energy, and economic costs of sprawl-lengthened commute travel
2010 © CEOs for CITIES 23
THE ROLE OF LONGER TRIP DISTANCES
2010 © CEOs for CITIES 24
THE PAYOFF
! If every one of the top 50 metro areas achieved same level of peak hr travel distances as best performing cities, their residents would drive about 40B fewer mi/yr and use 2B fewer gal of fuel, at savings of $31B annually.
2010 © CEOs for CITIES 25
SOME CITIES HAVE MADE PROGRESS THE UMR VIEW: Congestion got worse Travel Time Index
1982 1.07
2007 1.29
THE REALITY: Trips and travel time got shorter Average Trip Travel Time
1982 19.6mi 53min
2007 16.0mi 43min
2010 © CEOs for CITIES 26
BUILDING A BETTER MEASURE
! Emphasize access to destinations
! Add measures of land use & trip distance
! Incorporate better data
! Adopt open, multidisciplinary process
! Aim to guide policy and assess investments
2010 © CEOs for CITIES 27
CONCLUSIONS
! The Travel Time Index (TTI) is a misleading guide to assessing transportation system performance and costs and inherently rewards sprawl and penalizes compact development
! The UMR methodology is flawed, and its results can’t be reconciled to real world observations
! Sprawl, not congestion, is the bigger source of time loss, energy waste and excess costs in most metro areas
! New measures that emphasize accessibility should guide our transportation policy