Fourth AnnualPreserving the American Dream Conference

AtlantaSeptember 16, 2006

Reforming Public Transit –Transit and Congestion Relief

Thomas A. Rubin

Reason FoundationGalvin Mobility Project

• A series of professional papers on mobility

• First ones have been published, available at:

http://www.reason.org/transportation/

• Many more now in works

• I’m doing one on the relationship between transit and traffic congestion

Process

• Test hypothesis: Transit has a Significant Positive Impact on Traffic Congestion (as transit usage goes up, congestion decreases)

• Study Population is U.S. Urbanized Areas• Transit Usage data from National Transit

Database (NTDB) (independent variable)• Traffic Congestion data from Texas

Transportation Institute (dependent variable)

Transit Usage Data

• NTDB data from Florida Transit Information System (FTIS)

• Allows single inquiries for multiple data items for multiple years

• Data elements selected:– UZA Total Unlinked Passenger Trips– UZA Total Passenger-Miles– UZA Total Light Rail Unlinked Passenger Trips– UZA Total Light Rail Passenger Miles

Traffic Congestion Data

• Texas Transportation Institute (Texas A&M), Transportation “Travel Time Index” (TTI) (Schrank and Lomax)

• TTI is ratio of time required to travel at peak hours:time required to travel with free-flow conditions

Data

• Data available from both sources for years, 1984 to 2003, inclusive – 20 sets of data for each UZA

• TTI UZA’s – 69 Total:– 13 Very Large (3,000,000 < population)– 26 Large (1,000,000 < population <

3,000,000)– 30 Medium (500,000 < population <

1,000,000)

Data Quality/Quantity

• Both NTDB and TTI are generally good, not perfect

• In general, quality of data improves as present day is approached

• 69 UZA’s with 20 years of data each; 1,380 sets of data

Process:

• Run various simple and multiple regressions to test alternative relationships

• Test for each UZA individually and for entire population of 69 UZA’s

• To do test for all 69 UZA’s, data had to be “normed”

Issues with TTI

• See Cox & O’Toole, The Contribution of Highways and Transit to Congestion Relief: A Realistic View, Heritage Foundation, Backgrounder #1721, January 27,2007:http://www.heritage.org/Research/UrbanIssues/bg1721.cfm

• Relatively low correlation with actual Travel Time (ACS)

16

20

24

28

32

AC

S H

om

e-W

ork

Co

mm

ute

Tim

e (

Min

ute

s)

1.00 1.10 1.20 1.30 1.40 1.50 1.60 1.70 1.80TTI Travel Time Index

SPR

ROCH

DAY

RICH

TOL

TUL

HART

NH

FRES

ALL

EP

BIRM

NASH

OMA

JAC

HONO

RD

MEM

SARA

SLC

BRDG

CHAR

TUCAUSCLEPIT

KC

NO

VBSA

IND

ORL

TSP

MSP

SJ

RSB

BALT

SEA

LV

DEN

SD

PHILBOS

DFW

NYC

HOU

MIA

ATL

DC

SFO

CHI

LA

Medium Large Very Large Least Squares

MAJOR U.S. URBAN AREASTTI vs ACS Home-to-Work Travel Time

r-squared = .55

Interim Report

• I had my associate do the analysis for two UZA’s to test the data

• Figured, what-the-heck, do the regressions and see what we get

• Overall expection? Not much connection – congestion is basically a supply-and-demand thing and transit is just a small percentage of total transportation in most UZA’s.

• So, here’s the results – for Portland, Oregon

(May I have a drumroll, please?)

Greater Portland UZATotal Transit Passenger-Miles and TTI

150

200

250

300

350

400

450

500

1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

Year

Pass

enge

r-M

iles

(Mill

ions

)

1.00

1.10

1.20

1.30

1.40

1.50

TTI V

alue

Passenger-Miles TTI

r-squared = .86

THERE YOU HAVE IT FOLKS: PROOF

POSITIVE THAT TRANSIT CAUSES

CONGESTION

not

Well, Why Not?

• Rule 1: “Correlation is not causation.”

• 20 data points for one UZA is just a bit thin for drawing this type of conclusion.

• Most important, what possible direct causation could there be between, all else equal, an increase in transit usage – presumably, taking vehicles off the streets – and congestion getting worse?

But, All Else Isn’t Equal in Portland

• First Portland Light Rail Line was largely funded with Federal “Interstate Transfer” funds – Portland (or, more properly, the Mayor of Portland, with assistance from other officials) decided to give up an urban Interstate that had already been approved and funded to build this line.

• An urban freeway has several times the “transportation work” capacity than any light rail

But, All Else Isn’t Equal in Portland II

• Building this light rail line required taking out a pre-existing HOV lane from a freeway that had higher transportation work values than the light rail line

• Building light rail on surface streets has reduced road capacity on these arterials and made crossing movements more difficult

But, All Else Isn’t Equal in Portland III

• Portland (Metro, Tri-Met, State, et al) have largely decided to not implement road capacity improvements – as demand increases

• Portland et al have adopted LOS “F” as the official target – while this is the result in many UZA’s, at least the others are officially trying to do better, not worse

So, can transit actually cause congestion to increase?

No, not by itself.

But, as a component of an officially adopted program of “interesting” transportation

decisions, a case can be made.